Natural philosophy improven by new experiments touching the mercurial weather-glass, the hygroscope, eclipsis, conjunctions of Saturn and Jupiter, by new experiments, touching the pressure of fluids, the diving-bell, and all the curiosities thereof : to which is added some new observations, and experiments, lately made of several kinds : together with a true relation of an evil spirit, which troubled a mans family for many days : lastly, there is a large discourse anent coal, coal-sinks, dipps, risings, and streeks of coal, levels running of mines, gaes, dykes, damps, and wild-fire / by G.S.

NATVRAL PHILOSOPHY Improven by NEW EXPERIMENTS . TOUCHING The Mercurial Weather-Glass , the Hygroscope , Eclipsis , Conjunctions of Saturn and Jupiter . BY NEW EXPERIMENTS , Touching the Pressure of Fluids , the Diving-Bell , and all the curiosities thereof . To which is added , Some New Observations , and Experiments , lately made of several kinds . TOGETHER , With a true RELATION of an Evil Spirit , which troubled a Mans Family for many days . LASTLY , There is a large DISCOURSE anent Coal , ●oal-sinks , Dipps , Risings , and Streeks of Coal , Levels , Running of Mines , Gals , Dykes , Damps , and Wild-fire . By G. S.

Ars longa , vita brevis .

Printed in the Year , 1683. And are to be sold by Gideon Schaw Bookseller , at the Sign of the Bible , in the Parliament-Closs , in Edinburgh .

To the Right Honourable S r. JAMES FLEMING , Lord Provost of EDINBURGH , George Drumond , David Lindsey , Iames Nicolson , and GEORGE SINCLAR Bailiffs , Archibald Hamilton , Dean of Gild , Thomas Young , Thesaurer , William Borthwick , Deacon Conveener , and remanent Members of the Honourable Council of the said Burgh ; In all Humility offers and didicates this Philosophical Tranasaction , GEORGE SINCLAR Professor of Philosophy and Mathematicks . May it please Your Lordship , and the Honourable Senate ,

I Present you with a mean Oblation , less than the Widows Mite , but with a willing mind . 'T is all I can afford at present . Farre li●abit , qui non habet , thus : Who wants Frankincense , must sacrifice with Bear-meal . I have sometimes offered more to others , who were not so deserving . I still remember how kindly the Council treated me for some Years ago . when I taught the Mathematicks at Edinburgh ; and what a singular Obligation they conferred upon me after , when I was employed to search out a well , which by good Providence I lighted upon , which is now a Well-spring of Happiness to the Good-Town . I made several Observations , with a most accurate , and exact Level ; but especially one from the highest Ground in the Castle , in the Evening towards the Fountain , by the help of a Light there , on the 29. of May , 1674. which gave infallible assurance to the Magistrates , that the Source was 200. Foot higher than the Weigh-house , and great encouragement to the Council to begin the Work . It is registrate in Scripture , as one of the great Acts of Hezekiah , that he made a Cistern , and a Condu●t , and brought Water into the City of Jerusalem . This work will be extant among the Annals and Chronicles of the City , of things done from Year to Year , to all Generations , which is the glory also of the succeeding Magistrates . But your wisdom and prudence in governing the City , and composing all Differences , and setling all Matters every day so happily , is of far greater moment .

This Transaction explains the Weather-Glass , and Hygroscope , which are in great esteem , even among Kings , and Princes . His Royal Highness put no small value upon that which I presented to Him . Non equidem tali me dignor honore .

I now crave pardon , that I have adventured to prefix your Names to the Frontispice of this mean Pamphlet , between which , and your incomparable Merits , there is no proportion . All I can do , is to pray , that your Lordship and Council may live to be , as you are , the glory and credit of the Place , and that you may slowly , yet surely exchange at last , this Mortality with Immortal Life . This I fervently wish , while I am

Your Honours most humble , and much obliged Servant , GEORGE SINCLAR . Leith , Ianuary 9. 1683.

The Explanation of the Weather-Glass .

I Have set down the Theory of the Weather after this manner . In the first , and upmost Station , thirty Inch and a half , above the Cistern , is Long Fair , or Most pleasant Weather , as the Poet sings , Totus & ille dies , & quin ascentur ab illo , Exactum ad mensem , pluvia ventisque carebunt . This day and all , which after it remain , F●r th●●ty day● , sha●l want both Wind and Rain . The Metal being at this height , which I rather find to be in Winter , than in Summer , the Heavens are clear : yet sometimes covered with dry and gray Clouds , but not the least appearance of Rain . Nothing for several days after , but setled calm Weather , as dry and hard Frost in Winter , with a clear Sky : sometimes the Air most pure , and clear without Frost . Here it was upon Thursday , October 26. 'T is seldom so high , because we in this Countrey have not often , a most pure , and clear Air , as in France , and other parts of the World ▪ If the Metal ascend to this Station , it is an evident token , that the Glass , is right mounted , and adjusted .

I call the second Station , which is half an Inch lower , Fair , or Dry and Fair. ●ace serenato clar●m juhat emicat ax ▪ P●●gatusque nitet di●●ussis ●u●ibus ●●ther . Behold a Ray , tha● 〈◊〉 breaks forth from se●●n● Hea●en And purged Sky doth shine , all Cloud 〈◊〉 that 's been . The Quick-silver being at this Station , the Weather is good ; but not so setled , especially in the Winter-season . I have oftentimes observed a small thin showre of Rain to fall , for some Hours together , from the lowest Region of the Air , as a thick Dew or Mist , but immediatly after , the Day became Clear and Fair , the Air being under a strong disposition to be so .

The third Station , half an Inch lower is Changeable , sometimes Fair , sometimes Foul , sometimes Frost , sometimes Thaw , sometimes Sleet , sometimes Snow , sometimes Wind , sometimes Calm .

Nun● pluit , & clarus , nune Iupiter aethere surgit . Sometimes ●oul Jove , doth wring the Clouds for Rain , Sometimes fair Jove , appears in Heaven again .

The fourth Station is Rain , or Rainy Weather ; not that it Rains always , but that there is a strong inclination in the Air , to be Rain .

— Madidl● Notus evolat all● , Terribilem pleca tectus caligine vultum , Barba gravis nimbi● , can●s ●uit unda capillis . Out flyes the South , with dropping Wing● , who shrouds , His 〈◊〉 aspect in the pitchy 〈◊〉 . His white● air streams , his bea●● b●g . ●●●oln with Shor●● ▪ M●●ls bi●● hi● bro● , Rain from his boso● pu●●●es ,

I call the fifth Station , Much Rain , or Very Foul , as in the Summer , or Winter-time , when Rain is accompanied with strong S. W. and W. Winds . This is bad Weather indeed , both by Sea and Land . — Et den●i ●unduntur ●● aethere n●●bl ▪ Ecce cadunt ●argi , reselusia nubibu● , imbre● Inquetreom credas totum descendere coeluth . 〈◊〉 of Rain , are poured from the Heaven , Waich●●ken Phenus , and his peir●ing Beams . 〈…〉 great 〈◊〉 did fall , Some thought the Heavens to Sea , were tu●bled all . To this Station did the Mercury fall down , on Monday , November 6. and Sunday night , November 19 , being two Inch lower , than October 26.

The sixth Station is Stormy , the worst of Weather in this Country .

Tum mihi ●ae●ule●● , supra caput astitit imber , N●ctem Hyememque ●erens , & inhorruit und● tenebris . A purpur● showre did Canopy my head . Dark Winter came , and waves grew black indeed ▪

I have subjoyned in the last place Tempests , or Hirricanos , which do not fall out in this Country . They are lively described by the Poet.

— Acvent● , velut agmine f●cto , Qua data por●●●unt , & terras turbine per●●●nt . Incubuere mari , to●●mque a sell●us im●s . Una , Eu●u●que , No●●sque en●nt , cre●erque procel●●a Africus , & vasto● volvunt ad littora fluctus ▪ Tempect●●●ine more ●urit , ton●●●●que tren●seunt . Ardua terra●um , ●●●pique & littora circum . — Winds at his mutinous ●ands Force their own way , and thunder through the strands . They take the Sea , Eurus and Notus raves , And stormy Africus from deepest c●ves . When Temp●storage , and Joves great Cannons rea● , The Mountains quake , the Plains , and every Shoar .

The first Rule is , the further up the Metal goes , the Weather inclines to be the Fairer , and the further it falls down , it inclines to be the Fouler . Secondly , When it is heighest , Fair Weather is universal , when it is lowest , Foul Weather is universal . Thirdly , 'T is not so much Fair or Foul Weather actually , which influences the Quick-silver , as it is the disposition , and inclination of the Weather , to be Fair , or Foul. Note , That N. E. and E. Winds , even with Ra●n , do raise the Mercury , and keep it up sometimes beyond ordinary . And as it shews the nature of the Weather , so it foretells ; which is the great excellency of it , sometimes a day , sometimes two , sometimes three or four , before any change of Weather come . The Metal rises and falls quickly , when Fair or Foul Weather is nigh at hand . It doth not so much foretel Winds , as it is actually influenced by them , when they blow , in causing the Metal subside and fall down . 'T is said , that the Ladies and Gentle-women at London , do Apparel themselves in the Morning , by the Weather-Glass . Whatever be in this , 't is certain , that when a Man riseth in the Morning , he may know infallibly , what sort of Weather , will fall out ere Night . It is not possible to make it unerring , unless it be mounted , and set up by a skilful Hand , which few or none can do . The inclosed Weather-Glasses , are Ten Dallers , the open ones Thirty Shillings , which are as true . None from Abroad are so accurately made . Neither any such are sold , at so easie a rate . They may be transported , and carried to any part of the Country , and there set up , by my Directions .

The Explanation of the Hygroscope .

THis second is a curious Invention , which I call the Hygroscope . The The name is made up of two Greek words , Hygros Wet , and Scopeo to view or consider : because we know by it , the several degrees of moisture , and dryness in the Air. It is mean to look upon , being but the Awin , and Beard of a Grain of Oats . It is Twisted , and Twined by Nature , as the Lute String , or a Silk Cord is twined by Art . It is secured within a round Box , whose inside is divided into 24. equal parts . There is affixed to the top of it , a small slender Glass-Index , which goes about with the Awin , as it is altered with the moisture , or dryness of the Air. The motion is direct , or right about , following the course of the Sun , with moisture , and retrograde , or left about , with dryness . It is likewise stationary , or standing , when the Air is setled , as to wetness , or dryness . It is of all of all things , in the Universe , so far as I know , most affected and sensible of humidity and s●●city . Many curious Philosophical Questions do arise from its several Operations ▪ which would trouble Oedipus himself , to resolve . I have found the Index , from Wet Air in extremity , to Dry Air in extremity , make six Revolutions . For this cause , I have contrived a little Broad , with six Circles upon it , or rather Spirals , divided equally into 24. parts , as the inside of the Box is , by the help of which , a Man may trace the motion of it , all the Year over , most easily , whether it be Direct , or Retrograde . You will find these advantages by it . Wet Air in extremity , Dry Air in extremity , Air equally moist and dry , Wet Air , Dry Air. It discovers the least difference of Air between one Room and another . It is much influenced with Winds from the North , especially in Frost , which make it Retrograde , and with Winds from the South , which make it Direct and move right about . In a Years time , it makes several Revolutions . The motion is most sensible , for sometimes in one Night , it will alter 90. Degrees , o● the fourth part of a Circle . It not only shews the present temperament of the Air , which is a great advantage , but foretels . Nay , which is admirable , I have found it sometimes foretel Fair Weather , when it was actually Raining . It keeps a correspondence with the Weather-Glass . There is great difficulty to know what Revolution it is under , from Wet Air in extremity , or from Dry Air in extremity , for fixing the Brass-Pin in its own proper Circle . The Husk or Hool , of the Mouse-Pea , ( as we call it ) or the Wild Vetch , will make a Hygroscope , but it is somewhat dull and slow , and goes not so oft about , yet very sensible of the Wetness , and Dryness of the Air. When the Index of the Hygroscope , is altered by the Weather , it keeps not a continued motion , but sometimes moves backward , and sometimes forward ; yet at length perfects its course right about , in so many Months , and returns again in so many . Among the many difficulties which occur , this is one , What is the reason , why the Awin goes alwayes right about with Moisture , and left about with Dryness ? To say , that it is so ordered by Nature , is ridiculous . The same difficulty we find in the Shells of Snails , whose Screw , and Spiral line , goes right about , with the Sun , and in the Shells of Sea-Snails , commonly called Buckies . Some affirm , that upon the South of the Line , the Shells of these Creatures , are screwed left about , which is worthy of observation . 'T is easie to give the reason ▪ why a Lute String turns about such a way with Moisture ; because , while it was twined by the Artist , the Wheel or Spindle went such a way about , wherewith he twisted it . But who can say the like of the Awin , seing the great Artist is GOD , and Nature , whose working and manner of working is unknown to us . 〈◊〉 be asked , What way goes about the Hool of the Wild Vetch ? I answer , which is a notable Speculation ▪ The one Hool , goes right about with the Sun , by Moisture , as the Awin doth , and consequently left about , with Dryness . But the other goes right about with Dryness , and left about with Moisture , contrary to the motion of its fellow Hool . This is seen sensibly , by holding them nigh the Fire . The same holds true , in the two Hools of the Right Pea-cod . I suppose that the Hools of Brom-seed , may do the like . Another Experiment I made with the Hygroscope , in placing it , within the Receiver of the Air-pump . At the very first Exsuction of the Air , the Index moved left about most sensibly , and by the several Exsuctions , which were made one after another , it advanced , half a Circle about . It had been easie to have made it go right round once , if I had continued Pumping . Here is a Phenomenon to be salved , and well worthy the pains of a Virtuoso . But because some may think , I have spoken too much of a thing of small concern , I shall therefore say but one word or two more . That even upon the obscurest , and meanest of the Creatures , the LORD hath impress'd an Indelible Character , of His Wisdom and Skill . Though we cannot well know , for what use and end , the Oat-Grain hath an Awin , and why it is twisted , yet we must remember , that GOD , and Nature , never made any thing in vain . Do not undervalue it , because it is meanly let out ; for there is in it a Pearl of great price ; Christopherus Sturmius a German , a great Virtuoso , and famous Mathematician , makes honourable mention of it , in his Writings , which he hath taken from my A●s Nova & Magna , as he hath done many other Curiosities and published them to the World , not as his own Inventions , but as mine : which by the way , gives a notable check to my old Adversaries , who with the Bed●lls Gown about their heads , endeavour'd to make the World , in their beggarly Pamphlet believe , th●● all my Philosophical Experiments were Untruths and Lies . Sed non est remedium adversus Sycophantae mo●sum ; there is no cure or remedy against the bi●ng of Slanderers . Mr ▪ Boyl did not think so as witness his Experiments ●ouching Flame and Air. They are sold for Six Shillings .

A short account of the late Comets , and of some Eclipsis .

ANno 1652 , An obscure Comet appeared in the beginning of Winter , seen in the forenight , nigh to the Constellation of Taurus . It did not continue long ; yet Lilly that old Astrologer made it very prodigious .

A second , far more glorious , appeared in the beginning of December , 1664. It raise before the Sun several Mornings , with a long Ray , pointing towards the West . First then , it was Cometa Barbatus , the Ray going before the Star . It had a very swift motion towards the West , inclining upward , till it came the length , to be in opposition to the Sun , on the 19. of December , where it appeared Cometa Crinitus , without a Ray. Being under a swift motion , it advanced more Westerly and upward , and was seen clearly upon Sunday night , December 25. with a long Ray , pointing towards the East , which made it Cometa Caudatus , the Train following the Star , and setting after the Sun . This made many believe , that there were two Comets . It evanished a little below the Rams-head , after it had continued from December 8. 1664 , to February 8. 1665.

A third was seen , the same Year 1665 , in March , and continued till the 7. of April :

A fourth was seen in the middle of April , 1677 , about 11. a Clock at Night . It continued but a short time .

The fifth seen over all Europe with admiration , appeared first clearly to us , December 14. 1680. It continued till February 8. 1681.

The sixth Comet , was seen Thursday Night , August 17. 1662 , in the North , about 11 a Clock at Night , in the second Foot of the Great Bear . It had a swift motion towards the West , declining from the North. It past over above the back of the Lion , and under Coma Berenices , under Arcturus , crossing Bootes forefoot , towards the Aequinoctial , and thence towards the Beam of the Ballance .

Anno 1682 , Saterday night February 11 , about 11 a Clock , a prodigious Eclipse of the Moon . The total darkness , continued an Hour and a half , measured by the Pendulum Clock . The Eclipse , was not only Total , but Central , that is to say , a straight Line might have been drawn almost , from the Centre of the Moon , thorow the Centre of the Earth , to the Centre of the Sun . The Moons face was red as Blood , especially about the midle of the Eclipse . Compare it with Ioel 2 : 10. Acts 2.19 , 20. Isa. 13.10 . Ezek. 32.7 , 8. Mat. 24.29 . Luk. 21.25 .

Anno 1662 , December first , all the seven Planets met in that one Sign of Sagittarius , the Archer .

Anno 1663 , Friday October 9. A conjunction of Saturn and Iupiter in the 13. deg. of Sagittarius .

Anno 1661 , April 23. Mercury did Eclipse the body of the Sun .

This Year 1682 , a conjunction of Saturn and Iupiter in the Sign Leo , on the 23. of October , which is the fourth Conjunction , since they entered the fiery Trigon , which are Sagittarius , Leo , and Taurus .

Anno 1679 , April 2. Two Suns seen in the Firmament , in the Fore-noon , in East-Lothian . Extraordinary Foul-Weather followed this Parelia .

Anno 1598 , February 25. a total Eclipse of the Sun , so that the Stars were seen . It is to this day called the Dark Saterday .

Anno 1652 , March 29 , in the Fore-noon , a total Ecipse of the Sun , so that the Stars were seen likewise . It is commonly called the Dark Monday .

Simsines Philadelphus , a devout Man , and learned Astrologue , writes in his Book , which he published Anno 1626 , and dedicated to Frederick King of Bohemia , that there never happened , any great Change or Alteration , in any State or Kingdom , in Europe ; but what hath been accompanied , with a Conjunction of Saturn and Iupiter , under some Trigon or other . And reckoning over all the ten Principalities and Dominions , which have been in Britain , since the Year of the World 3618 , he comes at last to the Year 1603 , in which , Saturn and Iupiter , after they had returned into the Fiery Triplicity , being the seventh time from the Creation , fell in Conjunction in that Fiery Sign Sagittary , in the Month of December . Here he takes occasion , to mention King Iames , his succeeding to the Crown of England that year , of whom by the way , take this Distichon , or two Verses . Cura Del , vasemque lab●r , sapientia secii , Pax quoque , mulavit , regna quaterna Polo . Gods Care , the Ag●s Wit , Peace , Prophets Pairs , For Kingdoms fou●● in Heaven a kingdom gain● . And shews , that this , which he calls Regnum Scotorum , the Dominion of the Scots , and tenth Principality , was received , by these two superior Planets , in their Greatest Conjunction . Note , That these Conjunctions , are sometimes propitious , as this was . It was likewise favourable to the Hollanders , who were treated with a Free State Anno 1607. And concludes , with these remarkable words . Et non jam expectanda est gravior aliqua mutatio in Britannia , nisi continua Consanguinearum successio ; siquidem Periodi huic regno transierint . Nam à primo Rege Bruto usque ad presentem annum elapsi sunt anni 1978. That is , And now there is not any greater Change to be expected in Britain , but a continued Succession of the Nearest in Blood ; for truly the Periods to these Dominions are gone , and past over . Because from the first King Brutus to this present Year , there are past 1978 Years . This Brutus was the first King of the Britains , who began his Reign in the Year of the World 3618 , under the Aerial Trigon , and Conjunction of Saturn and Iupiter , in the Sign Gemini .

For the better understanding , know that the twelve Signs are divided into four Triplicities , which are called by Astrologues Trigons . The first Trigon , is called the Fiery Trigon , which contains , Aries , Leo , and Sagittarius . The second is the Earthy , which contains , Taurus , Virgo , and Capricorn . The third is the A●rial , which contains , Gemini , Libra , and Aquarius . The fourth is the Watery , which contains , Cancer , Scorpius , and Pisces . If it happen , that Saturn , and Iupiter be in Conjunction this Year in Leo , there next Conjunction , will happen , twenty Years after , or truly , 19 Years , 315. Days , and 19. Hours after , in Sagittarius . From Sagittarius to Aries ▪ from Aries to Leo , and so in round till 198. Years , and 236. Days passing , they make a Transit into a New Trigon , so that the Revolution of one Trigon consumes almost 200. Year . My Author speaking of that Conjunction , which fell out Anno 1643. in Aries , says , Alicujus Imperii , vel Regni , revolutionem portendit . It betokens a change in some Empire or Kingdom in Europe , which really came to pass after , as all know .

A Journal of the late great Comet under the Latitude of 55. deg. 54. m. 30. s.

ON the 22. of November , 1680 , it was first seen at Plimmouth , in England , soon in the Morning . Upon the 14. of Decem. being Tuesday , it appeared first to us , in the Constellation called Antinous . This Antinous , was of the Country of Bithynia , who for his vallant deeds , was Canonized , and added to the number of the Gods , and placed in Heaven , in Capricorn , in which Sign the Sun at that time was , deg. 3. m. 39. This Comet had a Ray , which went straight up from it , about 60. Degrees in length . This Night , at 5. a Clock , it had 5. deg. of Altitude , above the Horizon . The Ray was broader , and more spread out above , than below . In the Head was a clear Star , of a whitish colour . The middle of the Ray covered the lesser Star in the Gorge of the Eagle . The Poets feign , that this was the Bird , that flew up into Heaven with Ganymedes , whom Iupiter loved so dearly ; for which good service , he placed the Bird among the Stars ▪ Wednesday , Decemb. 16 ▪ at 5. a Clock at Night , the Blazing-Star , seemed to be higher , by 3. degrees almost , and more Easterly . For this Night , the middle of the Ray eclipsed the bright Star , in the neck of the Eagle , which is the greater , and more towards the East ; but somewhat lower . The Pinion of the lowest Wing of the Swan , did terminate the extremity of the Train . On Thursday Morning following , about 5. a clock , the Ray was seen above the Horizon : at least much of it , not straight up , out sloping towards the North. At Night , December 16. about 5. a Clock , the Star had about 11. degrees of Altitude above the Horizon . At which time , the Ray had passed by , both the two forementioned Stars in the Neck of the Eagle , it being far more Easterly . It was not seen , till Sunday at Night , December 19. at which time , it was yet further up above the Horizon , the middle of the Train , covering the Constellation , called the Delphin . Neptune the god of the Sea , greatly desired , to match with Amphitrite , who being modest , and shame-faced , hid her self . After long search , he sent the Delphin , who found her out , for which good service , he placed this Fish in the Heaven . It was not seen till Decemb. 24. at which time in the Evening , it was past the Aequator , and had about 7. degrees of North Declination , and was in the 20. degree of Aquarius , not far from the Nose of Pegasus . The Night following , being Saterday , Decemb. 25. It was not seen . Sunday Decemb. 26. It was seen , at 5. a Clock , with 37. degrees of Altitude . The middle of the Ray , did cover the right Knee of Pegasus . The end did terminate in the very Zenith , between Cassiopea , and Perseus . After this the Star was not seen , till Ianuary 2. 1681. This Night the Ray , past thorow the Belly of Pegasus . Perseus did terminate the end of it . Pegasus the winged Horse , was bred of the blood of Medusa , after that Perseus had cut off her Head . Bellerophon made use of this Horse , and having performed some valiant deeds here on Earth , endeavoured to fly up to Heaven on his Back ; but being amazed by looking down to the Earth far below him , he fell from his Sadle . Pegasus , notwithstanding continuing his Journey , came at last into Heaven , and there obtained a place among the Constellations . Monday Ianuary 3. the Comet was distant from And●omeda her head , about 5 degrees , but somewhat more Westerly . Upon Tuesday Ianuary 4. the Comet , was nearer to the Head of Andromeda , but somewhat lower . Ianuary 5. being Wednesday , the Comet was within a degree and a hal● , of the Head of Andromeda , but a little lower , and more Westerly . Thursday Ianuary 6 , the Comet was higher , than the Head of Andromeda , but more Easterly . The Ray passed thorow between the two bright Stars , in the Belt of Andromeda . Perseus did terminate the end of it . This Night , the Ray was 30. degrees long . Friday Ianuary 7. it was not seen . Saterday Ianuary 8. the Head of the Comet , was within one degree , of the Star , which is in the lest Shoulder of Andromeda , but a little higher , and more Easterly . The Ray was 22. degrees extended . Sunday Ianuary 9 , the Comet was yet higher , by one degree , and more Easterly , than the foresaid Star . The bright Star in the South Foot of Andromeda , did terminate the end of the Ray. It was not seen , till Friday Ianuary 14 , on which Night , it was about mid-way between the bright Star , in the Belt of Andromeda , and the point of the Triangle , but somewhat higher to the said bright Star . Andromeda was the Daughter of Cepheus , and Casstopea , and the Wife of Perseus , who , by the favour of Minerva , was taken up into Heaven , and placed among the Constellations . Saterday Ianuary 15 , the Comet was somewhat higher , than it was the Night foregoing . Tuesday Night Ianuary 18 , it had this position with the Triangle , according to the first Figure . Thursday Night Ianuary 20 , it had this position with the Triangle , according to the second Figure . Thursday Night Ianuary 27 , it was thus placed , according to the third Figure , about one degree , and a half above the Eastmost Star in the B●se of the Triangle . The Ray was about 8. degrees in length . The end of it , was bounded with the Eastside of Medusa's Head . The Triangle was placed in Heaven , in honour of the Geometricians , among whom , the Triangle , is of no small importance . Others say , that it was placed there by Mercury , that the Head of the Ram , might be the better knowen .

Saterday Night Ianuary 29 , the Comet , was in a right Line , with the first Star of Aries , and the bright Star in Medusa's Head . And in a right Line , with the West-most Star , in the Base , of the Triangle , and the Pleiades . It was the matter of 8. degrees distant from the East-most Star , in the Base of the Triangle , further up , and more Easterly .

Perseus , the son of Iupiter , and Danae , kill'd the Monster Medusa , and cut off her Head . Her golden Hairs were turned into Serpents by Minerva , for polluting her Temple with Neptune . Whosoever looked on her after this , were turned into Stones . Perseus , falling into trouble of Mind , for killing accidentally , his Grand-father Acrisius , was taken up into Heaven , by his Father Iupiter , and placed there , with Medusa's Head in the one Hand , and the Sword in the other .

Wednesday February 2 , the Comet was scarce discernable , yet further up in the Heavens , and more towards the East , than before . Tuesday Night , February 8. being the last time , it was seen , nothing appeared distinctly , save a small short Ray. This Night , it had 20. degrees of North Latitude , from the Ecliptick . It had 46. degrees of Longitude , from the first point of Aries . It was distant from Medusa's Head , 5. degrees . It was distant 14. degrees , from the West-most Star , in the Base of the Triangle . It was 10. deg. 30. m. from the bright Star in Andromeda's foot . It was 16. degrees , from the first Star in Aries . It was 17. deg. 30. m. from the Pleiades , or Seven Stars . It was in the 16. degree of Taurus . From December 14 , 1680. until February 8 , 1681. It had advanced , the matter of 120. degrees , in the Arch of a great Circle , following the order of the 12. Signs , from about the beginning of Capricorn , to the 16. of Taurus .

This perhaps , may be lyable to the Pharisaick Censure , of some Mathematical Rabbi ; but let him first , be at as much pains , as I have been at in Observing ; and next , let him make his Observations , as accurate , and true as these are , without an Observatory , and the help , of fit , and proper Instruments .

THese are to give Advertisement , to all Ingenious Persons , who have found out , any New Inventions , or made any New Observations , of things Astronomical , of things in the Sea , in the Earth , above Ground or under . In a word , whatever may be useful , for the promoting of Natural Knowledge , and Learning , and profitable to others , let them be communicated to the Author of this Transaction , a true Narration being made , he shall have them published , with accuracy , and satisfaction to himself .

Printed in the Year ,

PraefVLsêre DVo , res anno rara , pLánetae , HeI nobIs MIserIs , IVngVntVr , In ore LeonIs . When SatVrn In the heaV'ns , to IoVe CoMes near ,

TO THE READER . Courteous Reader ,

I Shall not detain thee in the entry with a long Preface , but give a short account of what is needful to be known , of the Cause , Occasion , and Matter of the following Treatise . After the publication of my last Piece , about the Weight and Pressure of the Air , I found it needful to treat of the Pressure of the Water , because of the near relation between the two : the operations , and effects of both depending almost upon the same Principles and Causes . And that there are many things , which cannot through●y be understood , of the Pressure of the Air , without the knowledge of the Pressure of the Water : therefore to make the first the more evident , I have spoken of the second : the effects and operations of Hydrostatical Experiments , being more conspicuous and sensible , then the effects and operations of the other .

The Occasion was some spare time I had now and then , for making some Trials : part whereof are published here ; the rest being rather some productions of Reason , attentively exercised on that Subject ; which notwithstanding may be called Experiments , though never actually tried , nor haply can be , because of some accidental impediments : yet supposing they were , I make it evident , that such and such Phenomena would follow , whence many necessary conclusions are inferred .

As for the subject matter , there are first , moe then thirty Theorems in order to the Pressure of Fluid Bodies , as Air , Water , and Mercury , which in effect are nothing else , but so many conclusions rationally deduced from various and diverse effects of Aerostatical , Hydrostatical , and Hydrargyrostatical Experiments , which for the most part , I have tried my self .

There are next twenty Experiments briefly described , by their own distinct Schematisms : their Phenomena , according to the Laws of the Hydrostaticks are salved , and several new conclusions inferred . A Proposal is likewise made of a more convenient Engine for Diving . Here , several difficulties are proposed , and answered , and all the obvious Phenomena of Diving explicated . If the Lead which sinks the Ark , be judged too weighty , and big , which may render it not so tractable , and likewise hinder the Ark from going so near to the ground , as is desirable , and in some measure stop the sight , ( which troubles are ( I suppose ) incident to the Bell also ) it may be reduced to a far less weight , and quantity , and the overplus being made square and thin pieces , may line the mouth of the Ark without , between P Q and L M , according to the Figure 25 , or may be put to , or taken away at pleasure . The Bell may have likewise in stead of this troublesome Foot-board , a weighty Ring of Lead , or two , to go round about the orifice without , in form of a Girth , or Belt , which may slip off and on at pleasure , and will as conveniently sink it , as if it had a weight appended : the Foot-board then may be of any form , quantity , or weight you please .

There are thirdly some Miscellany Observations , the design of which is only Philosophical . Some of them are Experiments made with the Air-pump , which I have adventured to insert here , even though the Noble Mr. Boyl hath given an account of many . But because the Engine was offered to me by the Laird of Salton , a Gentleman of a choise Spirit , I could not , but in obedience to his commands make use of it , and shew him the Product . There are also two or three observations in the close , as that of the Primum vivens in Animals : of the Aliment , and growth of plants : and of the motion of the Aliment in Trees . To all which is added a short History of Coal , which I hope will be acceptable to some ; this so needful a subject , never being treated of before by any . In it , mention is made of things common to Coal in general , as Dipps , Risings , and Streeks . Next , of Gaes , or Dykes , which prove so troublesome sometimes to the working of Coal . Thirdly , of Damps , and Wild-fire . Next , a method is taught for trying of Grounds , where never any Coal was discovered before . And lastly , the manner how Levels , or Conduits under-ground , ought to be carried on , for draining the Coal , and freeing it of Water .

When this Book was first committed to the Press , I sent an intimation thereof to some of my friends , for their encouragment to it , a Practice now common , and commendable , which hath not wanted a considerable success , as witness the respect of many worthy persons , to whom I am oblidged . But there is a Generation , that rather , than they will encourage any new Invention , set themselves by all means to detract from it , and the Authors of it : so grieved are they , that ought of this kind should fall into the hands of any , but their own . And therefore , if the Author shall give but the title of New to his Invention , though never so deservedly , they fly presently in his throat , like so many Wild Catts , studying either to Ridicule his work altogether ▪ a trade that usually , the person of weakest abilities , and most empty heads , are better at , than learned men , like those Schollars , who being nimble in putting tricks , and impostures upon their Condisciples , were dolts , as to their Lesson , or else fall upon it with such snarling , and carping , as discover , neither ingenuity , nor ingeniousness , but a sore sickness , called Envy .

In the Intimation , I affirmed , that the Doctrine concerning the Weight , and Pressure of the Water was New . This one word , like a spark of Fire falling accidentally among Powder , hath been the occasion of so much debate . Their ground is , because they look upon the Hydrostaticks , as a Science long ago perfected , seing Archimedes 2000 years ago hath demonstrat the Water to have a Pressure , and some others since , as Stevinus . They affirm likewise , that all the Theorems , and Experiments , that are here , are either deduceable from Archimedes , and Stevinus , or are the same with theirs . If these Gentlemen had suspended their judgment , till this Book had been published , I suspect they would not have spoken so confidently . For Archimedes his propositions , they are but few , and proven ( as Mr Boyl saith ) by no very easie demonstrations , which have more of Geometrical subtility , than usefulness in them . But these , which are here proposed , are not only useful , but evidently evicted by reason , and sensible Experiments , even to the meanest capacities . And though some of mine , may ( perhaps ) co-incide with some of his , which to me is but accidental , yet our way of procedour is toto Coelo different . His way is more Speculative : this is more Practical . His demonstrations are Geometrical : these are Physical . His propositions are but for the use of a few : these are for the use of all . His are not illustrated , and confirmed by Hydrostatical Experiments : these are .

Stevinus a late Writer keeps that same method . Yet I judge it easie to let see , even in the entry , how little cogent some of his demonstrations are , without derogating from such a Learned Man . He hath indeed some Pragmatical Examples ( as he calls them ) for illustrating some of his Geometrical Propositions , anent the Pressure of the Water ; but I leave them to be considered by the judicious and understanding . Again , in this Method , I am yet as much different from others , who have written lately , as from these I have been speaking of . For , I not only treat of the Pressure of the Water , but takes in with it , the Pressure of the Air joyntly ; since to explicat sufficiently the Phenomena of the Hydrostaticks , without it , it is impossible . And yet furder , I not only counterpoise Air with Water , but Air with Mercury , and Water with Mercury ▪ by which means several mysteries , and secrets in this Art , are discovered .

There are several Inventions found out of late in the Hydrostaticks , whose ●●ents and effects , cannot be clearly deduced from the grounds of Archimedes , and Stevinus , who had not that clear discovery ( for ought we know ) of the Pressure of the Air , that some now have , without which , these effects can never be sufficiently explained . And who doubts , but others afterwards , may make farder discoveries , and profit the world yet more , with their Inventions , then any have yet done . Is then the Hydrostaticks , a Science long ago perfected ? To this Pedantick Conceit , I must again oppose the judgment of Mr. Boyl , who saith moreover , that the usefulness of this part of Philosophy hath been scarce known any farder than by name , even to the generality of learned men .

But let us suppose that the notion of the Pressure of the Water , is of an old date , even as old as the Flood ( for Noah surely knew , that the Pressure of the Water , would sustain the Ark ) and ( giving , but not granting ) that Archimedes 2000 years ago hath written all the Principles of the Hydrostaticks , doth this hinder any man now , from deducing new Conclusions from these old Principles ? But there is here , no such thing for neither in this , nor in my last Piece , are my Adversaries able to trace me . 'T is like the purposes would have been so much the better , if I had followed other mens foot steps : and it is like they might have been so much the worse . I doubt not , but I have lighted upon other mens thoughts in some things : and others writting on this same subject , who perhaps are my Antipodes , may fall upon mine . My Antagonists affirm , they are able to deduce all my Theorems , and the events of all my Experiments from the grounds of Archimedes and Stevinus . If they take not their word again , I hope they will do it ; for now I put them to it . And though they should , ( which I am not affraid they shall do in haste ) yet they must prove next , that these Theorems and Conclusions , so deduced , are not new , which all their Logick will not prove . But what if we do more , ( say they ) even overthrow many of all your Aerostatical and Hydrostatical Experiments , in this , and in your last Pe●ce ? I give you liberty , and for your hire , a Guiny for each Theorem , or Experiment , you are able to ransack , in either of the two Books , though they come near to an hundred . But , ye must oblige your selves ( my Maste●s ) to do it with Reason , laying aside your Sophistry and ●anina eloquentia . And this I offer , Reader , that I may reduce them , to a better humour , and encourage them to leave off flyting , and only use reason . Neither must they be like the Wasp , that only lights upon the sore place . But if they love to kindle any more fire , they will find me proof against it . If it burn them , it shall not heat me . Nevertheless , if they love to juik under deck , like Green-horns , having no courage in themselves , or confidence in their cause , they must excuse me , if at last , I write their names upon a Ticket , and bring them above deck . This is all I have to say , at present ( Reader ) and I bid thee farewell .

ERRATA .

Pag. 21. lin. 8. for weight read bensil . Pag. 185. lin. 24. for EH , read FH . Pag. ●35 . lin. 24. for 500. read 5000. Pag. 307. lin. 26. read promoting . Pag. 313. lin. 22. read reflection . Ibid. lin. 25. read elaborarint . Pag. 317. lin. 2. read & magna .

Note , that in placing the Figures , the 12 , that should have the fourth place in the third Plate , hath the first place in the fourth .

Contents of the EXPERIMENTS . THe first , second , and third Experiment , touching the rising and falling down of Water in Tubs of different sizes . Pag. 37.41.44 . The fourth is a Hydrostatical Experiment , shewing the Reason why the Mercurial Cylinder rises , and falls , in the Torricellian Experiment , as it is carried up , or down thorow the Air. pag. 46.50 The fifth , shewing the reason , why the Mercurial Cylinder rises and falls in the Baroscope , as the Pipe is reclined and erected . p. 51 The sixth , touching the suspension of Liquors in Pipes , either closs or open above , not only of Water by Water , but of Water by Air. pag. 55 , &c. The seventh , touching the Cause of the suspension , and keeping up of Water in Weather-glasses . pag. 59. The eighth , touching the reason , why a Stone weighs less in Water than in Air. pag. 71. &c. The ninth , touching the reason , why under a Water 34 foot deep , the hight of the Mercury in the Baroscope , is 58 inches . pag. 77. &c. The tenth , touching the reason , why a man gripping with his fingers the Torricellian Tub , seems to find the weight of the Liquor within , and yet finds it not . pag. 82. &c. The eleventh , touching the counterpoising of Mercury in Glass-pipes under-water , by the help of a Ballance above , adduced to prove that a heavy Body weighs as much in Water , as in Air. pag. 86. The difficulty answered , pag. 87. &c. The twelfth , touching the reason , why a Cylinder of Brass , may be suspended by a Surface of Water , before it touch the bottom , that 's 100 foot deep . pag. 101. &c. The thirteenth is , touching two plain heavy Bodies suspended under a Water 34 foot deep . pag. 109 Doctor Mores Argument against the Pressure of the Air , answered . pag. 117 The fourteenth , touching the counterpoising of Mercury with Water : of Mercury with Air and Water ; whence some notable Phenomena appear . pag. 120. &c. The fifteenth , touching an Experiment tried in a Water 72 foot deep . pag. 127. &c. The sixteenth , touching the reason , why the different wideness of Tubs , makes no alteration in the hight of the Liquors suspended in them . pag. 133. The seventeenth , a notable trial for proving the Pressure of the Water . pag. 137. &c. Mr. Boyls Experiment insufficient . pag. 146. The eighteenth , touching the Diving-Ark . pag. 153. &c. The nineteenth , touching a Siphon made to work under Water with Mercury , by the Pressure thereof , as a Siphon operats with Water , by the Pressure of the Air. p. 180. The last is for demonstrating the precise and just weight of any Pillar of Air , Water , or Mercury . p. 183. &c. Contents of the MISCELLANY OBSERVATIONS . Observation 1. Anent the killing of Animals in Coal sinks , by the power of Damps and Ill Air. pag. 197. Observ. 2. Touching the position of Iupiter , with the Stars of Gemini , Novemb. 24. 1669. p. 201. Observ. 3. For knowing the motion of the Sun , or Moon , in seconds of time . ibid. Observ. 4. Touching an Experiment made on the top of Cheviot . p. 207. Observ. 5. Touching the oval-Figure of the Sun , at his setting . p. 209. Observ. 6. Touching a considerable Thunder , with great Lightnings , in East-Lothian , in Iuly 1670. p. 210. Observ. 7. A method for finding out the true South and North Points . p. 212. Observ. 8. Touching the reason , why a dead body of a man , or beast , riseth from the ground of a Water , after it hath lien there three or four dayes . p. 216. Observ. 9. Is a second Experiment made in a Coal-sink , for knowing the power of Damps and Ill-Air . p. 217. Observ. 10. An account of Experiments tried with the Air-pump . p. 218. Observ. 11. An Experiment made , for knowing the reason , why a round heavy Body , as a Bullet of Iron , falls not off a plain Body , under motion , but lies dead . p. 224. Observ. 12. Shewing the reason why a stone demitted from the top of a Ships-Mast under Sail , falls directly upon the place it hang over . p. 226. Observ. 13. Touching the hight of the Mercury in the Baroscope , observed by D. Beal . p. 228. Observ. 14. Touching the variation of the Magnetick Needle here . p. 228. Observ. 15. Touching the Elevation of the Pole here . p. 228. Observ. 16. A second method for finding the Meridian . p. 229. Observ. 17. Touching a considerable showre of Hail , with Thunder , and Rain . ibid. Observ. 18. Touching a curious Experiment made lately in Germany , for shewing the wonderful force of the Air. p. 230. Observ. 19. Touching some proposals of new Engines for War . p. 233. Observ. 20. Touching a sad trial one Mr. Campbel suffered in his Family for many dayes from the Devil . p. 238. Observ. 21. Touching a large Horn cut off a Womans head lately . p. 248. Observ. 22. Touching the Primum vivens in Animals . ibid. Observ 23. Touching the Aliment and growth of Plants p. 252. And touching the motion of the aliment in Trees . p. 254. Observ. 24. Touching a History of Coal . p. 258.

In Auctorem & Opus ENCOMIASTICON . AETher is expansi , vitrei Maris Antitalanton , Peroledos , Elasin , Fluidarum ritè videntes , Ingenio patefacta tuo , Magnalia rerum , Laudarûnt alacres Galli , Belgaeque sagaces . Aggreder is nunc Arte Novâ , trutinare profundi Corpora , submersas quondam producere Gazas , Tollere demersis ingentia pondera Cupis . Gas fracidum in Cryptis ortum Fossoribus atrox , Submisso in Fundos Aurae renovante Flabello , Propulsare doces , Lithanthracumque Cavernae Quê is foveantur Aquis , quo tendant , unde oriantur , Ordine quò circum Saxorum strata recumbant . Quòd benè coepisti Naturae cuncta foventis Munera solerti perge Illustrare Mathesi . GEORGIUS HEPBURNUS , M. D. à Monachagro .

To the Reader . Reader ,

That thou mayest know , by one word more , how useful this part of Philosophy is , and how far from being a Science long ago perfected , take but this following proposal , lately , since my Book came to a close , communicated to me by a Friend , which , by his ●llow●nce , I have published , reserving the Answer to himself , the Author thereof .

Brother ,

BY what you have published in your Ars Nova & Magna , and this Book , I have been led to this Invention , to beget within the Bowels of the Sea , a Power , or Force , which with great safety , and ease , shall bring up the greatest weight , that can be sunk therein : ad data quae cunque pondera demersa , in Maris visceribus Potentiam producere , quae modo securo , & facili , è fundo cujusvis altitudin's ad summum , ipsa evehat . I drew a Letter one night , sh●wing the way how this might be done , which I communicated to you , that it might have been Printed with your Book : but after second thoughts , I judged it more meet to keep it up for a time , and that it should be set forth by way of Proposal only at the first , by

Your Brother , Mr. Iohn Sinclar . O miston , May 20. 1682.

This New Invention , though Hydrostatical , is tru●y Mechanical , there being here a ●ondus and a Potentia , whose operations depends upon Mechanical Principles . But in several respects it is far more admirable , than the most part of the Mechanical Engines , which are look'd upon as stupendious . Many things , almost incredible , are reported of Archimedes , which he admirably brought about , by his Mechanical Powers ; but I am confident , that by this Invention , as great a weight may be lifted , if not greater , as the Power of any Mechanical Faculty can be able to move . I know , the greatest conceivable weight , may be demonstrat , to be moved by the least conceivable Power , as the Earth , by the force of a mans hand . But how is it possible to contrive Artificially , an Engine for that purpose , which will do that by Art , which the demonstration makes evident by reason ? It was thought a great enterprize , when Pope Sixtus the fifth , transported an Obelisk , which had been long since dedicated to the memory of Iulius Cesar , from the left side of the Vatican , to a more eminent place , 100 foot distant ; but to raise a Ship of 1000 Tun intirely , nay , a weight 100 times greater , is surely a far greater enterprize . This Invention is so much the more admirable , that not only by it , any supposed weight may be lifted , but from any deepness . Though this ( perhaps ) cannot be done Mechanically , because of some Physical , or Moral impediment , yet according to the Laws of the Hydrostaticks it can be demonstrat , and made evident by reason . And if this be , then surely , when the Weight is determinat , as the burdens of all Ships are , and the deepness known to be within so many fathoms , this Invention cannot but be successful .

Though the strength of Mechanical Inventions , may be multiplied , beyond the bounds of our Imagination , whereby the greatest Weight , may be moved , by the least Power ; yet the Wisdom of God , hath thought it fit , so to confine that knowledge , that it cannot teach , how both of them , can move with the same quickness and speed . For , if that were , the very works of Nature might be overturned . Therefore , it is observable , that when a great Weight is moved by a small Power , the motion of the one , is as much slower than the motion of the other , as the Weight of the one , exceeds the Force of the other . If it were possible Mechanically to move the Earth with the Force of a mans hand , the motion thereof would be as much slower , than the motion of the hand , as the Weight of the one , exceeds the Force of the other , which is a great disadvantage . And as the Weight and Power do thus differ , as to swiftness , and slowness in motion , so also , as to Space . For , by how much the Power is in it self less , than the Weight , by so much will the bounds or Space , the Weight moves thorow , be less than the Space , the Power goes thorow . If it were possible ( keeping the same instance ) to move the Earth with a mans hand , the Space thorow which it passeth , would differ as much from the Space the hand goes thorow , as the one exceeds the other ; which is another disadvantage .

It may be thought , that if this Invention depend upon Mechanical Principles , it may be obnoxious to these abatements . I answer , though there be in it a Pondus , and a Potentia , a Weight , and a Power , this moving the other , yet it will evidently appear from Experience , that the motion of the one , is as swift as the motion of the other , and that the one moves as much Space and bounds in the same time , as the other , which is a great advantage . In this , it excells all the Mechanical Powers , and Faculties , that have ever yet been invented and practised . If any think , that such a device cannot be effectuat , without a considerable expence . I answer , the expence is so small , that I am ashamed to mention it . The method and manner of doing this , is most easie likewise . Neither ought this to be a ground , why any man should contemn it ; since the most useful Inventions ordinarily are performed with the greatest facility .

As it commends this part of Philosophy to all ingenious Spirits , as most pleasant , and most profitable , so it gives a check to the ignorant , who look upon it as a Science long ago perfected .

In praise of the AUTHOR , and his WORK . 1. WHilst Infant-Art no further did pretend Then to flat notions , and a bare desi●e ; What by small toyl we now do comprehend , Our Predecessors only did admire . 2. Now fruitful Reason , arm'd with powerful Art , Uncovers Nature to each knowing eye : Our Author to the World doth here impart What was before esteem'd a mystery . 3. The various motions of that Element , Whose liquid form gives birth to much debate ; By demonstration he doth represent , Unfolding th' intrigues of that subtil state . 4. The Waters Course , and Sourse , from whence they flow , By him to th' sense so clearly are display'd ▪ Their current Weight , and Measure now we know , 'T is no more secret , but an open Trade . W. C.

Hydrostatical THEOREMS , Containing some useful Principles in order to that excellent Doctrine , anent the wonderful Weight , Force , and Pressure of the Water in its own Element .

THEOREM I. In all Fluids , besides the first and visible Horizontal surface , there are many moe imaginary , yet real . Figure 1.

FOR the better understanding the following Experiments , it is needful to premit the subsequent Theorems ; the first whereof is , that in all Fluid bodies , such as Air , Water , and Mercury , or any other liquid , there is besides the first and visible surface , innumerable moe imaginary , under that first , yet real , as may be seen from the following Schematism , which represents a Vessel full of Water , where besides the first surface ABCD , there is a second EFGH , and a third IKLM , and so downward , till you come to the bottom . This holds true , not only in Water , but in Air also , or in any other Fluid body whatsoever . I call the under-surfaces imaginary , not because they are not real ; for true and real effects are performed by them ; but because they are not actually distinguished amongst themselves , but only by the Intellect .

THEOREM II. In all Fluids , as it is needful to conceive Horizontal Plains , so it is needful to conceive Perpendicular Pillars , cutting these Plains at right Angles . Figure 1.

THis Proposition is likewise needful for understanding the following Doctrine , anent the Pressure of the Water : for in it , as in all Fluids , though there be not Columes or Pillars actually divided , reaching from the top to the bottom , yet there are innumerable imaginary , which do as really produce effects by their pressure , as if they were actually distinguished . These imaginary Pillars are represented in the first Schematism , one whereof is AEINOPQ , the other BFKRT , and so forth .

THEOREM III. There is a twofold Ballance , one Natural , another Artificial .

BY the Artificial Ballance , I understand that which the Mechanicks call Libra , which Merchants commonly use . By the Natural Ballance ( which for distinctions cause I so nominat ) I mean , v. g. a Siphon , or crooked Pipe , wherein water naturally ascends or descends , as high or low in the one Leg , as in the other , still keeping an evenness , or likeness of weight .

THEOREM IV. Fluid bodies counterpoise one another in the Ballance of Nature , according to their Altitude only .

THis Theorem will appear afterwards most evident , while we pass through the several Experiments ; and it is of special use for explicating sundry difficulties that commonly occur in the Hydrostaticks . The meaning of it is shortly this : while two Cylinders of Water are in the opposite Scales of the Natural Ballance , they do not counter poise one another according to their thickness : for though the one Pillar of Water be ten times thicker , then the other , and consequently heavier , yet is it not able to press up the other , that 's more slender , and so lighter , beyond its own hight : and therefore they weigh only according to their Altitudes .

THEOREM V. In all Fluids there is a Pressure . Figure 1.

THis is true not only of the Elements of Air , and Water , while they are out of their own place ( as they speak ) but while they are in it . For Air and Water , being naturally indued with weight , the second foot cannot be under the first , unless it sustain it : if this be , it must necessarily be prest with its burden . So this Water being naturally a heavy body , the foot I cannot be under E , unless it sustain it , and be prest with the burden of it ; the foot N , being burdened with them both . From this Pressure , which is in Air , ariseth a certain sort of force , and power , which may be called Bensil , by vertue whereof , a little quantity of Air , can expand and spread out it self , to a very large quantity , and may by extrinsick force be reduced to that small quantity again . Though this expansive faculty be evident in Air , yet it is scarcely discernable in Water , unless it be in very deep parts , near the bottom , where the Pressure is great . This Pressure is not of the same Degree in all the parts , but is increased and augmented , according to the deepness of the Air and Water ▪ for the Air upon the tops of Mountains , and high places , is thought to be of a less Pressure , then in Valleys : and Water is of a less Pressure , ten or twelve foot from the top , then twenty or thirty . So is the Water N , under a far less Pressure , then the Water , P or Q.

THEOREM VI. The pressure of Fluids is on every side . Figure 1.

THe meaning is , that Air and Water presseth not only downward , but upward , not to the right hand only , but to the left also , and every way . So the foot of water K , not only presseth down the foot R , but presseth up the foot F , yea presseth the foot I , and the foot L , with the same weight . And the first imaginary surface , is as much prest up , by the water IKLM , as it is prest down by the water EFGH . Upon this account it is , that when a Sphere , or Glob is suspended in the midle of Water , or Air , all the points of their surfaces are uniformly prest . After this manner , are our bodies prest with the invironing Air , and the man that dives , with the ambient and invironing Water .

THEOREM VII . All the parts of a Fluid in the same Horizontal Line , are equally prest . Figure I.

THe meaning is , that the foot I , is no more prest , then the foot K : neither is the foot L , more burdened , then the foot M. The reason is , because each of these feet , sustains the same weight : for EFGH are all of them , of the same burden : therefore all the parts of a Fluid in the same Horizontal surface , are prest most equally . This holds true in Air , and Mercury , or in any other Liquid also .

THEOREM VIII . The Pressure of Fluids seem to be according to Arithmetical Progression . Figure I.

THe meaning is , that if the first foot of Water , have one Degree of Pressure in it , the second must have only two , and the third must have only three , and so forth , which appears from the Schematism : for the first foot E , having one Degree of weight , and the second foot I , having of its self as much , and sustaining E , it must have two Degrees , and no more . So the foot N , sustaining two Degrees of Pressure from I and E , must have the weight only of three Degrees , O of four , P of five . It 's evident also from Experience , for while by the Pressure of Water , Mercury is suspended in a glass tub , we find , that as the first fourteen inches of Water , sustains one inch of Mercury , so the second fourteen inches sustains but two , and the third , but three . But if the Pressure were according to Geometrical progression , the third foot of Water ought to sustain four inches of Mercury , the fourth , eight ; the fifth , sixteen , &c. which is contrary to Experience .

THEOREM IX . In all Fluids there is a twofold weight , one Sensible , the other Insensible .

THe first is common to all heavy bodies , which we find in Water , while we lift a Vessel full of it from the ground . The Insensible weight of Water , and Air , or of any other Fluid , can scarcely be discerned by the senses , though it be as real , as the former , because the Pressure is uniform . By vertue of the second , bodies naturally lighter than Water , are driven from the bottom to the top , as Cork . So , a man falling into a deep Water , goes presently to the bottom , and instantly comes up again . Here is a natural effect , which cannot want a natural cause ; and this can be nothing else , but the Pressure of the Water , by vertue whereof he comes up , and yet he finds nothing driving him up , or pulling him up . Therefore , there is in all Fluid bodies , an Insensible weight , as there is one Sensible ; seing the man that ( perhaps ) weighs seventeen Stone , is driven up fifteen or sixteen fathom by it . And it must be very considerable , and exceed the weight of the man , seing it is able to overcome such a weight . So are vapours and smoke driven upward by the Insensible weight of the Air , and by that same weight , do the Clouds swim above us .

THEOREM X. The Insensible weight of Fluids , is only found by sense , when the Pressure is not uniform .

FOr understanding of this Proposition , I must suppose somethings that are possible , but not practicable . Put the case then , while a man opens his hand , the Air below were removed , he would scarce be able to sustain the weight of the Air , that rests upon the Palm above : or if the Air above were annihilated , he would not be able to bear down the weight that presseth upward . Or , while a Diver is in the bottom of the Sea , if it were possible to free any one part of his body from the Pressure of the Water , suppose his right arm , I doubt not , but the blood would spring out in abundance from his finger-ends : for the arm being free , and the other parts extreamly prest , the blood of necessity must be driven from the shoulder downward , with force , which cannot be without considerable pain . It is evident also , from the application of the Cuppin-glass , which being duely applied to a mans skin , causeth the Air to press unequally , the parts without , being more prest than the parts within , in which case the unequal Pressure causeth the pain , and so is found by sense .

THEOREM XI . A Cylinder of Water , or of any other Fluid body , loseth of its weight , according to its reclination from a Perpendicular position , towards an Horizontal or levell scituation .

FOr understanding of this , consider that while a Pipe full of Water stands perpendicular , the lowest foot sustains the whole weight of the Water above it : but no sooner you begin to recline the Pipe from that Position , but assoon the Pressure upon the lowest foot grows less ; So that if the lowest foot , in a perpendicular position , sustained the burden of ten feet , it cannot sustain above five or six , when it is half reclined . A certain evidence whereof is this , the more a Cylinder of Water is reclined towards the Horizon , or Level , it takes the shorter Cylinder of Water to counterpoise it , as is evident in Siphons . For , though the one Leg , be sixteen inches long , and the other but six ; yet a Cylinder of Water six inches long , will counterpoise a Cylinder of sixteen . But this cannot be , unless an alteration be made in the Pressure . For , how is it possible , that a Cylinder of Water can sometimes be in aequilibrio with a lesser , and sometimes with a greater weight , unless the Weight , and Pressure of it , be sometimes more , and sometimes less ? When I say a Cylinder of Water loseth of its weight by reclination , it is to be understood only of the Insensible Weight : for the Sensible Weight is unchangeable , seing it is alwayes a Pillar of so many inches , or feet . Now the true reason , why the Pressure upon the lowest foot grows less , is this ; the more the Pipe is reclined , the more weight of the Cylinder rests upon the sides of the Pipe within ; by which means , the lowest foot is eased of the burthen , and is altogether eased , when once the Pipe lyes Horizontal .

THEOREM XII . All motion in Fluids , is from the unequal Pressure of the Horizontal surface . Figure 1.

FOr understanding this , I must distinguish a twofold motion in Fluids ; one common , another proper , by vertue of the first , they incline , as all other heavy bodies , to be at the center of the Earth . It is evident in the motion of Rivers , which descend from the higher places to the valleys , even by vertue of that tendency they have to be at the center . By vertue of the second , they incline to move every way ; not only downward , but upward , hither and thither . This sort of motion is peculiar , and proper only to Fluids ; and it is that which is spoken of in this Theorem . I say then , that all motion in Fluids , is from the unequal Pressure of the Horizontal surface . For put the case A , were more prest then B , e. g. with a stone , then surely as the part A descends , the other part B will ascend , and so will C and D rise higher too . Suppose next , the part A were fred of the Pressure of the Air , then surely in the same instant of time , would the part A ascend , and the parts BCD descend . As this Proposition is true in order to the first and visible surface ABCD , so it is true in order to the imaginary surface IKLM ; for put the case the space I , were filled with a body naturally heavier then Water , as lead or stone , then behoved that part of the surface to yeeld , it being more prest , then the part of the same surface K. Or if the space K were filled with a body naturally lighter then water , as Cork , then ought the water R to ascend , it being less prest , then the water N or S.

THEOREM XIII . A body naturally heavier then Water , descends ; and a body naturally lighter , ascends . Figure 1.

FOr understanding of this , let us suppose the quadrat space E , to be filled with a piece of Lead or Iron . I say then it must go down to I ; and the reason is , because the quadrat foot of Water I , is more pressed then the quadrat foot of Water K. To illustrat this , let us suppose that each quadrat foot of this Water weighs a pound , and that the heavy body existing in E , weighs two pound . If this be , the foot of Water I , must yeeld , seeing it is more prest then K : upon the same account must the Water N yeeld , and give way to the Stone , seeing it is more prest then R. For according to the twelfth Theorem , There cannot be unequal Pressure upon a surface , unless motion follow .

For understanding the second part , let us suppose the space R , to be filled with a piece of Cork , that is specifically or naturally lighter then Water . I say then , it must ascend to the top B ; and the reason is , because the quadrat foot of Water K , is more prest upward , then the quadrat foot of Water I , or L is : but this cannot be in Fluid bodies , unless motion follow thereupon . I say , it is more prest up , because R being lighter then N , or S , it must press with greater force upon K , then S can do upon L , or N upon I. It is still to be remembred , That Fluids presseth with as much strength upward , as downward , according to the sixth Theorem ; and that an Horizontal surface doth as really suffer unequal Pressure from below , as from above .

THEOREM XIV . Bodies naturally lighter then Water , swim upon the surface and top . Figure 1.

THe reason of this Proposition must be taken from the nature of an equipondium , or equal weight . For without doubt , there is a counter-ballance between the Pressure of the Water , and the weight of the body that swims . To make this probable , let us suppose there were a piece of Timber in form of a Cube , six inches thick every way , without weight . In this case , the under-surface of that four-squar'd body , being applied to the surface of the Water A , would ly closs upon it , as one plain Table lyes upon the face of another , without any pressure : and it being void of weight , the part of the surface A , would be no more burdened , then the next part B adjacent , whence no motion would follow . Here is no equipondium , or counter-ballance .

Secondly , let us suppose the said body to acquire two ounces of weight , then it follows , that it must subside , and sink two inches below the surface ABCD ; and that so far , till it come by vertue of its new acquired weight , to a counter-ballance with the Pressure of the Water . Which Pressure is nothing else , but as much force or weight , as is equivalent to the weight of Water , that is thrust out of its own place , by the subsiding and sinking of that body , two inches .

Thirdly , let us suppose the same body to acquire other two ounces of weight , then must it subside other two inches . Lastly , let us suppose that it acquires six ounces of weight , then it follows that the whole body sinks , so far , I mean , till its upmost surface be in an Horizontal line with the surface of the Water ABCD. Here it swims also , because the weight of it becomes just the weight of so much Water , as it hath put out of its own place . I say , it must swim , because if the Water I , was able to sustain the Water E , which is put from its own place , surely it must be able to sustain that body also , that did thrust it from its own place , seing both are of the same weight , namely six ounces . In this case , the body immerged , and the water wherein it is drowned , become of the same weight specifically , seing bulk for bulk is of the same weight . To make this body specifically , or naturally heavier then Water , and consequently to sink to the bottom , nothing is required , but to suppose that it acquires one ounce more of weight ; which done , it presently goes down , I , being more burdened then K. Note by the way , a twofold weight in heavy bodies , one individual , the other specifick , and that two bodies agreeing in individual weight , may differ in specifick weight . So a pound of Lead , and a pound of Cork , agree individually , because they are both 16. ounces : but they differ specifically , because the one is naturally heavier then the other .

THEOREM XV. No Body that flots above Water , even though its upper surface be level with the surface of the Water , can ever be made to swim between the top and the bottom . Figure 1.

FOr clearing this Proposition , let us suppose F to be a four-square piece of Timber , of the same specifick and natural weight with Water , and consequently its upper surface to be level with the surface of the Water ABCD. I say then , if it be prest down to R , it shall arise thence , and never rest till it be where it was , namely in F. The reason seems to be this , because the four-squar'd body of Water R , is really heavier , then the four-squar'd piece of Timber F. If this be true , it follows of necessity , that it must ascend : for if the Timber existing in R , be lighter then the Water R , the Water T must be less prest , then the Water O , or the Water V ; whence ( according to the twelfth Theorem ) motion must follow . Again , if the Timber R , existing in the Water R , be lighter then the same Water is , then must the Water K , be more prest up then the Water I , or L ; whence yet , according to the same Theorem , motion must follow . If it be said , that the Timber F , is of the same weight with the Water R , because , it being equal in weight with the Water F , which it hath thrust out of its own place , it must also be equal in weight to the Water R , seeing F and R being of the same dimensions , are of the same weight . There is no way to answer this difficulty , unless I say the four-squar'd body of water R , is really and truly heavier then the four-squar'd body of Water F. The reason seems to be , because the Water R , is under a greater Pressure , then the Water F ; and by vertue of this greater Pressure , there are really moe parts of Water in it , then in F ; therefore it must be heavier . Even as there are far moe parts of Air , in one cubick foot near the Earth , then in six or seven near the Atmosphere . Hence it is , that a pint of Water taken from the bottom of the Sea , fourty fathom deep , will be heavier , I mean in a ballance , then a pint taken from the surface . Take notice , that when the vessel is once full at the bottom , the orifice must be closely stopped , till it come to the top : otherwise the parts that are compressed at the bottom , namely by the weight of the superiour parts , relaxes themselves , before they come to the top .

THEOREM XVI . It is not impossible for a body to be suspended between the surface and the bottom . Figure 1.

FOr understanding this , suppose F to be a four-square piece of Timber , which though it will not rest but at the surface , ABCD , yet may be made to go down of its own accord , and rest at T , namely , by making it so much heavier , as the Water T is heavier then the Water F. To know this difference , which is not very practicable ; the Cube of Water T , must be brought from its own place , under the same degree of Pressure it hath , and put into the Scale of a Ballance , and weighed with the Cube of Water F , put into the other Scale . Now if the Water T , be half an ounce heavier , then the Water F , then to make the Timber F hing in T , it must be made half an ounce heavier . There seems to be reason for it also ; for if a Cube of Timber resting in the space T , be just the weight of the Water T , the imaginary surface OTV , is no more prest , then if T were Water , and so it cannot go downward : neither can it go upward , seing the under part of the Water R , is no more prest up by the Timber T , then if the space T were filled with Water . If it be said , according to this reasoning , a Stone may be suspended in a deep Water , between the top and the bottom , which is absurd . I answer , such a thing may happen in a very deep Water : For put the case a Cube of Lead twelve inches every way , were to go down twelve thousand fathom , it is probable , it would be suspended before it came to the ground . For coming to an imaginary surface far down , where the Pressure is great , a Cube of Water twelve inches thick there , may be as heavy ( even specifically ) as the Cube of Lead is , though the Lead be ten times heavier specifically , then any foot of Water at the top . If Water suffer compression of parts , by the superiour burden ; it is more then probable , that the second foot of Water burdened with the first , hath moe parts in it , then are in the first , and the third moe , then in the second , and so forth ; and consequently , that the second is heavier , then the first , and the third heavier , then the second . Now , if this be , why may not that foot of Water , that hath sixty thousand foot above it , by vertue of this burden , be so comprest , that in it may be as many parts , as may counter-ballance a Cube of Lead twelve inches every way ? If then , that imaginary surface , that is sixty thousand foot deep , be able to sustain the said foot of Water , which perhaps weighs twenty pound , why may it not likewise sustain the Lead , that is both of the same dimensions with it , and weight ? Hence it is , that the Clouds do swim in the Air , by vertue of a counter-ballance : And we see , which confirms this Doctrine , that the thinnest and lightest are alwayes farthest up ; and the thickest and blackest , are alwayes farthest down .

THEOREM XVII . The lower the parts of a Fluid are , they are the heavier , though all of them be of equal quantity and dimensions . Figure 1.

THis follows from the former , which may appear a Paradox , yet it seems to be true : for though the Water Q at the bottom , be of the same dimensions with the Water E at the top , yet it is really heavier , which happens ( as I said ) from the superiour Pressure . It is clear also from this , namely the Cube of Timber E , which swims upon the surface , being thrust down to Q , comes up to the top again , which could not be , unless the Water Q , were heavier then the Water E. I suppose the Water E , and the Timber E , to be exactly of the same sp●cifick weight , and consequently the surface of the Timber , to ly Horizontal with BCD . Now the reason , why the Timber ascends from Q to E , is no other then this , namely that the one Water is heavier then the other ; for the under part of the Water P , being more prest up with the Timber existing in Q , then with the Water Q it self , it must yeeld and give way to the ascent : for if the Cube of Timber existing in Q , were as heavy as the Water Q it self , it would no more press upon P , or endeavour to be up , then the Water Q does .

THEOREM XVIII . A heavy body weighs less in Water , then in Air. Figure 1.

THis is easily proven from experience ; for after you have weighed a stone in the Air , and finds it two pound , and an half , take it , and suspend it by a threed knit to the scale of a ballance ; and let it down into the Water , and you shall find it half a pound lighter . The question then is , why doth it lose half a pound of its weight ? I answer , the stone becomes half a pound lighter , because the surface of Water on which it rests , sustains half a pound of it : For put the case a stone were resting in R , that weighed two pound and an half in the Air , it behoved to weigh but two pound in this Water ; because the Water T sustains half a pound of it . For if this Water T be able to sustain the Water R , that weighs half a pound , it must be also able to sustain half a pound of the stone , seing half a pound of stone is no heavier , then half a pound of Water . Note , that when a heavy body is weighed in Water , it becomes so much lighter exactly , as is the weight of the Water it thrusts out of its own place .

THEOREM XIX . A heavy body weighs less nigh the bottom of the Water , then nigh the top thereof . Figure 1.

FOr clearing this proposition , I must suppose from the 17. Theorem , that the lower the parts of Water be , they are the heavier , though all of them be of equal dimensions . If then the lowest foot Q be heavier , that is , have moe parts in it , then the foot N , it of necessity follows , that a stone suspended in Q , must be lighter then while it is suspended in N or I. Because , if a stone be lighter in Water then in Air , as is said , even by as much , as is the weight of the bulk of Water , that the bulk of the stone expells , then surely it must be lighter in the one , then in the other place ; because suspended in Q , it expells moe parts of Water , then while it is suspended in N or I. For example , let us suppose the Water N , to weigh eight ounces , and the Water Q to weigh nine , then must the stone suspended in Q , weigh less by an ounce , then suspended in N , seeing as much is deduced from the weight of the stone , as is the weight of the Water it expells : but so it is , that it thrusts nine ounces of Water out of its own place in Q , and but eight in N or I ; therefore it must be one ounce lighter in the one place , then in the other . This may be tried , with a nice , and accurat ballance , which will bring us to the knowledge of this , namely how much the foot of Water Q is heavier , then the Water N or O.

THEOREM XX. One part of a Fluid , cannot be under compression , unless all the parts next adjacent , be under the same degree of Pressure . Figure 1.

THis proposition may be proven by many instances : for when the Air of a Wind-gun , is reduced to less quantity by the Rammer , all the parts are most exactly of the same Bensil . So is it in a Bladder full of wind . It 's true , not only in order to this artificial Pressure , but in order to the natural Pressure , and Bensil of the Air likewise . For the Air within a parlour , hath all its parts , under the same degree of natural compression : so is it with the parts of the Air , that are without , and immediatly under the weight of the Atmosphere . It s evident also in the parts of Water : for the foot of Water R , cannot be under Pressure , unless the Water S , and N , be under the same degree of it . Though this be true of Fluids , while all the parts lye in the same Horizontal surface , yet to speak strictly , it will not hold true of the parts scituated under divers surfaces ; for without question , the foot of Water T , must be under four degrees of Pressure , if the Water R , be under three . And if the Air in the lowest story of a building , be under six degrees of Bensil , the Air in the highest story must be under five . If a man would distinguish Metaphysically , and subtilly , he will find a difference of this kind , not only between the first , and second fathom of Air , nearest to the Earth , but between the first , and second foot ; yea , between the first and second inch , and less ; much more in Water , as to sense . However it be , yet the Theorem holds true ; for we find no difference sensible , between the compression of Air in this room ; and the compression of Air in the next room above it , no not with the Baroscope , or Torricellian Experiment , that discerns such differences accurately . I judge it likewise to be true , in order to the next adjacent parts of Fluids of different kinds ; for while a surface of Mercury , is burdened with a Pillar of Water , or a surface of Water , with a Pillar of Air , whatever degree of weight and Pressure , is in the lowest parts of these Pillars , the same is communicated entirely , to the surfaces , that sustains them . So then , there is as much force and power , in the surface of any Water , as there is Weight and Pressure , in the lowest foot of any Pillar of Air , that rests upon it : otherwise , the surface of Water would never be able to support the said Pillar : for a surface of six degrees of force , can never be able to sustain a a Pillar of Air , of eight , or ten degrees of weight .

THEOREM XXI . The Pressure of Fluids , may be as much in the least part , as in the whole . Figure 1.

THis Theorem may seem hard , yet it can be made manifest , by many instances : for albeit the quantity of Air , that fills a Parlour , be little in respect of the whole Element , yet surely , there is as much Pressure in it , as in the whole ; because Experience shews , that the Mercurial Cylinder in the Baroscope , will be as well sustained in a Chamber , as without , and under the whole Atmosphere directly ; which could not be , unless the small portion of Air , that 's in this Parlour , had as much Pressure in it , as in the whole Element . Besides this , it will be found in a far less quantity : for though the Baroscope were inclosed , and imprisoned so closs , within a small Vessel , that the Air within , could have no communion with the Air without , yet the Pressure of that very small quantity , will sustain 29. inches of Mercury , and this will come to pass , even though the whole Element of Air were annihilated . This Proposition is likewise evident in order to the Pressure of the Water : for put the case , the Baroscope , whose Mercurial Cylinder is 29. inches , by the Pressure of the Air ; were sent down to the bottom of a Sea 34. foot deep , within a Vessel , as a Hogs-head , and there exactly inclosed , that the Water within , could have no commerce with the Water without , yet as well , after this shutting up , as before , other 29. inches would be sustained , by the Pressure of this imprisoned Water , which proves evidently , that there is as much Pressure in one Hogs-head full of Water , at the bottom of the Sea , as in the whole Element of Water , above , or about : for an Element of Water never so spacious , if it exceed not 34. foot in deepness , can sustain no more Mercury , then 29. inches by its Pressure . Yea , though the Vessel with the Baroscope , and imprisoned Water in it , were brought above to the free Air , yet will the Water retain the same Pressure , and will de facto sustain 29. inches of Mercury , provided the Vessel be kept closs . It is therefore evident , that as much Pressure may be in one small quantity of Water , as in the whole Element , or Ocean . 'T is to be observed , that this Theorem is to be understood chiefly of the lower parts of Fluids ; seing there cannot be so much Pressure in the Water P , as in the Water Q ; for in effect , there is as much Pressure in the Water Q , as is in the whole Water above it , or about it . From this Theorem , we see evidently , that the Pressure , and Bensil of a Fluid , is not to be measured , according to its bulk , and quantity , seing there is as much Bensil in one foot , nay , in one inch of Air , as is in the whole Element , and as strong a Pressure in one foot of Water , or less , as there is in the whole Ocean : therefore the greatest quantity of Air , hath not alwayes the greatest Bensil , neither the greatest quantity of Water , the greatest Pressure . But this will appear more evident afterwards .

THEOREM XXII . The Pressure , and Bensil of a Fluid , is a thing , really distinct from the natural weight of a Fluid . Figure 1.

THis may be easily conceived ; for as in solid bodies , the Bensil , and natural weight , are two distinct things , so is it in Air , and Water , or in any other Fluid . The weight of a Bow , is one thing , and the natural weight of it , is another . The weight of the Spring of a Watch , and the Bensil of it , are two distinct things . The weight ( perhaps ) will not exceed two ounces : but the Bensil ( may be ) will be equivalent to two pound . Though these may illustrate , yet they do not convince : therefore I shall adduce a reason , and it 's this . The natural weight of a Fluid is less , or more , as the quantity is less or more ▪ but it is not so with the Pressure , because there may be as much Pressure in a small quantity , as in a great , as is evident from the last Theorem , therefore they may be different . The first part of the Argument is manifest , because there is more weight in a gallon of Water , then in a pint . A second reason is , because a Fluid may lose of its pressure , without losing of its weight . This is evident from the Schematism , for if you take away the four foot of Water EFGH , and consequently make the four Pillars shorter , the foot of Water Q becomes of less Pressure , but not of less Weight , seeing the quantity still remains the same : at least , the loss of weight is not comparable , to the loss of Pressure . I say , it becomes of less Pressure , because there is a less burden above it . Thirdly , the Pressure and Bensil may be intended , and made stronger , without any alteration in the weight : so is the Bensil of Air , within a Bladder , made stronger by heat , without any alteration , in the weight of it . Likewise , the Pressure of the foot of Water Q , may be made stronger , by making these four pillars higher , without any alteration , at least considerable , in the weight ; for it still remains a foot of water , whatever be the hight of the pillars above it . Lastly , the weight of a Fluid is essential to it , but the Pressure is only accidental ; because it is only generated , and begotten in the inferiour parts , by the weight of the superiour , which weight may be taken away .

THEOREM XXIII . Though the Bensil of a Fluid , be not the same thing formally with the weight , yet are they the same effectively .

THis proposition is true in order to many other things , besides Fluids : for we see that the Sun , and Fire , are formally different , yet they may be the same effectively ; because the same effects , that are done by the heat of the Sun , may be done by the heat of the Fire . So the same effects , that are produced by the weight of a Fluid , may be done by the Pressure , and Bensill of it . Thus , the Mercurial Cylinder in the Torricellian Experiment , may be either sustained by the Bensil of the Air , or the weight of it . By the Bensil , as when no more Air , is admitted to rest upon the stagnant Mercury , then three or four inches , the rest being secluded , by stopping the orifice of the Vessel . By the weight of it , as when an intire Pillar of Air , from the top of the Atmosphere , rests upon the face of the stagnant Quicksilver . It is also evident in a Clock , which may be made to move , either by a weight of Lead , or by the force , and power of a Steel Spring .

THEOREM XXIV . The surfaces of Waters , are able to sustain any weight whatsoever , provided that weight press equally , and uniformly . Figure 1.

THis is evident , because the imaginary surface of Water OTVX , doth really support the whole sixteen Cubes of Water above it , yea , though they were sixteen thousand , And the reason is , because they press most equally , and uniformly . What I affirm of the imaginary surface , the same I affirm , of the first and visible . For let a plain body of lead , never so heavy , be laid upon the top of the Water ABCD , yet will it support it , and keep it from sinking , provided it press uniformly all the parts of that surface . It is clear also , from the subsequent Theorem .

THEOREM XXV . The surfaces of all Waters whatsoever , support as much weight from the Air , as if they had the weight of thirty four foot of Water above them , or twenty nine inches of Quick-silver pressing them .

THis Proposition is evident from this , that the Pressure of the Air , is able to raise above the surface of any Water , a Pillar of Water thirty four foot high . For , put the case there were a Pump fourty foot high , erected among stagnant Water , and a Sucker in it , for extracting the internal Air , a man will find , that the Water will climb up in it four and thirty foot ; which Phoenomenon could never happen , unless the surface of the stagnant Water , among which the end of the Pump is drowned , were as much prest with the Air , as if it had a burden of Water upon it thirty four foot high . The second part is also evident , because if a man drown the end of a long Pipe , in a Vessel with stagnant Quick-silver , and remove the Air that 's within the Pipe by a Sucker , or more easily by the help of the Air-pump , he will find the Liquor to rise twenty nine inches , above the surface below , which thing could never come to pass , unless the Pressure of the Air , upon the surfaces of all Bodies , were equivalent to the Pressure and weight of twenty nine inches of Quick-silver .

THEOREM XXVI . All Fluid Bodies have a sphere of Activity , to which they are able to press up themselves , or another Fluid , and no further , which is less or more , according to the altitude of that pressing Fluid . Figure 2.

FOr understanding this Proposition , let us imagine GHCD to be a Vessel , in whose bottom , there are five inches of Mercury EFCD . Next , that above the stagnant Mercury , there are thirty four foot of Water resting , namely ABEF . Lastly , that upon the surface of the said Water , there is resting the Element of Air GHAB , whose top GH , I reckon to be about six thousand fathom above AB . Besides these , let us imagine , that there are here three Pipes , open at both ends , the first whereof CAG , having it 's lower orifice C , drowned among the stagnant Mercury EFCD , goeth so high , that the upper orifice goeth above the top of the Air GH . The second , whose lower orifice I , is only drowned among the Water ABEF , reaches to the top of the Air likewise . The third , whose open end K , is above the surface of the Water ANB , and hanging in the open Air , goeth likewise above the Atmosphere . These things being supposed , we see that no Fluid can , by its own proper weight , press any part of it self , higher then it 's own surface , seing the stagnant Mercury EFCD , cannot press it self within the Pipe CG , higher then E. Neither can the Water ABEF , press it self higher within the Pipe IL , then the point N. Lastly , neither can the Air GHAB , press it self within the Pipe KM , higher then M ▪ But when one Fluid presseth upon another , as the Water ABEF , upon the Mercury EFCD , then doth the said Mercury ascend higher than it 's own surface , namely from E to O , which point is the highest , to which the thirty four foot of Water ABEF , can raise the Mercury , which altitude , is twenty nine inches above the surface EIF . But if a second Fluid be super-added , as the whole Air GHAB , then must the Mercury , according to that new Pressure , rise by proportion ; so rises the Mercury from O to P , other twenty nine inches . By this same additional weight of Air , the Water rises thirty four foot in the Pipe IL , namely from N to R. Now , I say , the outmost and highest point , to which the Element of Air GHAB can raise the Mercury , is from O to P ; for by the Pressure of the Water ABEF , it rises from E to O. And the highest point , to which the said Air can raise the Water , is from N to R. The reasons of these determinate altitudes , must be sought for , from the altitudes of the incumbing and pressing Fluids : for as these are less or more , so is the altitude of the Mercury , and of the Water within the Pipes more or less . The hight therefore of the Mercury EO , is twenty nine inches , because the deepness of the pressing water ABEF is thirty four foot . And the hight of the Water NR , is thirty four foot , because the hight of the Air GH , above AB , is six thousand fathom , or thereabout . And for the same reason , is the Mercury OP twenty nine inches .

THEOREM XXVII . A lighter Fluid , is able to press with as great burden , as a heavier . Figure 2.

THis Proposition is true , not only of Water in respect of Mercury , but of Air in respect of them both : for albeit Air be a thousand times lighter then Water , yet may it have as great a Pressure with it , as Water ; as is evident from this second Schematism , where by the Pressure of the outward Air GHAB , twenty nine inches of Mercury OP are supported , as well as the twenty nine inches EO , by the Pressure of the Water ABEF . So doth the same Air , sustain the thirty four foot of Water NR , which are really as heavy , as the twenty nine inches of Mercury OP . Now , if the weight of the Atmosphere , be equivalent to the weight of thirty four foot of Water , or of twenty nine inches of Mercury , 't is no wonder to see Water press with as great weight as Mercury ; which is likewise clear from this same Figure , where by the Pressure of the Water ABEF , twenty nine inches of Mercury EO are suspended , as truly as the Mercury CE , within the lower end of the Pipe , is supported by the outward invironing Mercury . The reasons of these Phenomena , are taken from the altitudes of the pressing Fluids : for though a Body were never so light , yet multiplication of parts makes multiplication of weight ; which multiplication of parts in Fluids , must be according to altitude : for multiplication of parts according to thickness and breadth will not do it . Observe here , that if as much Air , as fills the Tub between N and L , were put into the scale of a Ballance , it would exactly counterpoise the thirty four foot of Water NR , poured into the other scale . Item , that as much Water as will fill the Tub between E and A , is just the weight of the Mercury EO . Lastly , that as much Air as will fill the Pipe , between O and G , is just the weight of the Mercury OP .

THEOREM XXVIII . The Pressure of Fluids , doth not diminish , while you subtract from their thickness , but only , when you subtract from their altitude . Figure 1.

FOr understanding this , let us look upon the first Schematism , where there are four Pillars of Water . Now I say , though you cut off the three Columes of Water , upon the right side , yet there shall remain as much Pressure , in the quadrat foot of Water Q , as was , while these were intire . But if you cut off from the top , the Water EFGH , then presently an alteration follows , not only in the lowest parts , nigh to the bottom , but through all the intermediat parts : for not only the Water Q loseth a degree of its Pressure , but the Waters P and O suffer the same loss . This Theorem holds true likewise in order to the Element of Air. For if by Divine Providence , the Air should become less in Altitude , than it is ; then surely , the Bensil of the ambient Air , that we breath in and out , should be by proportion weakned also . And contrariwise , if the Altitude became more , then stronger should the Bensil be here , with us , in the lowest parts : both which would be hurtful to creatures , that live by breathing . For if the Altitude of the Air , were far more then it is , our bodies would be under a far greater Pressure , which surely would be very hurtful . And upon the other hand , if the Altitude of the Air , were far less then it is , we should be at a greater loss ; for then , by reason of the weak Bensil , we would breath indeed , but with great difficulty .

THEOREM XXIX . A thicker Pillar of a Fluid , is not able to press up a slenderer , unless there be an unequal Pressure . Figure 3.

FOr understanding this , let us suppose this third Schematism to represent a vessel with Water in it , as high as AB , among which is thrust down to the bottom , the Pipe GH , open at both ends . I say then , the two thicker Pillars of Air EA , and FB , pressing upon the surface of the Water AB , are not able to press up the Water HI , or the slender Pillar of Air IG within the Pipe , the one higher then I , the other higher then G. If it be said , they are heavier , because they are thicker . I answer , they are truly heavier , for the Pillar of Air FB apart , will be thrice as heavy , as the slender Pillar of Air IG . But , if you reckon the Pillar of Air EA , upon the left hand , both together , will be six times heavier , then the Air IG : yet are they not able , either severally , or con●unctly , to press up the Water HI , higher then I , or the Air IG , higher then G. For solving this difficulty , I must say conform to the fourth Theorem , that Fluid Bodies , counterpoiseth one another , not according to their thickness , and breadth , but according to their altitude only : therefore , seing the slender Pillar of Air IG , is as high , as either FB , or EA , it cannot be prest up by them . For by vertue of this equal hight , all the three press equally and uniformly , upon the surface of Water AB ; and therefore according to the twelfth Theorem , there can be no motion . But if so be , the Pillar FB , were higher then the Pillar IG , then surely would the Water HI , be prest up ; for in such a case , there is an unequal Pressure . Or if the Pillar IG , were higher then the Pillar FB , then surely would the Water IH be prest down , there being again an unequal Pressure : the Water within the Pipe , being more burdened then the Water about the Pipe . In a word , there 's no more difficulty here , then if the Pipe were taken away : in which case , there would be but one Pillar of Air , resting upon the surface of Water AB . If it be said , the Pipe being thrust down , makes of one Pillar , three distinct ones , and consequently a formal counter-ballance , or mutual sustentation . Be it so , yet because all these press uniformly , there can be no motion .

THEOREM XXX . Fluids press not only according to perpendicular Lines , but according to crooked Lines . Figure 4.

FOr proving this Proposition , let us suppose ABCD , to be a large Vessel full of Water , as high as ANB , and a little Vessel lying within it , near to the bottom , closs above at M , but with an open orifice downward , as G , and having other two passages going in to it , upon the right , and left side , as EO , and FP . Now , I say , the Pressure of this Water , is not only from N to M , in a Straight line downwards , but from E to O , and from F to P , by crooked lines . Nay , put the case this Vessel had no passage in to it , but by a Labyrinth , or entry full of intricate windings , yet the Pressure will be communicated , thorow all these , even to the middle of it : and which is more , the Water H or I , within the Vessel , would be under the same degree of Pressure , with the Water E or L , without , or with the Water K or F. And which is strange , let us suppose both the entries E and F stopped , and nothing remaining open , but the hole G , which I judge no wider , then may admit the hair of ones head ▪ yet thorow that smal hole , shall the Pressure be communicated , to the parts of the Water within , in as high a degree , as if the upper part of the Vessel EML , were cut off , to let the Pressure come down directly . What is true

Fig. 1. Pag. ●

Fig. 2. Pag. 25

Fig. 3 Pag. 29

Fig. 4 Pag. 3● in order to Water , the same is true in order to Air , or Mercury , or any other Fluid . For , though a house were built never so closs , without door , or window , yet if there remain but one smal hole in it , the Pressure of the whole Atmosphere , shall be transmitted thorow that entrie , and shall reduce the Air within the house , to as high a degree of Bensil , as the Air without .

THEOREM XXXI . The Pressure , and Bensil of a Fluid , that 's in the Lowest foot , is equivalent to the weight of the whole Pillar above . Figure 5.

FOr understanding this Proposition , let us suppose EF to be the lowest foot of a Pillar of Air , cut off from the rest , and inclosed in the Vessel EF , six inches in Diameter , or wideness , and twelve inches high . Now I say , the Bensil and Pressure , that 's in that one foot of Air , is exactly of as great force and power , as is the weight of the whole Pillar of Air , from which it was cut off . Let AB be that Pillar of Air , which I suppose is six inches thick , and six thousand fathom high . Take it , and weight it in a Ballance , and say it weighs 500 pound , yet the Pressure , and Bensil , that 's in the Air EF , is of as much force : and if the one be of strength by its weight , to move , v. g. a great Clock , the other by its Bensil , will be of as much . This proposition is true also in order to Water . For put the case EF , were the lowest of 34 foot of Water : in it will be found as much Pressure , and force , as will be equivalent to the weight of the whole thirty three foot , from which it was cut off . But here occurreth a difficulty ; for if the Pressure , and Bensil of the foot of Air EF , be equivalent to the weight of the whole Pillar of Air AB , which weighs 500 pound , then must the slender Pillar of Air CD , that 's but two inches in diameter , be as heavy weighed in a ballance , as the thicker Pillar AB , which is absurd . I prove the connexion of the two parts of the Argument thus : as the Bensil of the Air GH , is to the Bensil of the Air EF , so is the weight of the Pillar CD , to the weight of the Pillar AB : but so it is , that the Bensil of the Air GH , is equal in degree to the Bensil of the Air EF , according to the Theorem 21. Where it 's said , that the Pressure of Fluids may be as much , in the least part , as in the whole : therefore the Pillar CD , and the Pillar AB , must be of equal weight , when both are weighed together in the opposite scales of a Ballance , which is false , seing the one is far thicker , and so heavier then the other . There 's no way to answer this objection , but by granting the Air GH , and EF , to be equal in Bensil , and yet the two Pillars unequal in weight , because according to the 22 Theorem , the Bensil of a Fluid is one thing , and the natural weight is another .

THEOREM XXXII . In all Fluids there is a Pondus and a Potentia , a weight and a power , counterpoising one another , as in the Staticks .

THat part of the Mathematicks , which is called Staticks , is nothing else , but the Art of weighing heavy Bodies ; in which , two things are commonly distinguished , viz. the pondus and the potentia , the weight and the power . 'T is evident , while two things are counterpoising one another in the opposite scales of a Ballance , as Lead and Gold , the one being the pondus , the other the potentia . The same two are as truly found in the Hydrostaticks : for while the Mercurial Cylinder is suspended in the Torricellian Experiment , by the weight of the Air , the one is really the pondus , the other the potentia . Or while into a Siphon , with the two orifices upward , Water is poured , there arises a counterpoise , the Water of the one Leg counter-ballancing the Water of the other ; this taking the name of a pondus , the other the name of a potentia . 'T is evident also , while a surface of Water , sustains a Pillar of Water , this being the pondus , that the potentia : Or , while a surface of Water sustains a Pillar of Air , the Pillar of Air being the pondus , and the surface of Water the potentia . Or , while a surface of Quick-silver sustains a Pillar of Water or Air ; the surface is the power , and either of the two is the pondus , or weight , as you please .

THEOREM XXXIII . Fluid Bodies can never cease from motion , so long as the pondus exceeds the potentia , or the potentia the pondus .

THis is a sure Principle in the Hydrostaticks , which will appear most evident ; while we pass thorow the subsequent Experiments , I shall only now make it appear by one instance , though afterwards by a hundred . In the Torricellian Experiment , lately mentioned , 't is observed , that though the Pipe were never so long , that 's filled with Mercury , yet the Liquor subsides , and falls down alwayes till it come twenty nine inches above the surface of the stagnant Mercury below . The reason whereof is truly this , so long as the Mercury is higher then the said point , as long doth the pondus of it exceed the potentia of the Air ; therefore the motion of it downward can never cease , till at last by falling down , and becoming shorter , it becomes lighter , in which instant of time , the motion ends , both of them being now in equipondio , or in evenness of weight .

THEOREM XXXIV . When two Fluids of different kinds are in aequilibrio together , the height of the one Cylinder is in proportion to the height of the other , as the natural weight of the one is to the natural weight of the other .

FOr understanding this Theorem , we must consider , that when two Cylinders of the same kind , as one of Water with Water , or as one of Mercury with Mercury , are counterpoising one another , both are of the same altitude , because both are of the same natural weight . But when the two are of different kinds , as a Cylinder of Air with Mercury , or as a Cylinder of Air with Water , or as a Cylinder of Water with Mercury , then it will be found , that by what proportion , the one Liquor is naturally heavier or lighter , then the othe● ▪ by that same proportion , is the one Cylinder higher or lower then the other . For example , because Air is reckoned 14000 times lighter then Quick-silver , therefore the Pillar of Air that counterpoiseth the Pillar of Quick-silver in the Torricellian Experiment , is 14000 times higher . The one is 29 inches , and therefore the other is 406000 inches : which will amount to 33833 foot , or about 6766 fathom , counting five foot to a fathom . And because Air is counted 1000 times lighter then Water , therefore the Pillar of Air that sustains the Pillar of Water is 1000 times higher . The hight of Water by the Pressure of the Air is 34 foot , and therefore the hight of the Air is a thousand times 34 foot . And because Water is reckoned 14 times lighter than Mercury , therefore you will find , even by experience , that the Pillar of Water , that counterpoises the Pillar of Mercury , is 14 times higher . For if the Mercury be ten inches , the Water will be exactly 140. If it be 29 inches , the Water will be thirty four foot . The reason is evident , because if one inch of Mercury be as heavy naturally as 14 inches of Water , it follows of necessity , that for making of a counterpoise , to every inch of Mercury , there must be 14 of Water , and these in altitude , each one above another .

Hydrostatical EXPERIMENTS , For demonstrating the wonderful Weight , Force , and Pressure of the Water in its own Element .

EXPERIMENT I. Figure 6.

IN explicating the Phenomena of the Hydrostaticks , and in collecting speculative , or practical conclusions from them , I purpose to make choise of the plainest , and most easie Experiments , especially in the entry , that this knowledge , that 's not very common , and yet very useful , may be communicated to the meanest capacities . For , if at the first , any mystical , or abstruse Experiments , should be proposed with intricate descriptions , they would soon discourage , and at last hinder the ingenuous Reader from making progress . For , if a man do not take up distinctly , the Experiment it self first , he shall never be able to comprehend next the Phenomena , nor at last see the inferences of the conclusions . Next , though some of the trials may seem obvious , yet they afford excellent Phenomena , by which many profound secrets of Nature are discovered . And if that be , 't is no matter what kind they be of . Then , the grand design here , is not to multiply bare , and naked Experiments ; for that 's a work to no purpose , for it 's like a foundation without a superstructure : but the intention is , not only to describe such and such things , but to build such and such Theorems upon them , and to infer such and such conclusions , as shall make a stately building , and give a man in a short time a full view of this excellent Doctrine .

For the first Experiment then , prepare a Vessel of any quantity , as ABCD , near half full of Water , whose surface is MH . Prepare also two Glass-pipes , the one wider , the other narrower , open at both ends , which must be thrust down below the Water , first stopping the two upper orifices E and F. This done , open the said orifices , and you shall see the Water ascend in the wider to G , and in the narrower to H. Now , the question is , What 's the reason , why the Water did not ascend , the orifices E and F , being stopped , and why it ascends , they being opened ? To the fi●st part I answer , the Water cannot ascend , because the imaginary surface of Water LK is equally and uniformly prest : for with what weight the outward Water ML , and HK press the said surface , with the same weight , doth the Air within the two Pipes press it . To the second part I answer , the Water ascends , because the same surface ( the orifices E and F being opened ) is unequally prest : for the outward Water ML , and HK , press it more , then the Air within the Pipes do . The difficulty only is , why it is equally prest , the orifices E and F being stopped , and why it is unequally prest , the said orifices being once opened . To unloose the knot , I must shew the reason , why the Air within the Pipes , press the surface LK , with as great a burden , as the outward Water press it . For understanding this , you must know , that when the orifice I is thrust down below the Water , there ariseth a sort of debate between the lower parts of the Water , and the Air within the Pipes , the Water striving to be in at I , and the Air striving to keep it out : but because the Water is the stronger party , it enters the orifice I , and causeth the Air retire a little up , one fourth part , or sixth part of an inch , above I , and no more , which is a real compression it suffers . For the orifice E being stopped , hinders any more compression , than what is said ; in which instant of time the debate ends , the Air no more yeelding , and the Water no more urging ; by which means the Air having obtained a degree of Bensil , more then ordinary , by the Pressure of that little quantity of Water , that comes in at I , presseth the part of the imaginary surface , it rests upon , with as great weight , as the outward Water presseth the parts it rests upon . But when the orifice E is opened , the outward water ML , and HK , press the imaginary surface LK more , than the Air within the Pipe can do . And the reason is , because by opening the orifice above , the internal Air , that suffered a degree of Bensil more then ordinary , presently is freed , and consequently becomes of less force , and weight ; which the Water finding , that hath a little entered the orifice I , instantly ascends to G , it being less pressed , then the Water without the Pipe . Now the reason , why it ascends no higher then G , is taken from the equal Pressure of the Body that rests upon the surface MGH : For , assoon as it comes that length , all the parts of the horizontal Plain of Water , is uniformly prest with the incumbing Air , both within the Pipe , and without the Pipe . The Water in going up , cannot halt mid-way between I and G , for then there should be an unequal Pressure in Fluids without motion , which is impossible ; for the Water is still stronger then the Air , till once it climb up to G.

From this Experiment we see first , that in Water there is a Pressure and Force ; because having opened the orifice E , which is only causa per accidens of this motion , the Water is prest up from I to G. We see secondly , that Fluid Bodies , can never cease from motion , till there be an equal Pressure among the parts , which is evident from the ascent of the Water from I to G , which cannot halt in any part between I and G , because of an unequal Pressure , till it once climb up to G. We see thirdly , that Fluid Bodies do not sustain , or counterpoise one another according to their thickness and breadth , but only according to their altitude ; because there is not here any proportion between the slender Pillar of Water HK within the Pipe , and the outward Water that sustains it , I means as to the thickness ; therefore 't is no matter , whither the Glass Tubs be wider or narrower , that are used in counterpoising Fluid bodies one with another . And this is the true reason , why 't is no matter , whither the Tub of the Baroscope be a wide one , or a narrow one , seing the Air doth not counterpoise the Mercury , according to thickness , that 's to say , neither the thickness of the ambient Air that sustains , nor the thickness of the Mercury that is sustained , are to be considered ; but only their altitudes . 'T is true , the element of Air is fourteen thousand times higher , then the Mercurial Cylinder , yet there is a certain and true proportion kept between their heights ; so that if the element of Air , should by divine providence become higher or lower , the height of the Mercury would alter accordingly .

EXPERIMENT . II. Figure 6.

TAke out of the Water , the wide Pipe EGI , and stopping the orifice I , pour in Water above at E , till the Tub be compleatly full . Having done this , thrust down the stopped orifice I to the bottom of the Vessel , and there open it , then shall you see the Water fall down from E to G , and there halt . The reason is taken from unequal Pressure ; for the Tub being full of Water from E to I , that part of the imaginary surface , upon which the Pillar of Water rests , is more burdened than any other part of it , namely more then L or K ; therefore seing one part is more burdened than another , the Cylinder of Water that causeth the burden , must so far fall down , till all the parts be alike prest , in which instant of time , the motion ceaseth . This leads us to a clear discovery of the reason , why in the Baroscope , the Mercury falls from the top of the Tub of any height , alwayes to the twentieth and ninth inch , above the stagnant Quick-silver . For example , fill the Pipe NQ , which is sixty inches high with Mercury , and opening the orifice Q , the Liquor shall fall out , and fall down from N , till it rest at R , which is twenty nine inch above the open orifice Q. The reason is the same , namely unequal Pressure , seing one part of the imaginary surface of Air XS , upon which the Cylinder of Mercury stands , is more burthened then the other next adjacent : therefore , so long and so far must the Mercury subside and fall down , till the part Q , upon which the Basis of the Pillar rests , be no more burthened , than the rest of the parts ; in which instant of time , the motion ceaseth , and there happeneth an equal ballance , between the Silver within the Tub , and the Air without . If it be said , I see a clear reason , why the outward Water ML , ought to sustain the inward GI , but cannot see , why the outward Air TZS and VRX , ought to sustain the inward Mercury RX : neither do I see a reason , why it should halt at R , as the Water rests at G. I answer , though sense cannot perceive the one , as evidently as the other , yet the one is as sure as the other . For taking up the reason why it halts at R , 29 inches above X , you must remember , from the 25 Theorem , that the Pressure of the Air upon Bodies , is equivalent to the weight of 34 foot of Water perpendicularly , or 29 inches of Quick-silver . The Pillars of Air then TZS , and VRX , being as heavy each one of them , as two Pillars of Mercury , each one of them 29 inches high , it follows of necessity , that the Mercury within the Tub , must be as high as R. 'T is no wonder to see the Silver halt at R , provided RX , and ZS , were two bulks of Mercury , environing the Pipe , as the outward Water environs the wider and narrower Pipe . Neither ought any to wonder , when the Silver falls down , and rests at R , nothing environing the Pipe but Air , seing the Pressure of the Air is equivalent to the weight of 29 inches of Quick-silver . This Experiment is easily made : take therefore a slender Glass-pipe of any length , beyond 30 inches , open at both ends ; but the lower end Q , must be drawn so small by a flame of a Lamp , that the entry may be no wider , than may admit the point of a small needle , or the hair of ones head . Then stopping the said orifice , pour in Mercury above at the orifice N , till the Pipe be compleatly full . Next , close the said orifice with wet Paper , and the pulp of your finger ; and opening the lower orifice , you shall find , ( which is very delightful to behold ) the Mercury spring out , like unto a small silver threed , and falling down from the top N , shall rest at R , the motion ceasing at the narrow orifice Q. This shews evidently , that there is not need alwayes of stagnant Mercury , for trying the Torricellian Experiment ; but only when the mouth of the Pipe below is wide : for being narrow , the silver runs slowly out , and consequently subsides slowly above , and coming down slowly to R , there rests . But when the mouth is wide below , the silver falls down so quickly , that it goes beyond R , before it can recover it self , which recovery would never be , unless there were stagnant Mercury to run up again .

From what is said , we see first , that when one part of a surface of Water or Air , is more burthened than another , the burthened part presently yeelds , till it be no more burthened than the other . This is clear from the falling down of the Water from E to G , which cannot be supported by the part I , because more burthened than the rest . We see secondly , that the element of Air , rests upon the surfaces of all bodies with a considerable weight ; otherwise it could not sustain the Water , before it fall down from E to G : for if it did not rest upon the surface MH , with weight , the Water could never be suspended ; seing the application of the finger to the orifice E , is only the accidental cause of this sustentation . We see thirdly , that according to the difference of natural weight , between two Fluids , so is the proportion of altitudes between two of their Cylinders : therefore Air being reckoned 14000 times lighter then Mercury , it followes that the Cylinder of Mercury sustained by the Air , must be 14000 times lower and shorter , than the Cylinder of Air that sustaines it ; which appears from this experiment to be true , seeing by the Pressure of the Air , which is thought to be about 7000 fathom high , 29 inches of Mercury is supported between R and X. In a word , if Air be naturally 14000 times lighter than Mercury , which is very probable ; then must the altitude of it , commonly called the Atmosphere , be fourteen thousand times , nine and twenty inches , that is 406000 , or of feet 33833.

EXPERIMENT III. Figure 6.

WHile the outward , and inward Water are of the same altitude , withdraw the inward Air EG by suction , or by any other device you think fit , and you will find the Water rise as high as E , which I suppose to be 34 foot above MGH . The same Phenomenon happens , in taking the Air out of the narrow Pipe FK . The reason is still unequal Pressure ; for in removing the Air , that 's within the Pipe , the part of the surface M , and the part H , remaines burthened , while the part G is freed of its burden : therefore this part of the surface , being liberated of its burden , that came down through the Pipe , instantly rises , and climbs up as far , as the outward Air resting upon M and H , can raise it , which is to E 34 foot : for the Pressure of the Air upon the surfaces of all Waters , according to the 25 Theorem , being equivalent to the weight of 34 foot of Water , must raise the said Water in the Pipe 34 foot . You do not wonder , why it rises from I to G , as in the first experiment ; no more ought you to wonder , why it rises from G to E , seing the weight of the Air , doth the same thing , that 34 foot of Water resting upon the surface MH , would do .

From this experiment we see first , that the Pressure of the Air , is the proper cause of the motion of Water , up thorow Pumps and Siphons , or any other instrument , that 's used in Water-works of that kind ; for if the weight of the Air , resting upon the surface MH be the cause , why the Water climbs up from G to E , the same must be the cause , why the stagnant Water followes the Sucker of the Pump , while it 's pulled up . And the same is the cause , why Water ascends the Leg of a Siphon , and is the cause , why motion continues after suction is ended . We see secondly , that every Pressing Fluid hath a Sphere of activity , to which it is able to raise the Fluid , that is pressed . This is evident in this experiment , because the Pressure of the Air resting upon MH , is able to raise the Water , the hight of E in the wide Pipe , and the hight of F in the narrow , and no further , even though the said Pipes were far longer : and this altitude and highest point is precisely 34 foot between Air and Water . We see thirdly , that 't is all one matter , whether Pumps and Siphons be wider or narrower , whether the tub of the Baroscope be , wherein the Mercury is suspended , of a large Diameter , or of a lesser Diameter . This is also evident from the same experiment ; seing there is no more difficulty in causing the Water ascend the wide Pipe , than in causing it ascend the narrow one . And the reason is , because the pressing Fluid repects not the pressed Fluid , according to its thickness and breadth ; but only according to its altitude . Therefore'its as easie for the Air , to press up Water through a Pump four foot in Diameter , as to press it up through a Pump , but one foot in Diameter .

EXPERIMENT IV. Figure 7.

THis Schematism represents a large Vessel full of Water , whose first and visible surface is DEHK . The second , that 's imaginary is , LI , six foot below it . The third of the same kind , is MG , six foot lower . The fourth , is NFO , six foot yet lower . The last , and lowest , is ABC . There are here also four Tubs , or rather one Tub under four divers positions , with both ends open . After this Tub DA is thrust below the Water , till it ascend , as high as D in it , lift it up between your fingers , till it have the position of the second Pipe EF , and then you shall see , as the orifice of the Pipe ascends , the Cylinder of Water fall out by little and little , until it be no longer than EF. Again , lift it further up , till it have the position of the Pipe HG , then shall you find the Cylinder of Water become yet shorter . Lastly , if it be scituated , as the Pipe KI , the internal Water becomes no longer than KI . The reasons of these Phenomena are the same ; namely unequal Pressure ; for the Orifice A being lifted up as high as F , it comes to the imaginary surface NO , which is not under so much Pressure , as the other is ; therefore one part of it being more burdened , than another , namely the part upon which the Cylinder of Water rests , it presently yeelds , and suffers the Cylinder to become shorter , and lighter , till it become no heavier , then is proportionable to its own strength . To make this reason more evident , it is to be noted , that no surface of Water is able to support a Cylinder higher then its own deepness , that is to say , if a surface be 40 foot deep , it is able to sustain a Cylinder 40 foot high , and no more : therefore the surface NO , being but 18 foot deep , it cannot sustain a Cylinder 24 foot long : for if that were , then the Potentia , should be inferiour to the Pondus , which is impossible in the Hydrostaticks . In effect , it were no less absurdity , then to say , 18 ounces are able to counterballance 24. For a second trial , lift up the same Pipe higher , till it acquire the position of the Tub GH ; in this case , the Cylinder of Water within it , becomes yet shorter , even no longer , than GH . The reason is the same , namely unequal Pressure ; for when a Cylinder of Water 18 foot high , comes to rest upon this surface , that is but 12 foot deep , it makes one part of it more burdened then another ; therefore the part that is more prest , presently yeelds , and suffers the Cylinder to fall down , till the Pondus of it , become equal to its own Potentia . For the last trial , lift up the Tub , till it acquire the position of the Pipe KI : in this case , the Water within it becomes no longer then KI , the surface LI , that is but six foot deep , not being able to sustain a Cylinder 12 foot high .

From this Experiment we see first , that in all Fluid Bodies there is a Pressure , which is more or less , according to the deepness of that Fluid ; this is evident from the four several surfaces ; there being more Pressure and force in the lowest ABC , then in the next NO ; and more in this , then in the surface MG ; and more in this , then in LI. We see secondly , that in all Fluids , there is a Pondus and a Potentia ; which two are alwayes of equal force , and strength ; the Potentia is clear and evident in the surface , by supporting the Pillar ; which Pillar is nothing else , but the Pondus supported . And that they are alwayes of equal strength , is most evident also ; for when you endeavour to make the Pondus unequal to the Potentia , in making a surface 18 foot deep , to support a Pillar 24 foot high , they of their own accord become equal ; the Pillar becoming shorter , and suitable to the strength of the surface that sustains it . We see thirdly , that 't is impossible for one part of the same Horizontal surface , to be more burdened then another : for when you endeavour to do it , by setting a longer Pillar upon it , the part burdened instantly yeelds , till it be no more prest , then the next part to it . We see fourthly , that the inequality , that is between the Pondus and the Potentia in Fluids , is the proper cause of the motion of Fluids . For when you endeavour to make a surface 30 foot deep , sustain a Pillar 40 foot high , this inequality is the true cause , why the Pillar subsides , and falls down , and why the surface yeelds , and gives way to it . And this inequality is the true cause , why the motion of Water thorow Siphons continues . For understanding this , you must conceive a Siphon , to be nothing else , but a crooked Pipe with two legs , the one drowned among Water , the other hanging in the open Air. The use of it is , for conveying Wine or Water from one Vessel to another , which is easily done by suction . Now after suction is ended , the motion of the Water continues , till the surface become lower , then the orifice out of which it runs . The true reason then , why the Water flows out , is the inequality between the Potentia of the Air , and the Pondus of the Water ; the Pondus being stronger then the Potentia . For in Air as in Water , we must conceive Horizontal surfaces ; and these surfaces to be endowed with Pressure and force , as are the surfaces of Water . Now when the leg of a Siphon is hanging in the Air , it must rest upon one surface or another , and consequently the Water in it , must rest upon the same surface . If the Potentia of the surface be stronger , then the Pondus of the Water ; the Water is driven backward , which alwayes comes to pass , when the orifice is higher , then the surface of the Water of the Vessel , among which the other leg is drowned . If the Potentia of the surface of that Air , be of equal power and strength , with the Pondus of the Water , the Water goeth neither backward , nor forward , but stands in equilibrio : this happens , when the orifice is neither higher , nor lower , than the surface of the Water in the Vessel . But if the Potentia of the surface of the Air be weaker , than the Pondus of the Water ; in this case , the Air yeelds , and suffers the Water to run out , even as a surface 30 foot deep , yeelds to a Pillar of Water 40 foot high . The same inequality is the reason , why Water climbs up the Pump ; why Water climbs up a Pipe , when a man sucks with his mouth . Before suction , the Potentia that 's in the surface of Water , among which the end of the Pipe is drowned , is of equal force with the Pondus of the Pillar of Air , that comes down thorow the Pipe , or Pump ; but assoon as a man begins to suck , the said Pillar of Air becomes lighter ; and the Water finding this , presently ascends . The same is the reason , why the Mercury falls down to 29 inches in the Baroscope , and no further : for as long as the Pondus of the Pillar of Mercury , exceeds the Potentia of the surface of Air , so long doth the motion continue ; and when both are become equal in force , the motion ceaseth . When the Glass-tub is 40 inches long , and filled with Mercury , and inverted after the common manner , you are endeavouring as it were , to cause a surface 29 inches deep , sustain a Pillar 40 inches high , which is utterly impossible in Fluids . It is judged by many a wonder to see the deflux of the Mercury in the Baroscope ; but in effect , there 's no more cause of admiration in it , than to see the Cylinder of Water grow shorter , by lifting the Pipe up from one surface to another .

From this Experiment , we see the true reason , why the Mercurial Cylinder of the Baroscope becomes shorter and shorter , according as a man climbs up a mountain with it . For at the root of the hill , the surface of Air , that sustains the Pillar of Mercury , is of greater force , than the surface at the middle part : and this is stronger than any surface at the top . The Pipe therefore being carried up from one surface to another , the Mercury in it , must subside , and full down , even as the Water falls down , and becomes shorter , by lifting the Pipe from the surface ABCD to the surface NO . And as the whole Water would fall down , if the orifice I , were lifted above the surface DEHK , so i● the Baroscope could be carried so high , till it came above the top of the Air , the whole Mercurial Cylinder would surely fall down . And as by thrusting down the said Pipe to the bottom of the Vessel again , as the Pipe DA , the Water ascends in it ; so by bringing down the Baroscope to the earth again , the whole 19 inches would rise again .

EXPERIMENT V. Figure 8.

FIll the Vessel ADGH with Water to the brim . Next , thrust down the open orifice of the Tub DA , to the bottom , and you shall see the Water ascend in it , as high as D , according to the first experiment . When this is done , recline the said Pipe , till it ly as BE , and you shall find the Pipe , compleatly full of Water . Next , erect the same Tub again as DA , and you shall see the Cylinder of Water fall down , and become shorter , as at first . For salving this Phenomenon , and such like , I must suppose this Water to be 50 inches deep , and the Tub IA , and BE 90 inches long : and the said Tub in reclining , to describe the quadrant of a Circle FEG . Now the question is , why there being but 50 inches of Water in the Tub , while erected , there should be 60 in it , when it is reclined ? Secondly , why there should be 90 inches of Water in the Tub BE , and but 50 in it , when it stands Perpendicular , as DA ? If you reply , because there are 90 inches in recta linea between the point B , and the point E , and but 50 between A and D. But this will not answer the case ; because , if you stop the orifice E , with the pulp of your Finger , before it be erected , you will find the Tub remain full of Water , even while it stands Perpendicular ; and fall down , when the orifice is opened . Or , while the Tub stands Perpendicular , stop the orifice I , and recline it as BE : yet no more Water will be found in it , than 50 inches : but by unstopping the said orifice , the Water climbs up from R to E , and becomes 90 inches . Now , what 's the reason , why it runs up from R to E , and why it falls down from I to D ? I answer then , the Water must run up from R to E , because of the inequality , that 's between the Pondus of the Cylinder BR , and the Potentia of the surface of Water ABC , that supports the said Cylinder . For understanding this , know , while the Tub is erected , there is a perfect equality , between the weight of the Pillar AD , and the force or Power of the surface that sustains it , seing a surface 50 inches deep , supports a Pillar 50 inches high . But assoon as the Tub is reclined , there arises ane inequality between the saids two parties , the Pondus of the Cylinder becoming now less than before . If you say the quantity of the Water is the same , namely 50 inches , in the reclined Tub , as well as in the Perpendicular . I grant the quantity is the same , but the weight is become less . Now the reason , why the same individual Water , is not so heavy as before , is this ; there are 40 ounces of it , supported by the sides of the Tub within ; which were not , while the Tub was erected : for in this position , the whole weight of the Cylinder rests upon the surface : but while the Tub is reclined , the said surface is eased , and freed of 40 ounces of it ; this 40 , resting and leaning upon the sides of the Pipe within . The surface then , finding the said Cylinder lighter now than before , instantly drives it up from R to E , 40 inches . And likewise , when the reclined Pipe is made Perpendicular , the Water falls down from I to D , because of the inequality , that 's between the Pondus of the Pillar , and the Potentia of the surface ; this surface 50 inches deep , not being able to support a Pillar 90 inches high , for if this were , then one part , should be more burthened than another , which is impossible .

It is to be observed , that by how much the more , the Tub is reclined from a Perpendicular , towards the horizontal surface ABC , by so much the more growes the inequality , between the Pondus and the Potentia , and that according to a certaine proportion Hence is it , that the Tub being reclined from 60 degrees to 50 , there arises a greater inequality between the Pondus of the Cylinder , and the Potentia of the surface , than while it is reclined from 70 to 60 : and more yet in moving from 50 to 40 , than in moving from 60 to 50 , and so downward , till it be horizontal , in which position , the whole Pondus is lost . And contrariwise , while the Pipe is elevated , the Pondus begins to grow ; and growes more , being lifted up from 10 to 20 , than from 1 to 10 : and yet more in travelling from 20 to 30 , than from 10 to 20 , and so upwards , till it be Perpendicular , in which position , the Cylinder regaines the whole Pondus and weight , it had . This proportion is easily known , for it s nothing else , but the proportion of Versed Sines upon the line FB ; for according to what measure , these unequal divisions become wider , and wider from 90 to 1 , according to the same proportion does the Pondus of the Cylinder become less and less : and contrariwise , according to what proportion the said divisions become more and more narrow from 1 to 90 , according to the same measure and rate , does the Pondus of the Cylinder become greater and greater .

From this experiment we see first , that two Cylinders of Fluid bodies , differing much in quantity , may be of the same weight : because though the Cylinder BE 90 inches long , be far more in quantity , than the Cylinder DA , that 's but 50 , yet both of them are of the same weight , in respect of the surface that sustaines them . If it be said , the one is really heavier , than the other , notwithstanding of all this . I answer , it is so indeed , in respect of the Libra , or Artificial Ballance , that we commonly use in weighing of things : but it is not so in respect of this Natural Ballance , if I may so speak , wherein Fluid bodies are onely weighed after this manner . We see secondly a clear ground for setting down the ninth Theorem , namely , that in all Fluid bodies a twofold weight may be distinguished , one Sensible , another Insensible : because the Sensible weight of the Cylinder of Water BE , remaines still the same , even though it should be reclined to G ; for take it out , and weigh it in a Ballance , it will be as heavy the one way as the other . But it is not so with the Insensible weight ; seeing the Tub begins no sooner to recline , but assoon it begins to diminish , and grows less . This Insensible weight is nothing else , but the sensible weight considered after another manner . For look upon the weight of the Pillar of Water BE , as it weighs in a pair of Scales , it is then Sensible , and weighs so many ounces , and cannot be more or less : but look upon it in reference to the Potentia of the surface , that sustains it , it is then Insensible as to us : for though a man should put his hand below the Water , and endeavour to find the weight of the said Pillar , yet he shall not find it , though that part of the surface upon which it rests , doth really ( if I may so speak ) find the weight of it . And as it is Insensible , so is it sometimes more , and sometimes less , according as the Tub is elevated , or reclined : now these two being put together , gives a very probable ground for this distinction . We see thirdly , that the Pondus or weight of Fluids , doth not only press according to Perpendicular lines , but according to lines falling obliquely upon the imaginary surface ; so doth the weight of the Pillar of Water BE , press the surface ABC . We see fourthly , that Fluid Bodies , do counterpoise one another , according to Altitude only : for put the case , the Pipe BE , were ten times wider then it is , yet will the surface sustain the Water in it , provided the Pipe keep still the same position of Altitude , namely 50 degrees : the reason seems to be this ; for if the Base of the Pillar become more in Diameter , it necessarily requires a larger part of the surface to rest upon ; which larger part is really stronger than the lesser part , as will be shewed afterwards . From this Experiment we see lastly , an evident reason , why the Mercurial Cylinder in the Baroscope runs up , and fills the empty space , when the Pipe is reclined , and why it runs down , when the Tub is erected again . In effect , the reason is the same , namely , an inequality between the Pondus of the Quick-silver , and the Potentia of the surface of the Air : for when the Tub begins to recline , the Pondus begins to rest upon the side of the Tub within ; by which means the Potentia of the surface finding the burden less , instantly thrusts up the stagnant Mercury to supply that loss , seing two Fluids cannot counterpoise one another , unless they be in aequilibrio . And contrariwise , assoon as the Tub begins to be erected , the Pondus of the Mercury begins to grow , and so overcomes the Potentia of the surface , till by falling down it can do no more .

EXPERIMENT VI. Figure 9.

THis Schematism represents a Vessel full o● Water , whose first and visible surface is HIK ; the second , which is imaginary , is EFG : the third , ABCD.

Fig. 5 Pag. 32

Fig. 6 Pag. 37

Fig. 7 Pag. 46

Fig. 8 Pag. 55 Besides these three in Water , conceive a fourth in the Air , above the Water , namely LMN . Upon this aërial surface , rests the orifice M , of the Tub TM , open above . Upon the surface EFG , is standing the mouth F , of the Pipe SF . And upon the surface ABCD , stands the Pipe RB , open at both ends . After the orifice B is drowned below the Water , you will find the Liquor rise from B to H. Then close with the pulp of your Finger the mouth R , and lift the Pipe so far up , till it have the Position of the Pipe SF ; and you shall see the Water hing in it between F and O. Lastly , bring the said orifice compleatly above the Water , till it have the position of the Tub TM ; yet shall the Water still hing in it , as MP . The first question is , what sustains the Water IO ; for the part FI , is sustained by the ambient Water ? I answer , it cannot be the pulp of the Finger closing the orifice S ; for though , by taking away the Finger , the Water OI falls down , and by putting to the Finger , it is keeped up , yet this proves not the pulp of the Finger to be the principal , and immediat cause . I say then , the Water OI is suspended by the weight of the incumbing Air , resting upon the surface HIK . For understanding this , consider , as I said before , 25. Theorem , that the Pressure of the Air upon all Bodies , is just equivalent to the weight of 34. foot of Water . Hence then is it , that if the Air be able to sustain a Pillar of Water , 34 foot high , it must be able to sustain the short Pillar OI , that exceeds not four foot . The second question is , whether the part F , be equally burthened with the part E , or G ; for it would seem not , seing the Water OIF , is but four foot high ; whilest upon E or G is resting , not only more then a foot of Water to the top HIK , but the whole weight of the Atmosphere upon the said top is resting , which is equivalent to the burden of 34 foot of Water . I answer , there 's more to be considered , than that four foot of Water , which in it self is but of small burden , therefore to this we must add the weight of the Air between O and S , within the Pipe ( remember that the orifice S is stopped with the pulp of the Finger ) which in effect will be as heavy as 31 foot of Water . Put the case then , F , to be one foot below the first surface HIK , and the Water OI to be three foot , then ought the Air OS , to have the weight of 31 foot , because the surface EFG is able to support a Pillar of 35 foot . This I prove , because the part E , de facto , sustains 35 foot , because the Air above is equivalent to 34 foot of it , and there is a foot of Water between it and the top , namely between E and H. The third question is , how it comes to pass , that the Water still remains in the Pipe , after the orifice M is brought above the surface of the Water ; for there is here no stagnant Water guarding it , as guards the orifice F. I answer , that the base M , of this Pillar of Water PM , as really rests upon the horizontal surface of this Air LMN , as a Cylinder of Brass or Timber rests upon a plain Marble Table , and after the same manner . Remember that the orifice T is stopped all this time , with the pulp of the Finger . If it be said , that the part M , is more burdened then the part N , seing it sustains four foot of Water , which the part N supports not , and the Air PT within the Pipe also , which is of as much Bensil and Pressure , as the Air NY is of . For clearing of this difficulty , consider , that the Pillar PM is shorter now than before ; for the orifice M coming up from D , some inches of Water falls out , as will be found by experience . Suppose then , that of four foot , six inches fall out ; if this be , then the inclosed Air between P and T , must be six inches longer , if this be , then of necessity the Bensil of it must be proportionably remitted and slackened : whence follows by Metaphysical necessity , that it cannot burden the Water PM , with as much weight as it had , and consequently the surface of Air cannot be so much burdened . It must then be no more bu●dened with them both together , than it is with the single Pillar of Air YN . If then the Water PM , be three foot and an half , the weight of the enclosed Air TP , must be exactly the weight of thirty foot of Water and an half .

From this experiment , we see first the Pressure of the Air , for by it the Water OI is suspended , and by the same pressure is the Water PM suspended . We see secondly , that in Air , there is a power of dilating it self , and that this dilatation never happens , without a relaxation of the Bensil . We see thirdly , that one Fluid cannot sustain another , unless the Potentia of the one , be equal to the Pondus of the other , as is clear from the Aërial surface , that cannot sustain the whole four foot of Water , but suffers six inches of it to fall out , that the Pondus of the rest , and the Air above it , may become equal to its own Potentia . We see fourthly , that Fluid Bodies have not only a power of pressing downward , but of pressing upward likewise : as is clear from the Water OI , that 's suspended by the Air pressing down the surface of Water HIK . It presseth upward also , while it supports the Water PM . This Experiment also answers a case , namely , whether or not , it is alwayes needful to guard the orifice of the Tub of the Baroscope with stagnant Quick-silver ? I say then , it is not alwayes needful , provided the orifice be of a narrow diameter ; for experience tells , that while it is such , the Mercury will subside , and halt at 29 inches above the orifice , though no stagnant Mercury be to guard . In making this trial , the orifice must be no wider , than may admit the point of a needle . Or suppose it to have the wideness of a Tobacco-pipe , yet will the Mercury be suspended , though the end be not drowned among stagnant Quick-silver , even as the Water PM , is kept up without stagnant Water about it . For trial of this , you must first let the end of the Pipe , be put down among stagnant Mercury , and after the Cylinder is fallen down to its own proper altitude , lift up the Pipe slowly , till the orifice come above the surface , and you will find , provided you do not shake the Pipe , the Cylinder to be suspended after the same manner , immediatly by the Air , as the Water PM is .

EXPERIMENT VII . Figure 10 , 11.

TAke a Vessel of any quantity , such as ABCDE , and fill it with Water . And a Glass-pipe , such as GFD , of 15 or 20 inches long , of any wideness , closs above , and open below . Before you drown the open end among the Water , hold the Glass before the fire , till it be pretty hot , and having put it down , you will see the Water begin to creep up till it come to F , where it halts . The question now is , what 's the reason , why the Water creeps up after this manner , 10 or 12 inches above the surface AB ? I answer , the heat having ra●ified the Air within , and by this means , having expelled much of it , and the Air now contracting it self again with cold , the Water ascends , being prest up with the weight of the incumbing Air , resting upon the surface of Water AB . There is here surely an inequality between a Pondus and a Potentia , that must be the cause of this motion . I judge then the inequality to consist between the weight of the Air within the Pipe , and the surface of Water CDE . To explicate this , I must suppose the Pipe to be thrust down cold ; in this case , little or no Water can enter the orifice D. And the reason is , because the Pondus of the Air within the Glass , is equal to the Potentia of the surface CDE . But when the Pipe is thrust down hot , much of the Air having been expelled by the heat , and now beginning to be contracted by cold , the Pondus of the Air becomes unequal to the Potentia of the surface , and therefore this , being the stronger party , drives up the Air within the Glass , till by this ascent , the Pondus of the Air GF , and the Pondus of the Water FD together , become equal to the Potentia of the surface CDE , that sustains them . For a second trial ; bring a hot coal neat to the side of the Glass , between G and F , and you will find the Water to creep down from F toward the surface AB ; and if it continue any space , it will drive down the whole Water , and thrust it out at D. To explicate this , I must suppose that heat , by rarifying the Air within the Glass , intends and increaseth the Bensil of it , and the Bensil being now made stronger , there must arise an inequality between the Pondus of the said Air , and the Potentia of the surface CDE ; the Air then , being the stronger party , causeth the surface to yeeld .

By comparing this Experiment with the former , we see a great difference between the dilatation of Air , of its own accord , and by constraint . For while it is willingly expanded , the Bensil begins to grow slack , and remiss , and loseth by degrees of its strength ; even as the Spring of a Watch by the motion of the Wheels , becomes remiss . But when the dilatation is made by heat , and the Air compelled to expand and open it self , the Bensil becomes the stronger , and the Pressure the greater . Notwithstanding , though the Bensil of this inclosed Air GF , may be made stronger by heat , to the expulsion of the Water FD , yet if this rarefaction continue any time , the Bensil becomes dull and slack . And the reason is , because Air cannot be expanded and opened to any quantity ; an inch cannot be dilated and opened to an hundred , or to a thousand : neither can the Bensil of it be intended , and increase to any degree , v.g. from one to 20 , 30 , or 100. And therefore , as the expansion grows , the Bensil must at length slacken . But if so be the Air were inclosed , as in a bladder knit about the neck with a string , then the more heat , the more Bensil : for in this case there is a growth of Pressure , without dilatation . And sometimes the Bensil may be so intended with the heat , that the sides of the bladder will burst asunder .

From this Experiment we see first a confirmation of the 21 Theorem , namely , that there may be as much Bensil and Pressure , in the smallest quantity of a Fluid , as in the greatest ; as is clear from the Bensil of the Air GF , which in effect counterpoiseth the weight of the whole Atmosphere , resting upon the surface of Water AB . We see secondly , that when the pondus , and the potentia of two Fluids , are in equilibrio , or of equal strength , a very small addition to either of them , will cast the ballance . For if a man should but breath softly upon the side of the Glass between G and F , or lay his warm hand to it , the said Air will presently dilate it self , and by becoming thus stronger , thrust down the Water , and so overcome the potentia of the surface . We see thirdly a confirmation of the sixth Theorem , namely , that the Pressure of Fluids is on every side ; as is clear from the inclosed Air GF , that not only presseth down the Water FD , but with as great force presseth up the top of the Glass within , and presseth upon all the sides of it within , with the same force . This Experiment also , leads us to the knowledge of two things : First , of the reason , why with cold the Water ascends in the common Weather-glasses ; and why in hot weather the Water descends . Secondly , from this Experiment we may learn to know , when the Air is under a greater Pressure , and when under a lesser : because when the Air becomes heavier , as in fair weather , the Water creeps up in some measure , it may be two or three inches ; when there is no alteration as to heat and cold : and in foul weather , or in great winds , when the Air is really lighter , the said Water creeps down as much . If it be asked , how shall I know , whether it be the cold of the Air , or heaviness of the Air , that causeth the Water to ascend ; and whether it be the heat of the Air , or the lightness of the Air , that causeth the Water to descend ? I have proposed this question of purpose , to let you see a mistake . Many believe , that the ascent and descent of Water in common Weather-glasses , is allanerly from the heat and coldness of the Air ; and therefore they conclude a cold day to be , because the Water is far up : whereas the Water hath ascended since the last night , by reason of a greater weight in the Air , which alwayes is , when the weather is dry , and calm , though there hath been no alteration of heat to cold . If it be asked , how come we to the knowledge of this , that the pressure and weight of the Element of Air , is sometimes less , and sometimes more ? I answer , this secret o Nature , was never discovered , till the invention of the Torricellian Experiment , otherwise called the Baroscope . For after the falling down of the Quick-silver to 29 inches ▪ if you suffer it to stand thus in your Parlour or Chamber , according as the Pressure , and weight of the Element of Air , becomes more or less , so will the Altitude of the Mercury become less or more , and vary sometimes above 29 inches , and sometimes below . This alteration is very sensible , which is sometimes the tenth part of an inch , sometimes the sixth , and sometimes the third , according as the weight of the Air is less or more . From December to February , I found the alteration become less and more from 30 inches to 28 , which will be three fingers breadth . The common Weather-glasses then are fallacious , and deceitful , unless they be so contrived , that the Pressure of the Air cannot affect them , which is easily done by sealing them Hermetically , and in stead of common Water , to put in Spiritus Vini rectificatissimus , or the most excellent Spirit of Wine , and strongest that can be made .

It may be here inquired , whether or not , Mercury would ascend in this Glass , as the Water does ? I answer it would ; because the ascent depends only upon the Pressure of the Air , incumbing upon the stagnant Liquor in the Vessell , that 's able to drive up Mercury as well as Water . It may be inquired secondly , how far Mercury will ascend , and how far Water will creep up ? I answer , Mercury can ascend no higher in a Tub , than 29 inches ; and Water no higher , than 34 foot ; and this onely happens , when there is no Air above the tops of the Cylinders to hinder their ascents . But when there is Air , as GF above the liquor , it can go no higher , than the point to which the cold is able to contract the inclosed Air , which is in this Glass , the point F. It may be inquired thirdly , which is the greater difficulty , whether or not Mercury , will rise as easily in a Tub as Water ; for seeing , it s 14 times heavier , it seemes the Air should have greater difficulty to press it up , than to press up Water ? I answer , 't is greater difficulty for the Air to press up 20 inches of Mercury , than to press up 20 inches of Water ; yet it s no greater difficulty , for the Air to press up 20 inches of Mercury , than to press up 23 foot of Water , because the burden and weight is the same . It may be inquired fourthly , whether or not , it be as easie for the Air , to press up a thick and gross Cylinder of Water , as to press up a thin and slender one ? For example , whether is it as easie for the Air to press up a Cylinder of Water 10 inches in Diameter , and 10 foot high , as it is to press up one , two inches in diameter , and 10 foot high ? I answer , there is no more difficulty in the one , than in the other : and the reason is , because Fluid bodies do not counterpoise one another according to their thickness , but only according to their altitude , according to the fourth Theorem . Therefore seeing the slender Cylinder is as high as the grosser , it must be no more difficult to the Air , to press up the one then the other .

There is one difficulty yet remaining , which is truely the greatest of all ; namely what 's the reason , why its more difficult to the Air , to press up 20 inches of Mercury , than to press up 20 inches of Water : or more difficult to the Air , to press up 20 inches of Mercury , than to press up 10 ? I answer , this comes to pass , because the Air is more burthened with 20 inches of Mercury , than with 10. Now , if this be , then surely it must be more hard to the Air , to do the one , than to do the other : even as it is more hard ; for a man , to lift up from the ground , 20 pound of iron , than to lift up 10 or 15. The case may be better illustrated after this manner . Suppose a man standing on the ground , with a rope in his hand , coming down from a Pulley above , drawing up a weight to the top of the house : put the case likewise , the weight be a stone of 20 pound , and the weight of it , to increase successively , as it is pulled up . Now its easie for the man to pull up the stone the first fathom ; because it is but 20 pound weight : but the stone becoming 40 pound in the second fathom , and 60 in the third , and 80 in the fourth and so forth , untill it become 1000 , he will find the greater difficulty , the longer he pulls . 'T is just so with Air , or Water , raising Mercury in a Tub ; for as the Cylinder of the Mercury grows higher by rising , so it becomes heavier , and consequently the imaginary surface , upon which the Base of the Pillar rests , is more and more burdened , and so becomes less and less able to press it up . This leads us to a clear discovery of the reason , why 't is more difficult by suction , to pull up Mercury in a Pipe , than to pull up Water ; and more hard to suck up ten foot of Water , then to suck up five . For trial of this , which is soon done , take a slender Glass-pipe 30 or 40 inches long , open at both ends , and drown the one end among Quick-silver , and put your mouth to the other , and having sucked , you will find greater difficulty to pull up thorow the Pipe 15 inches of Mercury , than to pull up 10 , or 8 ; and far greater difficulty to suck up 20 , than to pull up 15. It may be objected , that if a man had strength sufficient in his Lungs , to suck out the whole Air of the Pipe , thirty inches of Mercury would come as easily up , as three , which seemes to prove , that the difficulty of the Mercurie's up-coming , depends not upon the weakness of the Air , but upon the weakness of the Lungs , and want of strength to suck . I answer , though a man were able to suck out the whole Air of the Pipe , yet 30 inches , will never ascend so easily , as ten , nor ten so easily as three ; and that for the reasons already given . But why is it then , ( say you ) that the stronger the suction be , the higher the Mercury ascends in the Pipe ? I answer , the suction serves for no use , but to remove the impediment , that hinders the Mercury from coming up , which is nothing else , but the Air within the Pipe . Now , the more of this Air that 's taken away by suction , ( the stronger the suction is , the more Air is taken away ) the farder up comes the Mercury . But why ought there to be difficulty in the suction of Mercury , to the altitude of 15 or 20 inches , more than in the suction of Water to that altitude ? I answer , when I suck Water up thorow a Pipe , the suction of the Air above it , is easie ; because the ascending Water helpes much to drive it up to the mouth , the outward Air driving up both . But the suction is difficult in Mercury , because the ascending liquor , does not help so much , to drive up the Air to the mouth , as the Water does . And the reason is , because the Air , being more burdened with 15 inches of Mercury , than with 15 inches of Water , cannot so easily drive up the one as the other , and so Mercury cannot so easily drive up the Air of the Pipe to the mouth , as Water does . In a word , according to the difference of specifick weight , between Water and Mercury , so is the difficulty of suction ; therefore , because Mercury is 14 times heavier than Water , there is 14 times more difficulty , to pull up the one , than the other . Note , that suction is not taken here strict●y , as contradistinguished from pulsion ; but in a large sense , as it may comprehend it .

To proceed a little further , let us suppose the Pillar of Mercury ( see the 11. Figure ) GH , that 's raised by the surface of Air FG , to be 29 inches , and every inch to weigh one ounce . Secondly , that the said surface has 29 degrees of power or force in it : for in all counterpoises the Pondus and the Potentia are equal ; therefore , if the Mercury be 29 inches , the Potentia of the surface must have 29 degrees of strength or force in it , to counterballance the Pondus . These things being supposed , which are evident , let us imagine the surface of Air , to raise the Mercury one inch above FG. In this case , the surface is weaker than it was ; which I prove evidently , because it is now but able to raise 28 of Mercury . Imagine next , the said surface to have raised the Mercury two inches above FG , then it follows , that it must be yet weaker , because it 's now but able to raise 27 inches : for by supporting two ounce of the Pondus , it loseth two degrees of it's own Potentia . In raising three inches of Mercury , it is three degrees weaker ; and in raising four , it is four degrees weaker , and so forth ; therefore , having raised 28 inches , there is but one degree of force remaining in the surface . And when it hath raised the whole , namely 29 , it is no more able , and can no more press . For confirmation , put the case that the surface of Air FG , were as able , and had as much Pressure in it , after it hath raised 29 inches of Mercury , as it is after the raising of 10 ; then it follows of necessity , that after the raising of 20 , it shall raise 19 moe , which is impossible , seing the greatest altitude is 29. It follows of necessity , ( I say ) because after the raising of 10 , it is able to raise 19 moe : therefore if it be as able after 20 , as after 10 , it must raise 19 after 20. Yea , if it be as able after 20 as 10 , it must be as able after 29 as 10. If this be , then it may raise other 29 , and a third 29 , and so in infinitum . Therefore , I conclude , that when two Fluid Bodies are in equilibrio one with another ; or when the pondus is equal to the potentia , none of them doth actually press upon another , at least the su●face hath lost all its Power and Pressure , which is also evident in the Pillar . For understanding this , let us suppose ACB ( Figure 11. ) to be a Pipe 58 inches long , and full of Mercury , and every inch of it to weigh one ounce . Now , when the orifice D is opened , there is here as great an inequality , between the pondus and the potentia of the surface of Air EB , on which it rests , as was between the surface FG , and the pondus of Mercury HG . For as FG had 29 degrees of power to raise GH , so the Pillar AB has 29 ounce of weight , to overcome the surface EB . And as the surface FG , became one degree weaker , by raising one inch of the Mercury HG , and two degrees weaker , by raising two inches , and so forward , till it lost all its Pressure ; so the Pillar , by falling down one inch , loseth one ounce of the weight ; by falling down two , it loseth two ounce , and so forward , till by falling down from A to C , it loseth all its Weight and Pressure .

But here occurreth a difficulty ; for if the surface FG , hath lost all its Pressure , by raising the Mercury from G to H ; and if the Pillar CB , hath lost all its Pressure , by falling down from A to C ; it follows , that when a Pillar of a Fluid , and a surface of a Fluid are in equal termes , or b●ought to an equipondium , there is no Pressure in them at all . For answer , consider first , that in all counterpoises , there a●e necessarily two things , the movens and the motum , the thing that moves , and the thing that is moved . Secondly , you must consider the motum , to have a pondus or weight in it , and the movens to have a potentia , or power , wherewith it moves that weight . Thirdly , that as the thing that moves , hath a power or force in it self , whereby it moves , so the thing that is moved hath a power or force in it self , whereby it resists the motion . Fourthly , that sometimes the resistance of the thing moved , may exceed the power of the movent , as when a Quarrier with a Leaver , endeavours to prize up a stone too heavy for him : or the power of the movent , may exceed the resistance of the weight ; or both may be of equal power . Consider fifthly , that as the pondus of the thing moved , begins to grow more and more , so the power of the movent decreaseth proportionably ; not absolutely , as heat is extinguished in Water by the cold Air , when it is removed from the Fire , but respectively . For example , when a man holds a ballance in his hand , with six pound in the one scale , and but one pound in the other , if you add another pound , the weight grows more , and the power and force of the opposite scale grows less proportionably ; not absolutely , for it still remains six pound , but respectively : that 's to say , six pound is less in respect of four , than in respect of five ; or the resistance of six pound is less , two counterpoising it , than being counterpoised by one . When a third is added , the weight grows yet more , and consequently the resistance of the opposite scale becomes yet less , till by adding the sixth and last pound , you augment and encrease the pondus to that same degree of strength , that the resistance of the opposite scale is of . From these considerations , I say , the surface of Air FG , hath not lost all its Pressure absolutely , by raising the Mercury from G to H , but only respectively , because it still retains 29 degrees of force in it self . I say respectively , because when the Mercury is raised ten inches , the power of the Air which is of 29 degrees of force , is less in respect of ten ounce , then in respect of five ; or the power of 29 degrees of force is less , being counterpoised by ten ounce , than being counterpoised only by five . And when it is raised 20 , it is yet less in this respect , than in respect of ten . And when it has raised the Mercury to the greatest altitude H , it may be said to have lost all its Pressure , seing it is not able , by vertue of a counterpoise , to do any more . Even as six pound in this scale , may be said to have lost all its resistance and weight , by putting in the other scale , first one pound , next two pound , and then three pound , till the last be put in , at which time it hath no more resistance . Though this be , yet it still remains six pound . Even so , the Air FG still remains of the same force and power , while it suspends the Mercury GH , that it was of before . Likewise , the Pillar AB , cannot be said to have lost all its pressure absolutely , by falling down from A to C , but only respectively , because the said Pillar CB , is still 29 ounce weight . I say respectively , because in falling down ten inches , or in losing ten ounce , the weight that 's now but 48 , is less , in respect of 29 , than while it was 58. It is yet less , when it hath fallen down other ten , because being now but 38 , it must be yet less in respect of 29 , than 48. And when it hath fallen down to C 29 , it may be said to have lost all its weight , because it can do no more , having respectively lost all its Pressure .

From what is said , we see a clear ground to distinguish in Fluids a pondus and a potentia . Secondly , that the potentia may sometimes exceed the pondus , and contrariwise the pondus may exceed the potentia . Thirdly , that inequality of weight , between the pondus and the potentia , is the cause of motion of Fluids . Fourthly , that the motion never ceaseth , till the pondus and the potentia become of equal force . This conclusion is not so universal as the rest , because the motion may sometimes cease , before this be . For example , when the Air is pressing Mercury up thorow a Tub shorter then 29 inches , the motion ends before there be a perfect counterpoise ; for 20 or 15 inches of Mercury , can never counterballance the force and power of the Air. In such a case then , there is an unequal Pressure , the Air pressing the Mercury more , than the Mercury doth the Air.

EXPERIMENT VIII . Figure 12.

TAke the Vessel ABCD , and fill it with Water , as high as HI . Take next a Cylinder of stone FG , and drowning the half of it among the Water , suspend it with a chord to the beam NO , with a ring at E. Now in this case , though the stone do not touch the bottom of the Vessel , yet the Water becomes heavier , than before . For discovering the true reason of this , I suppose fi●st , the weight of the Water , before the stone be drowned , to be 40 pound . I suppose next , that after the stone is drowned , the said Water to weigh 50 pound . And lastly , the stone to weigh 60 pound . I say then , the Water must be 10 pound heavier than before , because it supports 10 pound of the stone . 'T is certain the beam is less burdened by 10 pound than before . If this be , then surely the Water must sustain it . It were great temerity and rashness , to averr that neither the Beam , nor the Water sustains it , which is really to say , it is sustained by nothing . It cannot be said without ignorance , that 10 pound of the stone is evanished , and turned into a Chimera . If it be said , how can such a Fluid Body as Water , be able to support any part of the weight of the stone , that is such a heavy Body ? I answer , there is here no difficulty , for if the imaginary surface KL , upon which the 10 pound of the stone rests , be able to sustain 10 pound of Water ( I suppose the stone taken away , and the place of it filled with Water ) then surely it must also be able to sustain 10 pound of the heaviest metal ; seing ten pound of Lead , or Gold , or Stone , is no heavier than 10 pound of Water . If some say , this rather seems to be the reason , why the Water becomes heavier , after the stone is drowned , because it possesseth the place of as much Water , as would weigh 10 pound ; not ( as was said ) because the Water supports 10 pound of it . Therefore it may be judged , and thought , that if the space that the stone occupies , were filled with Air , or some light Body , without sensible weight , the Water would become heavier than before . For example , if in stead of the stone , there were placed a bladder full of wind , within the Water , and tied to the bottom with a string , that the surface might swell from HI to AB , the Water of the Vessel would become as much heavier than before , as is the bulk of Water , equal to the quantity of the bladder . Therefore , the Water becomes heavier , not because it supports any part of the stone , but because the stone occupies as much room and space , as would contain 10 pound of Water : for by this means the drowned stone raiseth the Water from HI to AB ; and so the Cylinders AC , and BD , being higher , press with greater weight upon the bottom CD , even with as much more weight , as if the space that the stone occupies were filled with Water .

For answer to this , we shall make this following Experiment . Take the Vessel MPVX , and fill it with Water to QR . Next , take a large bladder WY full of wind , and tying the neck with a threed , thrust it below the Water , and fasten it to the bottom , with a string , to the Ring Z. This done , the Water swells , and rises from QR , to MP . Now , if it be true , that the Water in the Vessel becomes heavier , not because it supports 10 pound weight of the stone , but because the stone occupies the room of 10 pound of Water ; then it ought to follow , that after the bladder is tyed below the Water , the said Water should become heavier , than before , even by three pound ; for I suppose a bulk of Water , equal to the bulk of the bladder , to weigh as much . And the reason is , because ( as you say ) the quantity of the bladder WY , makes the water swell from QR to MP , by which means the Pillars of Water MV , and PX becomes higher , and so presseth with greater weight upon the bottom VX . For clearing this difficulty , I say , when a bladder is thus below the Water , tyed to the bottom , the Water becomes not three pound heavier : for when you place the Vessel with the Water and bladder , in the Scale of a Ballance , the said Water weighs no more , than if it wanted the bladder : therefore the Water becomes not heavier , because the stone possesseth the room of 10 pound of Water , but because the Water sustains 10 pound of the stone . Now the reason , why the bladder makes not the water heavier , though it raise it from QR to MP , is this ; because though verily there be a greater Pressure then before , even upon the bottom of the Vessel , yet because moe parts are not added , the natural weight cannot be augmented , which essentially depends upon the addition of these parts . If it be replyed , the Experiment of the bladder is to no purpose , because it being knit to the bottom , pulls up the Vessel , with as great force , as the growth of the Pressure bears it down , and so the Bladder cannot make the Water heavier . But , if so be , it were possible , that the Bladder could remaine within the middle of the Water , without being knit to the bottom , and consequently without pulling up the Vessel , then surely the Pillars of Water MV , and PX , being higher , would press with greater weight upon the bottom , and so make the Vessel , and the Water weigh more in the ballance : for 't is to be supposed , that during all this time , this Vessel with the Water , is in one scale , and a great weight of stone or lead , in the other . So would the Water ABCD become heavier likewise , provided the space and room , that the stone fills among the Water , remained intire , after the stone is taken away : because that room and empty space remaining , would keep the surface , as high as AB , by which means , the Pillars AC and BD , being higher , would press with greater weight upon the bottom , and cause the Water weigh more in the ballance . I answer , though by some extraordinary power , the bladder could remain below the water , of its own accord , as it were , and though the space and room , by that same power , which is left by the stone , were keeped empty , yet shall they never be able to make the Water heavier . As to the reason , that 's brought , I answer , the rising and swelling of the Pillars , will make indeed a greater Pressure upon the bottom of the Vessel , but because this Pressure may be produced , and generated without the addition of new parts , therefore , it can never make the Water heavier : for if this were true , then it would follow , that the more a body is comprest , it should be the heavier , which is contrary to sense , and experience . This Pressure is like unto Bensil , that cannot weigh in a ballance , though the thing bended do weigh ; as a Bow that weighs so many pounds , but the Bensil of it weighs nothing : Next , will any man think , that a Cub of Water six foot high , and six foot thick , will weigh more in a ballance , then it did , after it is turned into a long square Pillar 216 inches high ? I grant , there is near 60 times a greater Pressure , upon the bottom of the Vessel , yet because this Pressure is generated , without the addition of new parts , it cannot make the Water heavier . Moreover , it is mechanically possible to keep the Water STVX , under that same degree of Pressure it hath , though the rest above were taken away : if this be , then it ought to be as heavy , as the whole , seing it still Presses the bottom , with that same degree of Pressure , it had from the whole : but what is more absurd , than to say , one part of Water , is as heavy , as the whole ? e. g. a pint as heavy as a gallon . If it be said , the Pressure , and the weight , are but one thing , at least effectively , which is sufficient to the purpose in hand , as is clear from the Theorem 23. I answer , they are but one thing indeed , in order to the Ballance of Nature , but they are neither formally , nor effectively the same thing in order to the Libra or Artificial Ballance , whereof we are now treating . I shall conclude with this ; while the Vessel with the Water , is thus placed in the Scale of the Ballance , and in equilibrio , with the opposite Scale , cut the string that tyes the bladder to the bottom , and when it comes above , you will find the Water , just of the same weight it was of : for though the surface MP , by taking out the bladder , settle down to QR , yet there 's no alteration made in the weight . From this I gather , that if the swelling of the Water should make it heavier , then the subsiding and falling down of it , ought to make it lighter .

From these Experiments we gather first , that in Water there is a Pressure , because it sustains 10 pound of the stone FG. Secondly , that whatever heavy body is weighed in Water , it loseth just as much of its weight , as the bulk of Water weighs , it puts out of its place . This is evident , because the stone is 10 pound lighter in Water , than in the Air , because the Water that would fill the room of the stone , is just of that weight . We see thirdly , that the Pressure of Water , and the natural weight of it , are two things really distinct ; because the Pressure may be augmented , without any increment of the natural weight . We see fourthly , that the Pressure , or Bensil of a Fluid , cannot affect the Scale of a Ballance , but only the natural weight . We see fifthly , that a body naturally heavier than Water , weighs in Water , because the stone FG , makes the Water about it , 10 pound heavier . If it be inquired , whether bodies , that are naturally lighter , will weigh in Water ? I answer , if they be of any sensible weight , they weigh , as well as the other . For this cause , I except Air. For though they were never so light , in respect of Water , yet if they have any considerable gravity with them , they will make the Water heavier , they are among . Put the case the Body were a Cube of Timber of six inches , weighing sixteen ounces , and that a Cube of Water of that quantity , weighed 112 ounces . Here 's a great inequality , between their natural weights : yet if that piece of Timber , were made to exist in the middle of Water , as the Bladder doth , it would make it 16 ounces heavier . The reason is this ; these 16 ounces are either supported by a surface of Water , or they support themselves . This last is impossible . If the Water support them , then must they make the said Water 16 ounces heavier . Note , that though a Body naturally lighter then Water , as Cork , may be said to weigh in Water , that 's to say , to make it heavier , in which sense Water weighs in Water , because if you add a pint to a gallon , it makes it heavier ; yet if you take a piece of Cork , and knit it to the Scale of a Ballance , by a threed , the Cork hanging among the Water , the Scale hanging above in the Air , it will not weigh in Water ; because in this sense , no Body weighs in Water , but that which is naturally heavier then Water , as Lead , or Stone . In this sense , Water doth not weigh in Water , as will be seen in the 17 Experiment .

EXPERIMENT IX . Figure 13.

Take a Glass-pipe 70 inches long or there-about , and of any wideness , having the upper end H , hermetically sealed , the lower end C compleatly open , and fill it with Mercury , and cause a Diver carry it down to the ground of the sea MN , where I suppose is standing the Vessel ABDE with stagnant Mercury , and drown the end below the surface AB . This being done , the Mercury falls from the upper end H , to the point G , and there halts ; the space HG being empty . For understanding this Experiment , I shall propose several questions , and answere them . First , what 's the reason , why the Mercury subsides , and sinks down from H to G ? I answer , as formerly in the like cases , inequality of weight between the Pondus of the impending Quick-silver , and the Potentia of the surface , of the stagnant Quick-silver DCE . For while the Tub is compleatly full , the weight is so great , that the surface DCE , is not able to sustain it , therefore it must fall down , seing motion necessarily followes in Fluids , upon inequality of weight . It may be inquired secondly , why it halts at G , 58 inches from AB , and comes no further down ? I answer it halts at G , because when it hath fallen down to that point , there happens equality of weight , between the suspended Pillar , and the foresaid surface : for whatever weight the said Pillar is of , the surface on which it rests , is of the same . In a word , the Pondus of the one , and the Potentia of the other are now equal . For understanding this , consider according to the 25 Theorem , that the weight of the Element of Air , upon the surfaces of waters , is equivalent to the burden of 34 foot of water , therefore the first and visible surface of this Water LIK , is really as much prest , with the burden of the Atmosphere , as if it had 34 foot of Water upon it . Consider next , that between the said surface , and the ground MN , are 34 foot of Water indeed . Consider thirdly , that a Pillar of Water 34 foot high , is exactly of the same weight , with a Pillar of Mercury 29 inches high ▪ for if Water be 14 times lighter than Mercury , then they cannot be of equal weight , unless the one be 14 times higher than the other . Now , supposing the weight of the Air upon the surface LIK , to be equivalent to 34 foot of Water , or ( which is the same thing ) to 29 inches of Mercury , the surface of the stagnant Mercury AB , must be as much burdened with the incumbing Water , and the Air together , as if it had really resting upon it , a Pillar of Mercury 58 inches high . If this be , then it follows by necessity , that there must be an equality of weight , between the pondus of the Mercury in the Tub , and the potentia of the surface DCE ; Or ( which is all one thing ) that the part C , on which the Pillar rests , is no more burdened , than the part D or E. For if 34 foot of Water , and 34 foot of Water , be equivalent for weight , to 58 inches of Mercury , then must the part D and E , be as much burdened with the said weight , as the part C is burdened with the Pillar within the Tub , seing both are of the same height : therefore the power , and force of the imaginary surface of the stagnant Mercury DCE , is of the same strength , with the weight of the Pillar GFB . And this lets us see the reason , why the whole 70 inches cannot be suspended ; for if the outward Pressure that 's upon AB , be but equivalent to the Pressure of 58 , it can never make the surface DCE able to support 70.

To make it evident ( if any doubt ) that the Mercury is suspended by the weight of the Water , and the weight of the Air superadded , let a Diver bring up this Engine to the top of the Water , and he will find the one half to have fallen down , namely from G to F , the other half FB remaining . And if it were possible , to convey this Experiment to the top of the Air , the Bearer would see , the remaining half to fall down likewise , and become level with AB ; for where no Pressure of Air is , there can be no Mercury suspended . This falling down , is not all at once , but by degrees , and keeps a proportion with the Pressure of the Air , that grows less and less , from the ground to the top .

From this Experiment we see first , the great Pressure and weight , the Elements of Air and Water are under , seing this Water , that 's but 34 foot deep , sustains the Mercury between G and F , 29 inches , as much between F and E , being kept up by the Pressure of the Air. We see secondly , that this Pressure is according to Arithmetical Progression , as 1 , 2 , 3 , 4 , 5. because in going down the first 14 inches , the Mercury rises one inch ; in going down the second 14 inches , it rises two ; in going down the third 14 inches , it rises three , and so forward . We see thirdly , though a Water were 100 fathom deep , yea 1000 , yet the Pressure of the Air above is found at the bottom : for supposing this Experiment were 100 fathom deep , yet would the Air from above have influence upon it , to sustain so many inches of the Mercurial Cylinder . A Diver then , 10 or 15 fathom under the Water , must be burdened with the weight of the Air , as well as with the weight of the Water , so must the Fishes , though never so deep . We see fourthly , that the parts of a Fluid cannot cease from motion , so long as there is an inequality of weight between the pondus and the potentia . This is clear from the falling down of the Mercury from H to G. And assoon as equality of weight happens , the motion ends . This is clear from the Mercurie's halting at G. Fifthly , that in Mercury , as well as in Water , or Air , surfaces may be distinguished , and that these surfaces , are endowed with a Potentia or power , begotten in them by superior and extrinsick weight . This is clear from the imaginary surface DCE , that 's made powerful to support 58 inches of Mercury in the Tub , and that by the weight and Pressure of the Air resting upon AB . Sixthly , that , as two Fluids differ in specifick and natural weight , so they differ in altitude , when they counterpoise one another . This is clear from the disproportion that 's between the altitude of the Mercury suspended , and the height of the Water , and Air suspending . GF then is 29 inches , and the deepness of the Water from K to N is 34 foot , because Water is naturally 14 times lighter than Mercury . FB is likewise 29 inches , and the hight of the Air , that rests upon the surface of Water is six or seven thousand fathom high ; because Air is 14000 times naturally lighter than Mercury . Seventhly , that Fluid Bodies counterpoise one another , not according to their thickness and breadth , but only according to their altitude . This is evident ; for though this Tub were never so wide or narrow , yet the altitude of the Mercury is unchangeable . Hence it is , that the thickest Pillar of Water in the Ocean , is not able to suspend more Mercury , than the slenderest , I mean as to altitude . And hence it is , that the smallest Cylinder of Mercury , no thicker than a silk threed , is able to counterpoise a Pillar of Water , of any thickness whatsoever . We may conclude lastly , that when a Diver is 20 fathom under the Water , he is under as much burden , as if he were under 14 or 15 foot of Quick-silver . Suppose a man lying on his belly , within a large Vessel , and 14 or 15 foot of Mercury poured in upon him , surely it may be thought , that such a burden were insupportable . But put the case , the Diver were down 40 fathom , then must the burden be doubled . This follows , because if a Pillar of Water 34 foot high , with the weight of the Air superadded , be as heavy , as 58 inches of Mercury , then surely a Pillar 20 fathom high , or 100 foot , must be as heavy as 170 inches , which is more than 14 foot .

EXPERIMENT X. Figure 14.

AGainst the former Experiment , there occurres some difficulties , which must be answered . As first , if it be the Pressure of the Water , that sustains the Mercury in the Tub ( see the 13. Figure ) then the weight of the said Mercury ought not to be found , while the Tub is poised between a mans Fingers . But so it is , that when a Diver grips the Tub about the middle , and raises it a little from the bottom of the Vessel , he not only finds the weight of the Tub it self , but the weight also of the 58 inches of Mercury that 's within it . But this ought not to be , if the said Mercury , be sustained by the outward Water . In a word , it ought not to be found , because the said Pillar of Mercury , as really stands , and rests upon the imaginary surface DCE , as a Cylinder of Brass or Stone , rests upon a plain Table of Timber or Stone . If then , it be supported by the said surface , why ought I to find the weight of it , when I lift up the Pipe a little from the bottom of the Vessel ? For clearing this difficulty , consider , that when the Mercury falls down from H to G , it leaves a sort of vacuity behind it , wherein there is neither Air nor Water . Consider secondly , that for this cause , there happens an unequal Pressure ; the top of the Tub without , being burdened with the Pillar of Water IH , which actually presseth it down , and nothing within between G and H , that may counterballance that downward Pressure . These things being considered , I answer to the difficulty and say , it is not the weight of the suspended Mercury that I find , but the weight of the Pillar of Water IH , that rests upon on the top of the Tub. If it be said , the Pressure of a Fluid is insensible , and cannot be found . I answer , it 's true , when the Pressure is equal and uniform , but not when the Pressure is unequal , as here . If it be asked , how comes it to pass , that the Pillar of Water IH , is exactly the weight of the 58 inches of Mercury ? I answer , besides the said Pillar , there is another of Air , that rests upon the top of it , which two together are exactly the weight of the suspended Mercury ; IH being of the same weight with the Mercury GF , and the foresaid Pillar of Air , being of the same weight with the Mercury FB . To make it more evident , remember that one inch of Mercury , is exactly the weight of 14 inches of Water ; and that one inch of Mercury , is of the same weight with 14000 inches of Air. If this be , then must the Pillar of Water IH , that 's 34 foot high , and of the same thickness with the 29 inches of Mercury GF , be of the same weight with it , seing 29 inches are to be found 14 times in 34 foot . For the same reason , is the Pillar of Air , namely SI , that rests upon the top of the Pillar of Water IH , of the same weight with the 29 inches of Mercury FB . For after a just reckoning , you will find , that 29 inches will be found 14000 times in the Pillar of Air , that rests upon the Pillar IH . Or in a word , the hight of the Air is 14000 times , 29 inches .

But here occurrs another difficulty . Let us suppose there were a Tub six foot high , one inch wide , having the sides , 3 inches thick . Imagine likewise the said Tub to be under the water 34 foot , with 58 inches of Mercury in it , as is represented in this 14 Figure . This being supposed , the Pillar of Water EAFCGD , must be far heavier , than the 58 inches of Mercury HB . The reason is clear , because the said Pillar , is not only 34 foot high , but as thick , as the Diameter of the Tub , whose sides are three inches thick . I answer , the whole weight of that Water EAFCGD is not found , while a man poises the Tub between his fingers , but only the weight of the part GA , which is exactly the weight of the Mercury HB . But here occurrs the great question , namely , why I find only the weight of the Water GA , and nothing of the weight of the Water , CE , or DE ? I answer , I cannot find the Pressure of the Water CE , because it is counterpoised with the upward Pressure of the Water IK . And for the same reason , I cannot find the weight of the Water DF , because it is counterpoised by LM ; but because there is nothing between H and A , to counterpoise the downward Pressure of the Water GA , therefore I find that . If it be objected , that the Water IK , cannot counterpoise the Water CE , because the one is farder down than the other , and consequently under a greater Pressure , than the other . I answer , though IK be stronger than CE , yet a compensation is made by the weight of the Tub. For understanding this , let us suppose the Water CE , and DF , to press downward with the weight of six pound , and the Water KI , and LM , to press upward with the weight of ten pound , there being four pound in difference . Suppose next , the Tub to weigh in the Air ten pound , and in the Water only six pound . If this be , then according to the eighth Experiment , and eighteenth Theorem , four pound weight of the Tub must rest upon the surface IL. And if this be , then must the Water IK , and LM , be four pound weaker with the Tub , than without it , and must only have six pound of upward Pressure .

Fig. 9 Pag. 5●

Fig. 10

Fig. 1● Pag. 7●

Fig. 13 Pag. 81

Fig. 14 Pag. 86

EXPERIMENT XI . Figure 15.

AMZC is a Water 15 foot deep . AB a Glass-tub 14 inches long , and full of Mercury . BC a Pillar of Water 13 foot , 10 inches high , thorow whose middle goes a string to the scale of the Ballance K , existing in the Air. DE is a Tub full of Mercury 28 inches long , with a Pillar of Water above it EF , 12 foot and eight inches . GH a Tub 42 inches long , with a Pillar of Water above it HI , 11 foot and six inches high . And lastly , ADGSM an imaginary surface , 15 foot deep . This Experiment is brought hither , to demonstrate that a heavy Body , weighs as much in Water , as in Air , which is point-blank to the common received opinion , and destructive of the 18 Theorem . To evince this , I must suppose the 14 inches of Mercury in the Tub AB to weigh 14 ounce ; and the 28 inches of Mercury DE , to weigh 28 ounce ; the 42 inches GH to weigh ( I mean in the Air ) 42 ounce . Now I say , to make a just equipondium between the two Scales K and L , there must be 14 ounce put into the Scale L. If after this manner you weigh the Tub and Mercury DE , 28 ounces will be required in the Scale L , and 42 , if you weigh the Tub and Mercury GH . For proving this Doctrine , I must appeal to Experience , which will not fail in this . If you reply , and say , upon supposition the Tub and Mercury GH , were a solid piece of brass , or iron thus suspended in the Water , ought it not to weigh less here than in the Air , even as much less , as is the weight of the quantity of Water , it puts out of its place : why then should not the Pipe HG , with the Mercury in it , do the same , seing there is no apparent difference between them , as to this ?

But to leave this , which will appear afterwards , and to let the Reader see the truth of the 18 Theorem , I affirm , 't is not the weight of the 14 ounces of Mercury AB , that burdens the scale of the Ballance K , and that makes a counterpoise with the 14 ounces of Stone , or Lead , that s in the scale L. What then is it , you say ? I answer , 't is 14 ounces of the Pillar of Water BC that does this . Neither doth the weight of the 28 ounces of Mercury DE burden the Ballance , but only 28 ounces of the Water EF. Neither doth the Ballance support the weight of the 42 ounces of Mercury GH , but it is only burdened with 42 ounces of the Water HI . The reason is most evident , because according to the Principles of the Hydrostaticks already laid down , the Cylinder of Mercury AB , within the Tub AB , rests immediatly upon the imaginary surface of the Water ADG , and therefore cannot burden the scale in any wise . The same is true of the other two Cylinders of Mercury . But in this I find small difficulty . The greater is , how to make it out , that the scale K , supports 14 ounces of the Water BC , and 28 of the Water EF , and 42 of the Water HI . To make this seem probable , consider first , as was noted , that this Water is 15 foot deep , and consequently the Pillar of Water BC , 13 foot 10 inches . The Water EF 12 foot eight inches . And HI , 11 foot and a half . Consider secondly , though this be true , yet we must count the Pillar of Water ZM 49 foot high . The reason is evident , because the Pressure of the Air , upon the surface of all Waters ( according to the 25 Theorem ) is equivalent to 34 foot of Water : this then being added to 15 , makes 49 , and by this reckoning the Water BC is 47 foot ten inches : the Water EF 46 foot eight inches : And lastly , the Water HI 45 foot six inches . Thirdly , for easie counting , I must suppose the whole Cylinder ZM to weigh 42 ounces , every 14 inches one ounce : and consequently the Water BC to weigh 41 ounces ; the Water EF to weigh 40 ounces ; the Water HI 39 ounces . Note , that in Physical demonstrations , 't is not needful to use Mathematical strictness in counting ; and so leaving out fractions , we shall onely use round numbers ▪ Consider fourthly , that in all Fluids , as hath been frequently marked , there is a pondus and potentia , the Water BC being the pondus , and the Mercury AB the potentia , the one striving to press down the Tub , the other striving to press it up . Consider fifthly , that by how much the more a Body suspended in a Fluid is pressed up , by so much the less the weight that presseth it down is found : and contrariwise , by how much the less it is pressed up , by so much the more the Pressure above is found . Consider sixthly , the less that a surface of Water is burdened , the more able it is counterballance the opposite Pressure , and the more it is burdened , it is the less able . Consider seventhly , that the Mercury AB , ( which is evident in all Fluids ) not only presseth downward , and burdens the surface ADG , but also presseth upward , and therefore actually endeavours to thrust up the Tub ; and so it is , that the Tub is pressed between two , namely between the Water CB , and the Mercury within it .

Now from these considerations I say , the scale K , must support , and bear up 14 ounce of the Water BC : for seing the Mercury is supported by the surface of Water on which it rests , it cannot by any means burden the ballance with its weight ; and seing it actually presseth up the Tub , ( according to the seventh consideration ) it must so much the more counterpoise ( according to the sixth ) the opposite Pressure of the Water BC , and consequently diminish the weight of it : so that the Ballance cannot support the whole , but a part . For according to what degrees of force , the Mercury presseth up the Tub with , according to the same , must the Pressure upon the top of the Tub be diminished , and so if the Mercury press up the Tub with the force of 27 ounce , the Water BC must press it down with 14 ounce only , and so the Cylinder BC , that weighs really 41 ounce , must press the top of this Tub only with 14 , which 14 ounce really counterpoiseth , the 14 ounce of Stone in the Scale L. But how is it made out , that the Mercury AB , presseth up with 27 ounce ? For understanding this , remember , that the Water is 49 foot high , taking in the Pressure of the Air , and that a Water of that deepness is able to support 41 inches of Mercury , every inch weighing one ounce . For if 14 of Water , be able to support one of Mercury , 49 foot , or 567 inches , must support 41. If then , the part of the surface A , be able to weigh 41 , it must have of upward Pressure 27 ounces , seing it's counterpoised de facto only with 14. Take notice , that in the Hydrostaticks , the word pressing , or weighing , as really and truly signifies a weighing up , as a weighing down , seing it is no less essential to Fluid Bodies to move upward , than downward , and that with equal force , and weight . According to this reasoning , the Ballance supports 28 ounces of the Water EF , ( Imagine the second Tub to be suspended as the first ) seing the Cylinder of Mercury DE , presseth up the Tub only with the weight of 12 ounce , which 28 ounce , really counterpoiseth the 28 ounce of Stone in the Scale L. But why doth the Mercury AB press up with 27 ounce , and the Mercury DE with 12 ? For answer , remember , ( according to the sixth consideration ) the shorter a Cylinder of Mercury is , the surface upon which it rests , is the stronger , and more able to press it up ; and contrariwise , the longer it is , the surface is the more unable and weak : therefore AB being shorter , and lighter than DE , the surface of Water must press it up with greater force : so that if the said surface AM , be able to press up the Mercury AB with 27 ounce , it must press up the Mercury DE only with 12 ounce . According to this rule , if the Mercury AB were 15 inches high , it would press up only with 26 ounce , if it were 16 , with 25 : if 17 , with 24 : if 18 , with 23 , and so forward . This leads us to a clear discovery of all the secrets here : for if the Mercury AB , thrust up the Pipe , with the weight of 27 ounce , then must the Scale K , be eased of so much weight , and so much must be subtracted from L. Now let us imagine the Pipe AB , to be empty both of Air , Water , and Mercury : in this case 41 ounce must be in the Scale L , to counterpoise it , seing the whole Cylinder BC , that weighs so much , does now really counterpoise it . Let us imagine next , these 14 inches of Mercury to rise , and fill the Tub AB : in this case , there happens a great alteration ; because the rising of them , are really equivalent to the subtracting of 27 ounce from the Scale L ; and the reason is , because by so rising and filling the Tub , they thrust up the said Tub , and by this means easeth the Scale K , of so much weight . Now this Scale being eased , you must of necessity take out from L 27 ounce for making a new counterpoise .

And lastly , the Scale K must support the whole weight of the Water HI , which is 39 ounce , nothing remaining to counterballance this downward Pressure , and consequently to ease the Ballance . How then is it counterpoised ? For clearing this , you must remember that this Water , that 's really 15 foot deep , must be reckoned ( as I said ) 49 , because of the Pressure of the Air upon the top , that 's equivalent to 34. If then it be so , it cannot raise Mercury higher in a Tub than 42 inches ; the one being 14 times heavier than the other : so that if 14 inches of Water , cannot raise Mercury higher than one inch , 49 foot cannot raise it higher , than 42 inches : for as 14 inches , are to one inch ; so is 49 foot to three foot and an half , which is 42 inches . Now I say , the whole weight of the Water HI , rests upon the top of the Tub , and so presseth down the Scale K , to which you must imagine this Tub , knit by a string , as the former was , nothing remaining to counterpoise this downward Pressure : for the top of the Mercurial Cylinder being raised as high within the Pipe , as the surface of Water DGS , is able to raise it , the said top can impress no force upon the Tub within , to thrust it up , and so to ease the Scale K. For example , when a man erects upon his hand a Cylinder of Timber , or any such like thing , which is the outmost he can support , he will not be able to impress any impulse , upon the seiling of a room above his head ; but if so be , in stead of that taken away , there be one lighter erected , which he is able to command , he can easily thrust up the seiling at his pleasure . Just so it is here ; for the 42 inches of Mercury , being the outmost , that the surface of Water DGS is able to bear , it cannot impress any impulse therewith upon the top of the Tub within : but easily can the Cylinder DE impress an impulse , and more easily the Cylinder AB , seing they are lighter , and so more powerful . To evidence this a little more , let us imagine two things , first , the Tub GH to be empty , as if vacuity were in it . In this case the top of the Tub ought to bear the whole burden of the Water , and consequently the Ballance to bear it also : because there is not a potentia within the Tub , to counterpoise this pondus . Next , let us imagine the Tub to be only full of Water : according to this supposition , the Ballance cannot be in the least part burdened ; because the Water within the Pipe , presseth it up with as much force , as the Water IH presseth it down : and if any thing should burden the Ballance , it would be only the weight of the Pipe , that 's not considerable .

From what is demonstrated , we see first , that though this Experiment would seem to prove at the first , that a heavy Body weighs as much in the Water , as it doth in the Air , because the whole weight of the Mercury AB is found in the scale L , yet 't is not so , because the 14 ounce of Stone L , doth not counterpoise any of the Mercury AB , but 14 ounce of the Pillar of Water BC. Secondly , there 's here a clear ground , for asserting a pondus and a potentia in Fluids ; because this Tub AB , is prest down with the Water BC , and prest up with the Mercury within it . Thirdly , there 's here a clear ground for asserting the Pressure of Water , even in its own place ; because the Water BC , counterpoises by it's weight , the 14 ounce of Stone L. Fourthly , we see an excellent way for finding the weight of any Cylinder of Water ; for whatever be the weight of the Mercury in the Tub , the Cylinder of Water , that rests upon the top , will be of the same weight exactly ; this is evident in comparing the weight of the Mercury GH , with the weight of the Water HI . Fifthly , that whatever be the height , and weight of a Pillar of Water , yet the Ballance can sustain no more of it , than the just weight of the Mercury : this is also evident , because the scale of the Ballance , supports no more of the weight of the Water BC , than the just weight of the Mercury AB . We see sixthly , the further down a Pipe with Mercury goes through Water , the greater is the Pressure it makes upon the top of the Tub within : for put the case , this were 100 foot deep , the Mercury GH , that wants all upward Pressure now , would press up the Tub with 40 ounce : the Mercury DE with 55 , and the Mercury AB with 70. We see seventhly , the shorter a Cylinder of Mercury be , it is the stronger in pressing ; and longer it be , it is the weaker ; for there 's more strength in AB , than in DE. We see eighthly , that the strength decayes , and grows , according to Arithmetical progression , as 1 , 2 , 3 , 4 ; because if you make the Cylinder GH 41 , that 's now 42 , it presseth up with one ounce . Make it 40 inches , it will press up with two ounces of weight . Make it 39 , it presseth up with three . And contrariwise , make the Cylinder DE 29 inches , that 's now but 28 , it will press up with 11 ounce only . ( With 28 it presseth up with 12. ) Make it 30 inches high , it will press up with 10. If it be 31 inches , it presseth up with nine , and so forward . Lastly , make the Cylinder AB 15 inches , that 's now but 14 , it presseth up with 26 ( with 14 , it presseth up with 27 ) make it 16 , it presseth up with 25 ; make it 17 , it presseth up with 24. We see ninthly , that in Fluids , we may make a distinction between a sustentation , and an equipondium . 'T is evident here , because there 's a perfect equipondium between the 42 inches of Mercury GH , and the outward Water that 's 49 foot deep . But 't is not so , between the said Water , and the Mercury DE ; because the said Water is able to raise the said Mercury 14 inches higher : therefore the Water only sustains the Mercury DE , but counterballances the Mercury GH . We see tenthly , that the pondus of the pillar of Water BC is counterpoised by two distinct powers really . The one is the 14 ounce of Stone in the scale L , the other is the 14 inches of Mercury AB , that as really thrusts up the Water , as the scale K pulls it up , by vertue of the opposite weight . Eleventhly , take away the Stone L , and you will find the Pipe with the Mercury AB sink down : this happens , not because the surface of Water on which it rests is not able to sustain it , but because the 14 ounce of the Water BC , that was supported by the Stone , doth now press it down . Twelfthly , the more a Body is unequally pressed by a Fluid , the more of the weight of that Fluid is sensible ; and the more equally a Body is pressed , the less sensible is the weight of that Fluid : this is evident , because there 's a greater weight of the Water HI found in the Ballance ( it takes 42 ounce to counterpoise it ) than of the Water EF , which is counterpoised with 28 ounce : and the reason is , because the top of the Tub H , supports the whole 39 ounce of Water HI , the Mercury within the Tub , not being able in the least to counterpoise it , or thrust it up . But because the Tub DE , is more equally pressed ( the Water EF presseth down with 40 , and the Mercury DE presseth up with 12 ) therefore less weight of the Water EF burdens the Ballance , only 28 ounce . Hence it is , that because the Tub AB , is more equally pressed , than either DE or GH , there 's less of the weight of the Water BC , found in the Ballance , only 14 ounce . Thirteenthly , if in the instant of time , while the Tubs are thus suspended in the Water , the Pressure of the Air above were taken away , and annihilated ; then first , the 42 inches of Mercury GH would fall down , to about 13 inches . Secondly , the 28 inches of Mercury DE , would fall down to as many . And lastly , the 14 AB , would sink down to the same height . The reason is , because the Pressure of the Air being equivalent to 34 foot of Water , no more would remain but 15 foot , which is the real height , according to ZM . But 15 foot of Water , cannot sustain moe inches of Mercury than about 13. And consequently , first , 14 ounce of Stone in the Ballance , would counterpoise the whole Water BC. The reason is , because the Water BC is but of 14 ounce ; and the Mercury AB , being but 13 inches high , could impress no impulse upon the top of the Tub within , that 's 14 inches high . Secondly , 13 ounce of Stone in the Scale L , would counterpoise the whole Water EF , seing EF is but 13 ounce . Thirdly , the same weight ( one ounce being deduced ) would counterpoise the Water HI , because in this case , it weighs but 12 ounce ,

To proceed a little further , imagine the Pipe GH to be suspended by the ballance , as the Pipe AB is ; and then a little hole opened in the top H , to suffer the Water to come in , till the Mercury subside 14 inches , namely from Q to O ( imagine this Tub to be the other ) and then stop it . The reason why the Water rusheth in , and presseth down the Mercury , is the force and Pressure of it : for the said Water , finding the Cylinder in equilibrio with the outward Water , presently by its own weight , casts the scales , which is easily done , seeing the surface GSM supports as much burden as it can . But that which is more considerable is this ; after the subsiding of the Mercury from Q to O ; the equilibrium that was between the scale of the ballance , and the Water QR is destroyed : for whereas 42 ounces were required before ; 29 will now do it . For understanding the reason of this , consider that between Q and O , are 14 inches of Water rushed in , which are equivalent to one inch of Mercury . Next , according to former reasonings , the ballance must support 29 ounces of the Water QR ; because in this case , the top of the Pipe within , is pressed up with the weight of 13 ounces ; which in effect , diminisheth as much of the downward Pressure of the Water RQ , which before had the burden of 39 ounces . But why is the Tub prest up with 13 ounces ? I answer , because the Mercury , that before was 42 inches , is now but 28 ▪ or having the 14 inches of Water QO above it , it is 29 , therefore being shorter , the surface GSM is the more able to Press it up , even with as much more force , as it is in inches shorter .

In the second place , let in as much Water more , as will depress the Mercury other 14 inches , namely from O to P. In this case , 16 ounce of stone will make an equipondium ; because , the 14 inches of Mercury PS , and the 28 inches of Water POQ , being a far lighter burden by 26 , than the 4● inches of Mercury , the surface GSM must be far abler to press them up now , than before : and therefore , must diminish as much of the downward Pressure of the Water QR , that burdens the Ballance , as themselves wants of weight : seing then , the whole Cylinder of Mercury , and Water together , are but equivalent for weight to 16 inches of Mercury , the top of the Tub within , must be prest up with 26 ounce ; and therefore they by their upward Pressure , must diminish 26 ounce of the weight of the Water RQ , that weighs 39. Lastly , let in so much Water , as will depress the last 14 inches PS ; and you will find no more weight required in the Ballance to make an equipondium , than counterpoiseth the simple weight of the Tub , which is not considerable . The reason is , because , the part S , of the surface GSM , being liberated of the burden of Mercury , and sustaining only the Water within the Tub , instead of it , this surface presseth up the Water within the Tub , and consequently the top of it , with as great force , and w●ight , as the top of the Tub without is depressed , with the outward Water RQ : therefore , 39 ounce depressing the Tub , and 39 ounce pressing it up , the Ballance must be freed of the whole weight of Water RQ . If it be objected , that the 42 inches of Water QS , are equivalent in weight to three inches of Mercury ; therefore the part of the surface S , being burdened with this , cannot press up , with as great force , as the Water RQ presseth down . For answer , consider , that the part S , is able to support 42 ounce of Water , and next , that the Water RQ weighs but 39. Then I say , seing the 42 inches of Water within the Tub , weighs only three ounce , the part S , that 's burdened therewith , being able to support 42 , it must press up with the weight of 39 , and so counterballance the Water RQ .

If it be inquired , whether or not , would the 14 inches of Mercury AB fall down , a small hole being made in the top of the Tub at B ? I answer , they would . If it be objected , that these 14 inches of Mercury , are not in equilibrio , with the Pressure of the ambient Water , as the Mercury GH , and therefore they cannot be so easily depressed by the Water , that comes in at the said hole . I answer , they must all fall down , and as easily , as the other , and that because of inequality of weight between the Potentia of the surface of Water , and the Pondus . It 's certain , the part A of the surface , cannot support more weight of any kind , than 42 ounce ; but when a hole is opened in B , and the Water comes in , 't is then burdened with the weight of 14 ounce of Mercury , and with the weight of 41 ounce of Water ; so much the Water BC weighs , which is 55 ounce : but a surface that hath only the Potentia of 42 , can never support a Pondus of 55 , no not of 43.

It may be objected thus : Put the case a Cylinder of Gold , or Brass were suspended in this Water ; as the Pipe and Mercury GH are suspended by the Ballance , would not the Ballance support the whole weight of it , without supporting any part of the weight of the Water IH , that rests upon the top of it . I answer , there 's a great difference between the two ; because a Cylinder of Gold or Brass , suffers both the upward and downward Pressure of the Water ; but the Mercury GH , suffers only the upward Pressure , being freed of the downward , by the top of the Tub. From this Experiment of letting in the Water upon the top of the Mercury , we see first , that when two Fluids are in equilibrio one with another , a very small weight will cast and turn the Scales , because , if the sixth part of an inch of Water come in at Q , it presently alters the hight of the Mercury from 42 inches to less . Secondly , 't is impossible for a surface of Water , to support more weight , than its own proper burden ; because the part S , cannot support more , no not a grain , than 42 ounce . We see thirdly , that it is as impossible for a surface of Water , to support less , than its own burden ; because whatever loss of weight the Pillar of Mercury SQ suffers , by the ingress of the Water QO , it s made up again by the same Water . If it be objected , that the 14 inches of Water QO , are not so heavy by far , as the 14 inches of Mercury , that fell down . I answer , its true , yet the part S , is as much burdened as before , because what is wanting in weight , it s made up , and compensed by Pressure . We see fourthly , that the Pressure of a Fluid is a thing really distinct from the natural weight , according to the 22 Theorem : because though the 14 inches of Water QO , are not so heavy naturally as the 14 inches of Mercury that fell down , yet the Pressure of them upon the surface S , is as much . We see fifthly , that 14 inches of Water , that 's a body fourteen times lighter than Mercury , may have as much weight with them , as 14 ounce of Mercury . We see sixthly , that a Cylinder of Mercury cannot be suspended in Air , or in Water unless it be guarded with a Tub , to preserve it from the downward Pressure of that Air or Water : for by opening an hole in Q , the Mercury subsides . We see seventhly , that 't is impossible for two Fluids to suspend one another mutually , unless there be a sort of equipondium between them ; because no sooner you destroy the equipondium , between the 42 inches of Mercury QS , and the part of the surface S , by the ingress of the Water QO , but assoon there ariseth a new one . We see eighthly ( as we noted before ) the nearer a Body comes to be equally pressed with a Fluid , the less is the Pressure of that Fluid sensible : because less weight is required in the Ballance , to counterpoise the Pressure , and weight of the Water RQ , after the ingress of the Water QOP , than after the ingress of the Water QO . We see ninthly , that when a Body is equally , and uniformly pressed with a Fluid , the Pressure is insensible ; because , after the Water hath thrust down all the Mercury from Q to S , there 's no more weight at all of the Water RQ found in the Ballance . We see tenthly , that not only in Water , the Pressure of Water may be found , but out of it , namely in the Air ; as is clear from the Ballance , that supports the Pressure of the Water RQ . We see eleventhly , a ground to distinguish between the natural Ballance , and the artificial Ballance . The artificial Ballance , is the Ballance KL : the natural , is the Pipe QS . We see twelfthly , that they keep a correspondence between themselves , or some Analogy : for by what proportion the Water thrusts down the Mercury , by that same proportion the pondus L , of the Ballance is lessened : and by what proportion the Mercury rises in the Pipe , by that same , is the weight L augmented in the Scale . We may subjoyn lastly , that the easiest way of explicating the Phenomena of Nature , is not always the best , and truest . For some may think , it were far easier to say , that the Ballance supports the Mercury AB , or DE , and not any part of the Water BC , or EF. But such a way would be false , and absurd , and contrary to all the former Doctrine .

EXPERIMENT XII . Figure 16.

THis Schematism represents a Water 100 foot deep , whose first and visible surface is IHK . And LM is the ground of it . CD is a piece of brass 30 inches high , and 12 inches in diameter , suspended upon the imaginary surface of Water ANB , which is distant from the top IHK , 25 foot . This Brass cannot go farder down , when demitted from H ; because it 's keeped up , by the Force and Pressure of the surface of Water ANB , which I prove thus . The part B sustains de facto , a Pillar of Water KB 1400 pound weight : therefore the part N is able to sustain as much . I suppose here , the said piece of Brass to weigh 1400 pound . The Water KB is 1400 pound , because its a Pillar 25 foot high , and 12 inches thick , for one cubical foot weighs 56 pound Trois . The connexion of the argument is evident , because it is as easie for a surface of Water , to sustain a solid Body , as to sustain a Fluid Body : therefore , if the part B , support the Fluid Pillar KB , the part N must be able to support likewise the solid Pillar CD , which is of the same weight . If it be objected , that the part N , sustains besides the Brass CD , a Pillar of Water EF 22 foot high , and a half , which two will weigh 2260 pound . I answer , upon supposition , that neither Water nor Air succeeded , the space EF being void of both , the Brass would be suspended with the force and power of the Water N. And though this cannot be made practicable , yet the Theory of it may conduce much for explicating the secrets and mysteries of the Hydrostaticks . But why ought the Brass to be suspended at 25 foot from the top ? I answer , because the potentia of the surface ANB , is equal to the pondus of the Brass . To evidence this , consider that Brass is a Body naturally heavier then Water , I shall suppose ten times , that 's to say , one inch of Brass will counterpoise ten inches of Water . If this inequality be , then must this Pillar of Brass go so much farder down , than the first surface IHK , as the one is heavier in specie , or naturally , than the other : therefore it must sink 25 foot exactly ; seing a piece of Brass 30 inches high , requires 400 inches of Water , or 25 foot to counterpoise it : for if one inch of Brass require ten inches of Water , then surely 30 inches must require 300. Yet it is no matter , what the thickness be , provided it be no higher than 30 inches .

To advance some farder , let us make a second supposition , namely , while the Brass is thus suspended upon the surface ANB , suppose the Air to come down , and fill up the imaginary space EF , then must the Brass be thrust down as far as the surface OP , that 's 34 foot below the surface AND , and 59 from the top . The reason of it is this , because the weight of the Air superadded , is equivalent to the Pressure of a Pillar of Mercury 29 inches high , and 12 inches thick : therefore the Brass being burdened with this , it must go so farder down , till it meet with a surface , whose potentia is equal in weight , to the pondus of both , which is precisely 59 foot from the top : for if one inch of Mercury require 14 of Water , then 29 inches must require 405 inches , or 34 foot . In a word , it must go as far down , as that surface , that sustains a Pillar of Water , that would counterpoise in a Ballance , the Brass CD , and a Pillar of Mercury 29 inches high , and 12 inches thick , both which weighs 3290 pound .

From what is said , we see first , that of two heavy bodies differing in weight , the lighter may go further down than the heavier . This is clear , because a slender Cylinder of Gold , in form of an Arrow , half an inch thick , and 28 inches long , weighing 28 pound ( 't is no matter , though the just weight of it be not determined ) will go down 35 foot in Water , before it meet with a surface , whose potentia is equal in weight to its own pondus ; for if Gold be 15 times heavier naturally than Water , then the said Cylinder must go down before it rest , 420 inches , or 35 foot . But a piece of Gold 12 inches long , and six inches thick , that perhaps will weigh 208 pound , will sink no further than 15 foot . And the reason is , because , if one inch of Gold require 15 of Water to counterpoise it , then 12 must only require 180 , or 15 foot . Note , that both the bodies must go down Perpendicularly , and not as it were Horizontally , with their sides downmost : for if they go down after this manner , they cannot sink so far . The reason of this is also evident , because a heavy body goes so far down , and no further , till it hath thrust as much Water out of its place , as will counterpoise it self in a Ballance . That 's to say , if an heavy body weigh 100 pound , it must go no further down , than after it hath thrust out 100 pound of Water . But so it is , that a piece of Gold , in form of an Arrow , going down side-wise , or with the two ends parallel to the Horizon , will thrust as much Water out of its place , as will be the weight of it self , before it can go down 15 or 16 inches from the top : because for every inch it goes down side-wise , it expells 28 inches of Water . In going down two inches , it expells 56. In going down three inches , it expells 84 , and so forward , till it go down 15 inches , where it expells 420 inches : but 420 inches amounts to 35 foot . Now , take a Cylinder of Water 35 foot high , and just the thickness of the Cylinder of Gold , which I supposed to be of half an inch , and put them in a ballance , and you will find the one just the weight of the other . Neither can the piece of Gold go so far down as before , if it go down side-wise ; because for every six inches it is drowned , it expells a bulk of Water 12 inches long , and six inches thick ; therefore it must be suspended , before it go beyond 90 inches , or seven foot and an half : now , if six inches give one foot , 90 inches will give 15 foot : but 15 of Water in hight , and six inches thick , is the just weight of it in a ballance , viz. 208 pound . We see secondly , the broader and larger the surface of a Fluid be , 't is the more able and strong to support an heavy burden : therefore the part of a surface of Water six inches square every way , will carry a far greater weight , than a part four inches square . Though a surface of Water 34 or 35 foot deep , be not able to sustain a Cylinder of Gold . if it exceed 28 or 29 inches in hight , yet take a Cylinder of Gold , 10 foot high , and reduce it , by making it thicker , to the hight of 20 inches , a surface of Water little more than 24 foot deep will sustain it . Or reduce a Cylinder 10 foot high , which requires a surface more than 100 foot deep , to a Cylinder six inches high , a surface little more than seven foot deep will support it . We see thirdly , the reason why bodies that are broad and large , move slowlier through Air and Water , than bodies that are more thin , and slender , though both be of the same weight in a ballance . For example , 20 pound of Lead , long and slender like an Arrow , will go sooner to the ground of a deep Water , than a piece of Lead of the same weight , in form of a Platter or Bason . The reason is , because as the body is broader , so it takes a broader part of a surface , which broader part is stronger and abler , than a narrower part , and so makes the greater resistance . The same is the reason , why a Bullet six inches in Diameter , moves slowlier thorow the Air , shot from a Cannon , than a Bullet one inch in Diameter . For the same reason , Ships of seven or eight hundred Tun , move far slowlier thorow the Air , and Water , than Vessels of less burden . Item , large and big Fowls , as Eagles , move slowlier , than small Birds , as Swallows . Yea , of Fowls of the same quantity , one may move quicklier than another , as is evident in long-wing'd Hawks , as Falcons , that by the sharpness of their Wings , move far more space in half an hour , than Kites , or Gose-Hawks , whose wings are rounder . We see fourthly , that there 's no body how heavy soever , but it may be supported by the surface of a Fluid , either in Air or in Water . I grant , the strongest surface of Air , that can be had , is not able to support more weight , than a Cylinder of Gold 28 inches high : yet though it were as large , and broad , as a Mill-stone , if it do not exceed the said hight , the Air is able to sustain it . For the same cause , if it were possible to free a Mill-stone of the Air , that rests upon it , the Air below would lift it from the ground , and carry it up many fathoms , even till it came to a surface , equal in power to the weight of the Stone . Or , if a large Mill-stone were demitted from the top of the Atmosphere , towards the Earth , it could hardly touch the ground , being detained by the way , by a surface counterpoising it . Or if it did touch , through the swiftness of the motion , it would surely , as it were , rebound , and be carried up again . It is alwayes to be remembred , that in such trials , the Air is supposed not to follow , or to be united , after the Stone passeth thorow . Now if the Air be able to do this , far more the Water , that 's a body a thousand times heavier . We see fifthly the reason , why heavy bodies move so easily thorow Air , and Water , namely because the parts that were divided , by the body that is moved , are presently reunited , and closed again , by which means it is driven forward , the Pressure upon the back , being as much as the Pressure before . If this were not , no body whatsoever would be able to move it self one foot forward . For example , if , when a man hath advanced one step forward , the Air did not close again upon his back , the force of the Air upon his belly and breast , would not only stop him , but violently thrust him backward . We see sixthly , the reason , why the same body descends with more difficulty thorow Water , than Air , because a surface of Water is far stronger , than a surface of Air. We see seventhly , that a heavy body is never suspended by a surface of Water , or Air , in going down , till once it hath displaced , as much Water or Air , as will counterpoise it self in a ballance . This is clear from the Brass CD , that goes alwayes down , till it expell its own weight of Water . For this cause , if a Mill-stone were demitted , or sent down from the top of the Air , and never rested , till it came within 40 fathom of the Earth , then so much Air , as is expelled by the descent , is the just weight of the stone . We see eighthly , the heavier a body be naturally , than Water , it goes the further down , and the lighter it is , it sinks the less . For if CD were of Gold , it would go further down , than being of Brass or Iron : and if CD were a stone , that 's lighter in specie than Brass , it would not go so far down . This lets us know the reason , why thicker , blacker , and heavier clouds comes nearer to the Earth , than thinner , whiter , and lighter . We see ninthly , that the Pressure of the Air is determinable , even in its heighest degree , and seemes to be the same in all places of the world ; but the Pressure of the Water is not so . The reason of the first part is , because the Element of Air seems to be of the same hight in all places , and therefore we may know its outmost Pressure , which is just equivalent to the weight of 28 or 29 inches of Gold , or Mercury . But because the deepness of the Sea is variable , therefore the Pressure is variable likewise . Yet if the exact deepness , of the deepest place were known , it were as easie to determine the greatest Pressure of it , as to determine the greatest Pressure of the Air. We see tenthly , that a very small weight added or subtracted in height , will change and alter the counterpoise of a Fluid . Because if you lay but one ounce upon the top of the brass at F , it presently subsides accordingly : or take one ounce from it , and it rises . But though never so much weight be added to it , or subtracted from it in thickness , no alteration follows . Therefore , though this piece of Brass CD , that 's now but 12 inches in thickness , were made 24 , by which means the weight would be tripled and more , yet the same surface ANB would sustain it : yet , add to it in altitude , but one inch , and presently it sinks down proportionably . This evidently discovers the reason , why it s as easie for the Air , to support a Cylinder of Mercury 3 inches thick , as to support a Cylinder half an inch thick : and why it cannot support more in height than 29 inches , and why it cannot support less . Now the reason , why a thicker Pillar , is as easily suspended , as a thinner , is this , because if a Pillar of Mercury be thicker , and consequently heavier , than i● takes a broader , and consequently a stronger surface of Air to ●est upon : if it be but slender , and so but light , then it takes a lesser part of a surface to bear it up , and consequently a weake● ; by which means the Pondus of the one , is alwayes proportionable to the Potentia of the other . Is it not as easie for a Pillar of stone , 6 foot in Diameter , to support another six foot in Diameter ; as it is for a Pillar one foot in Diameter , to support a Pillar one foot in Diameter ? But as a Pillar one foot in Diameter , cannot support a Pillar 6 foot in Diameter , neither can a surface of Air , one inch in Diameter , support a Pillar of Mercury 6 inches in Diameter . But why should a larger part of a surface be stronger than a narrower part ? I answer , the one is stronger than the other , for that same reason , why a thicker Cylinder is heavier than a thinner : for what I call strength in a surface , it s nothing else but weight , and what I call weight in a Cylinder , it s nothing else but strength . The same thing hath two names , because the pillar of a Fluid presseth down , and the surface supports : therefore , in the one it s called pondus , in the other potentia . As when two scales are in equilibrio , either this , or that may be called the pondus , or either this , or that , may be called the potentia . Now I say , if a part of a surface four inches broad , have as much weight or force in it , as a Pillar of Mercury four inches thick ; then surely , a part of a surface eight inches broad , must have as much weight and force in it , as a Pillar of Mercury eight inches thick . But why ought a surface to succumb , when the Pillar grows in hight , and not to fail when it grows only in breadth ? Ans. When it grows in breadth , the pondus never exceeds the potentia ; but when it becomes higher , then it becomes heavier . That 's to say , when a Pillar grows broader , there 's not one part of the surface that sustains it , more burdened than another ; seing the part eight inches broad , is no more prest with a Pillar eight inches thick ; than the part four inches broad , is prest with a Pillar four inches thick : as eight ounce of Lead in this Scale , is no more counterpoised with eight ounce in the other Scale , than four ounce in this Scale , is counterpoised with four in the other . But when a Cylinder grows in hight , the pondus exceeds the potentia ; one part of a surface being more burdened than another . We see eleventhly , that in a large surface of a Fluid , wherein are many parts ; each part is able to sustain its own proper burden . So a part eight inches in Diameter supports a Pillar eight inches thick ; and a part four inches , supports a Cylinder four inches thick ; but cannot support a Pillar six inches thick . But this seems rather to slow from the disproportion of Magnitudes , seing a circular plain 4 inches in diameter , cannot receive a Base of a Pillar 6 inches in diameter . But this is certain from the very nature of Fluids , that in a deep Water , wherein may be distinguished 100 , or 1000 different surfaces , each one is able to support his own burden , and no more .

EXPERIMENT XIII . Figure 17 , 18 , 19.

FOr making this Experiment , take two plain Bodies of Brass , or Marble well polished . Make them of any quantity ; but for this present use , let each of them be four inches broad square wise . Upon the back part , let each one have an handle about six inches long , of the same metal , formed with the plain it self , in the founding ( if they be of Brass ) as is represented in this Schematism . When they are thus prepared , anoint their inner-sides with Oyl or Water , and having thrust the one face alongst upon the other , with all the strength you have , till all the four edges agree , two whereof are represented by AB , and CD , you will find them cleave so closs together , as if they were but one Body . The effect is this , that ordinary strength will not pull them asunder ; and that under a surface of Water , a stronger pull is required than in the Air.

That we may deduce some Hydrostatical conclusions from this Experiment , let us suppose these two plain Bodies to be united in the middle of the Water IKPQ , that 's 34 foot deep , and suspended by a beam or long tree TV existing in the Air , near the top of the Water , by a chord SE passing between the middle of the beam , and the end of the handle at E. Suppose next a great weight of Lead R , 350 pound , to be appended to the end of the handle at H , of the under plain Body CDNO . This done , I affirm , that the beam TV , neither sustains the under plain Body CDNOGH , nor the 350 pound weight of Lead R , that hangs down from the handle GH . If it be objected , that the beam supports the upper plain Body ABLMFE ; therefore it must bear the weight also of the under plain CDNOGH , with the weight R ; seing they are both united together , and cleave so closs , as if they were but one Body . I answer , it supports the one unquestionably , but not the other . To explicate this Hydrostatical Mystery , I must aver three things ; first , that the inferior plain is supported by the upward Pressure of the lower Water PQNO . Secondly , that the burden which the beam sustains , is not the weight of the under plain , but the weight of the 34 foot of Water IKLM . Thirdly , that this weight is exactly the weight of the inferior plain , and Lead R. But is it not more easie to say , that the beam supports both the plains ? I answer , if I say so , I can neither affirm truth , nor speak consequentially , But may it not be said , that the inferior plain is supported both by the beam , and the lower water PQNO ? I answer , this is impossible ; because one and the same weight , cannot be supported totally , by two distinct supporters .

For making these assertions evident , I must suppose the superior Water IKLM to be 34 foot deep , and to weigh , if it were put into a ballance , 400 pound : and which is unquestionable , that the said Water rests upon the back of the superior plain LM . I suppose secondly , that the lower Water PQNO weighs as much , and thrusts up the inferior plain with as great weight , as the superior plain is prest down with , by the superior Water . This is evident from former Experiments . And lastly , I suppose each plain to weigh two pound , and the weight of Lead R 350. It is to be observed here , that no mistake may arise in the calculation afterwards , that though it be said , this 34 foot of Water weighs 400 pound , yet in it self it weighs but 200 : but considering the Pressure of the Air upon IK , which is as much , it may be truly said to weigh 400. These things being premitted , I say the weight that the beam TV sustains , is not the weight of the inferior plain , and the Lead R , but 352 pound of the superior Water IKLM , and consequently , that the inferior plain is supported by the lower Water PQNO . The reason is , because the lower Water presseth up with the weight of 48 pound . It is in it self 400 pound : but being burdened with 352 , it cannot thrust up with more weight than 48. Now , it pressing up with 48 , must ease the beam of 48 , and counterpoise so much of the superior Water , and consequently the beam must support only 352 pound of it . But put the case ( you say ) the weight R , were 130 pound , 160 pound , or 180 pound , would the beam be less or more burdened with the superior Water ? I answer , if R be 130 pound , then the beam supports only 132 pound of the superior Water ; for if the inferior be only burdened with 130 , the weight of R , and with two the weight of the inferior plain , then must it press up with 368 , and by this means , must ease the beam of so much , it sustaining 132 pound only . According to this compting , when the Lead R weighs 160 pound , the beam supports only 238 pound of the superior Water . If it weigh 180 pound , it sustains 218. And if the weight R were taken away , the beam supports no more of the superior Water than two pound .

To proceed a little further ; imagine the two Plains to be drawn up 17 foot nearer the first surface IK , namely as high as ZW . This done , the union breaks up , and they presently fall asunder . The reason is , because the surface ZW is not able to support 352 pound , but only 300 , which I prove thus . If 68 foot sustain 400 , then 51 foot must sustain 300. I say 68 , and not 34 , because as was noted , the Pressure of the Air upon the surface IK , is equivalent to other 34 foot : and therefore though the deepness of this Water , between IK and LM be but 34 foot really , yet it is 68 foot virtually , and in effect . Imagine secondly the surface IK to subside 17 foot , namely to ZW . In this case the union is broken also , and the lower Plain falls from the upper . The reason of this , is the same with the former ; because by what proportion you diminish the hight of the superior Water , by that same proportion you diminish the upward Pressure of the lower Water . Therefore , if you subtract from the superior Water 17 foot , that weighs 100 pound , you subtract likewise 100 pound from the inferior Water , and consequently , you make it press up only with 300 , but 300 is not able to counterpoise 352.

Let us suppose thirdly , the superior Plain , and the superior Water to be annihilated ; then I say , the Pressure and force of the under Water would thrust up the inferior Plain and the weight R about eight foot higher then XY and there suspend them . The reason is , because the surface XY , being able to sustain 400 , and being burdened only with 352 , must have the weight of 48. Now the upper Plain being taken away , and the upper Water also , and the empty space of both remaining , the said weight of 48 pound , must carry the under Plain as high as is said . Let us suppose fourthly , the Pressure of the Element of Air , that rests upon IK , to be taken away , then must the two Plain bodies be disunited , the inferior falling from the superior . The reason is , because in this case , the superior Water would have but the weight of 200 pound , and consequently the inferior , would press up only with as much : but 200 is not able to counterpoise 352.

From what is said we see first , that in all Fluids there is an upward Pressure , as well as a downward ; and that the one is alwayes of equal force to the other : because the inferior Plain is pressed up with as great force , as the superior Plain is pressed down with . We see secondly , that in Fluids , there is a Pondus and a Potentia . The Potentia here is the inferior Water , and the Pondus is the superior . Or , the 350 pound of Lead R , may be called the Pondus , which counterpoiseth the Potentia of the surface of Water XY . We see thirdly , that though the Pressure of a Fluid , be not the same thing with the natural weight , yet it is equivalent to it : because the 352 pound of Lead R , is sustained by the Pressure of the inferior Water , which could not be , unless they were virtually the same . We see fourthly , that there may be as much Pressure in one foot of Water , as there is weight in 100 , or in 1000 foot , or in 1000 fathom , For put the case , these two plain bodies were suspended , 100 fathom below the surface of the sea , and within a foot or two of the ground , as much weight would be required to pull them asunder , as is the weight of a Pillar of Water 100 fathom high , and 4 inches thick every way , which will be more then 3000 pound weight , besides the weight of the Air above , that will weigh 200 pound . This could not be , unless there were as much Pressure in the lowest foot of this Water , that 's 100 fathom deep , as there is weight in the whole Pillar above . We see fifthly , the more the potentia of a surface is burdened , the more sensible is the pondus : because the heavier you make the Lead R , that burdens the inferior Water , the more weight of the superior Water rests upon the Beam . We see sixthly , the more unequally a body is pressed , the more the Pressure is sensible . For understanding this , consider that the under-face of the superior Plain , is more and less pressed , according to the more and less weight the Lead R is of : for put the case , the inferior Plain were taken away , the face of the superior Plain , would be equally prest with the back of it . But when the inferior Plain is united to it , the Pressure of the Water is kept off ; by which means the back is prest more than the face . Now , as the inferior Plain becomes heavier and heavier , by making the weight R more and more weighty , the less and less is the face of the superior Plain prest up . Hence it is , that as this inequality of Pressure becomes greater and greater ; so the weight of the superior Water , affects the Beam more and more . Or , if the superior Plain were a sensible body , as Animals are , it would find the back of it more and more burdened , according as the weight R , becomes heavier and heavier . We see seventhly , that Water weighs in Water : because all the weight the Beam supports , is the burden of the superior Water , and not the burden of the inferior Plain , or of the weight R. It supports the weight also of the superior Plain , but this is not considerable . This is only to be understood , when the Pressure is unequal ; for if the upper Plain were as much prest up , as it 's prest down , the weight of the superior Water would not be found by the Beam . We see eighthly , that the higher a surface be , it is the weaker ; and the lower it be , it is the stronger : because when the two plain bodies are pulled up , 17 foot , they fall asunder . We see ninthly , the vanity of the common opinion , that maintains two plain bodies to cleave closs together for fear of vacuity ; and that neither Humane nor Angelick strength is able to break this union , without the rupture and fracture of them both .

It may be enquired , upon supposition , that the inferior plain had four holes cut thorow the middle , square-wise , as ABCD in the 18 Figure , what Phenomena would follow ? Before I answer , consider that this Figure represents the inner face of the Brass-plate CDNO , of the 17 Figure , which as was supposed , is four inches from side to side , and consequently contains 16 square inches . Now , imagine the under plain CDNO , while it is united to the uppermost , to have four square inches cutted out of it , as ABCD. These things being rightly conceived , and understood , I say , when the said holes are cutted thorow the beam TV , that now sustains 350 pound , shall by this means , only sustain 250 pound . To make this evident , consider that the under plain ( as was said ) contains 16 square inches . Next , that the top of the inferior Water upon which the plain rests , contains as many , and that every inch of the Water weighs 25 pound , seing the whole , as was supposed before , weighs 400 pound . Now , I say , the beam must support only 250 pound of the Water IKLM ; because , these holes being made , the top of the inferior Water comes through them , and presseth up the face of the superior plain with 100 pound , and so easeth the beam of so much . I affirm next , that though the inferior Water NOPQ be in it self 400 pound , and consequently able to support the inferior plain , with the weight R , albeit they weighed so much , yet the said holes being cut out , it is not able to support more burden than 300. The reason is , because of 16 parts that did actually bear up before , there are only 12 now that sustains . And every one of these twelve , being but able to support 25 pound , it necessarily follows , that the greatest weight they are able to sustain , is 300 pound . I affirm thirdly , that if a fifth hole were cut through , the under plain would fall from the upper ; because in this case , the inferior Water is not able to support 350 pound as before , seing of 16 parts , there are five wanting , and eleven remaining , cannot support more weight than 275 pound . Moe questions of this kind might be proposed ; as first , what would come to pass , if the the upper plain had as many holes cut through it , answering to the four of the nether ▪ Secondly , what would folow , if the nether plain were intire , and four bored through the upper ? But I shall supersede , and leave these to be gathered by the judicious Reader .

From this Experiment we see first , that the broader and larger a surface of a Fluid be , it 's the more able to sustain a burden , and the narrower it be , 't is the less able . Secondly , that each part of a surface , is able to sustain so much weight , and no more , and no less .

Before I put a close to this Experiment , it will be needful to answer an objection , proposed by Doctor More in his Antidote against Atheism , against the Pressure of the Air , which in effect militats , by parity of reason , against the Pressure of the Water likewise . He argues thus . If the Air were indowed with so much Pressure , as is commonly affirmed , then it ought to compress , squeez , or strain together , any soft body that it environs , as , v. g. Butter . Put the case then , there were a piece of Butter , four inches broad every way , and one inch thick , containing 16 square inches , upon every side ; as may be represented by the Figure 19. In this case , there is a far greater Pressure , upon the two faces , than upon the four edges ; and therefore , it ought to be comprest , and strained together , to the thinness of a sheet of Paper . For answer , let us suppose the piece of Butter , to be 30 or 40 foot below the surface of a Water , where it ought to suffer far more Pressure , than above in the Air. Next , that it lies Horizontal , with one face upward , and the other downward . Thirdly , that the upper face supports a Pillar of Water 200 pound weight , and consequently , that the under face is prest up with as much . And lastly , that every edge is burdened with 50. It may be represented , with the help of the fancy , in the 19 Figure , where AB is a piece of Butter four inches square , and one inch thick . Only take notice , that nothing here is represented to the sight , save one of the four edges , namely AB ; the other three , and the two faces being left to the fancy : Yet , the upper face may be represented by FHKM , and the under by NOPQ . These things being rightly understood , it is wondered , why the two great and heavy Pillars of Water , the one EGILFHKM , that presseth downward , and the other NOPQRSTV , that presseth upward , do not strain together the sides of the Butter ; seing the Pressure of the Water BC , and the Pressure of the Water DA , are far inferior to them for strength , even by as much difference , as four exceeds one . Though this objection seem somewhat , yet it is really nothing , which I make evident after this manner . First , I grant that the upper face FHKM is burdened , with 200 pound , and the nether face NOPQ with as much . Secondly , that the edge B , is only burdened , with 50 pound , as is the edge A. The other two edges , sustains each one , as much . Secondly , though this be , yet I affirm the two sides to be no more burdened , than the edges : that 's to say , the Pressure upon the sides , is equal to the Pressure upon the edges , which I prove thus . The Pressure upon the part M , is equal to the Pressure upon the part K , but the Pressure upon the edge B , is equal to the Pressure upon the part M : therefore the Pressure upon B , is equal to the Pressure upon K. The major Proposition is evident , because the Pillar of Water LM , is of the same weight , with the Pillar of Water IK . The Minor is also evident , because , the Pillar BC , is of the same weight , with the Pillar LM . Now , if the Pressure upon the edge B , be equal to the Pressure upon M and K , it must be likewise equal to the Pressure upon H and F. If this be , then the edge of the Butter B , must be no more prest , than the side FHKM : therefore the Water BC , can no more yeeld to the Water EFGHIKLM , and suffer the Butter to be squeezed out at B , than the Water LM , can yeeld to the Water EFGHIK , and suffer the Butter to be squeezed out at M. If any man shall insist and say , that the upper face bears the weight of four Pillars , which weighs 400 pound ; but the edge B is only burdened with 50 : therefore 50 ought to yeeld to 400. I answer , according to the 29 Theorem , namely , that a thicker Pillar of a Fluid is not able to press , or move a slenderer , unless there be an unequal Pressure , therefore the thick Pillar , that presseth the face , cannot move the slender Pillar , that presseth the edge : but there is here no unequal Pressure , seing the Water XYZV , is of the same hight with the four Pillars that rests upon the face of the Butter . I grant , if the said Water were not so high , as the other is , by the one half ; then surely the Butter would be squeezed out at B ; because the shorter a Pillar be , the less Pressure is in the surface under it ; therefore , there must be less Pressure , according to that supposition in the Water BC , then now is . Or put the case , the Pillar IK were shorter then GH , or LM , the same effect would follow , namely , a squeezing out of the Butter from K. Or , let us suppose the Pillar IK , to be higher than GH or LM . In such a case , the weight of the said Pillar would press through the Butter .

From what is said , we shall only inferr this conclusion , that equality of hight between Pillars of a Fluid makes equal Pressure , and inequality of hight makes unequal Pressure . Therefore 't is no matter , whether they be gross or small , thick or slender , provided they be all of the same Altitude .

Fig. 12 Pag. 81

Fig. 15 Pag. 100

Fig. 16 Pag. 109

Fig. 17 Pag. 119

EXPERIMENT XIV . Figure 20.

THis Schematism represents a Vessel full of Water 8 foot deep . EF is a Glass-Pipe , open at both ends , about 9 foot high , and one inch in Diameter . ABCD is a Vessel of Glass , or of any other metal , thorow whose orifice above , the said Pipe comes down . BHI is a Pipe going out from the said Vessel , crooked with a right angle at H , that the orifice I may look upwards . That some Hydrostatical conclusions may be inferred from this Experiment , fill the lower Vessel ABCD with Quick-silver almost ; then pour in as much Water above it , as will fill the space ABH , leaving from H to I full of Air. Next , thrust down the orifice of the Pipe E , below the said Water and Mercury , till it rest upon the bottom CD . Lastly , stop well with cement the passage of the lower Vessel , through which the Pipe came down , that neither Air nor Water may go out , or come in . These things being done , let down this Engine to the bottom of the large Vessel , which , as was noted , is full of Water from MN to KL , 8 foot , and you will find the Mercury to rise in the Pipe from AB to G , 6 inches , and more . The reason is , because there is a Pillar of Water KI , that enters the orifice I , and presseth down the Air , from I to P , 3 inches , which before was 6. This Air being so burdened ; instantly presseth forward the Water HBA : and this pressing the surface of the stagnant Mercury AB , causes the liquor run up the Pipe from AB to G , 6 inches : The reason , why it riseth 6 inches , is this : between the surface of the stagnant Mercury AB , and the top of the Water LOK , are 84 inches . Now Water being 14 times naturally lighter then Mercury , there must be 14 inches of Water , required for sustaining one inch of Mercury , and consequently 84 , for supporting 6. For a second trial , lift up the whole Engine to the top of the Water , and you will find the 6 inches of Mercury BG sink down , and become no higher within the Pipe , than the surface of the stagnant Mercury AB without . The reason is , because by coming up above the Water , the Pressure of the Water KI , is taken away from the orifice I , by which means the comprest Air HP , extending it self to I , liberats the Water ABH of the Pressure it had , and this freeth the Mercury of its Pressure , and so the 6 inches falls down . For a third trial , stop closely the orifice I , and let all down as before . In this case , you will find no ascent of Mercury from B to G : because the Water KI cannot have access to thrust down the Air from I to P , as formerly .

For a fourth , open the said orifice I , while the Engine is below the Water , and you will find the Mercury rise from B to G : because the Pillar of Water KI , hath now access to press . For a fifth trial , stop the orifice I , and bring up all to the top , and you will find the six inches of Mercury BG suspended , as if the Engine were under the Water . The reason is , because the stopping of the orifice , keeps the inclosed Air PH , under the same degree of Pressure it obtained from the Water KI . For a sixth proof , open the same orifice I , while the Engine is above the Water , and you will find the six inches of Mercury fall down , because the imprisoned Air HP , obtains now its liberty ; and expanding it self from H to I , eases the Water BH of the burden it was under . For a seventh , pour in 14 inches of Water at the orifice F , till it rest upon the top of the Mercury at G , and you will find one inch fall down . Pour in as much , and two inches falls down . In a word , pour in as much Water , as will fill the Pipe to O , and you will find the whole six inches fall down . The reason is , because the Water KI , is not able to sustain , both the six inches of Mercury and the Water , that 's poured in ; any one of them being able and sufficient to counterpoise it , For an eighth trial , empty the Pipe of the said Water , and after the Mercury is ascended from AB to G , as formerly , suck out the whole Air between G and F , and you will find the Mercury to rise from G to R 29 inches . The reason of this is evident from the Pillar of Air SK , that rests upon the top of the Pillar of Water KI : for by sucking out the said Air , you take away the pondus or weight , that counterpoised the weight of the Pillar SK , therefore it finding its counterpoise removed , presently causeth the Water KI , to enter farder within the crooked Pipe , till it hath prest up the liquor to R. For a ninth trial , take the six inches of Mercury BG , and put them into the scale of a ballance ; then take as much Water , as will fill the Tub between AB and O , and put it into the other scale , and you will find a most exact counterballance between them . The reason is , because if the Water KH , or a Pillar of that hight , be able to raise and counterpoise the Mercury BG ; then must as much Water , as fills the Pipe betwen B and O , be the just weight of it . The reason of this consequence is , because these two Waters are of the same weight : therefore , if the one be the just weight of it , the other must be so too . If it be said , that the Water , that fills the Pipe between B and O , is far thicker , then the Water KH ; therefore they cannot be both of one weight . I answer , equality of altitude , in this Ballance of Nature , is equality of weight : therefore , seing the one Water , is as high as the other , they must be both of one weight . If it be said , that a Pillar of Water between K and H , cannot counterpoise the six inches of Mercury BG , both being put into a ballance : and the reason is , because the one is thicker than the other . I answer , this only proves that two Pillars differing in weight in the Libra or Artificial Ballance , may be of one weight in the Natural Ballance : because in the Artificial Ballance , bodies counterpoise one another , according to all their dimensions , but in the Natural Ballance , such as this Engine is , Fluids counterpoise one another , according to their altitude only .

From the first trial , we conclude first , that Water even in its own place gravitats and weighs , because this Water by its Pressure , de facto thrusts up 6 inches of Mercury . We see in the next place , that the Pressure of a Fluid , is as easily communicated Horizontally , as Perpendicularly ; because the Pressure runs alongst from H to B. We see thirdly , that Fluids , may have as much Pressure begotten in them , even while they are environed about closely with solid bodies , whereby the superior Pressure , immediatly and directly by perpendicular lines is keeped off , as if they were immediatly under the Pressure : because the Mercury ABCD , is as much burdened with the Pressure , that comes from H , as if the upper part of the Vessel AB , were open to let in the superior Pressure , by perpendicular lines . The Air then under the roof of a house , is under as great a Bensil and Pressure , as the Air without , that 's directly under the Pressure of the Atmosphere . We see fourthly , that the Pressure of a Fluid , may be as easily communicated thorow the parts of Heterogeneous Fluids , as thorow the parts of Homogeneous ; because the Pressure of the Water KI , is as easily communicated thorow the Air PH , thorow the Water HB , and thorow the stagnant Mercury BD to the orifice E , as if nothing interveened but Water . We see fifthly , that Mercury can suffer a Pressure , as well as Water or Air ; because the six inches cannot rise from B to G , unless the stagnant Mercury ABCD were compressed , even in all the parts of it .

From the second trial , we see , that there cannot be a Pondus in a Fluid , unless there be a Potentia , to counterpoise it : for when you take away the Water RI , by lifting up the Engine to the top of the Water , the Mercury BG presently falls down . From the third trial , we conclude , that the Pressure of a Fluid , cannot be communicated thorow solid Bodies : for when the Engine is drowned below the Water , with the orifice I , stopped , no ascent of Mercury follows . We conclude from the fourth trial , that it is impossible for two Fluids to counterpoise one another , unless they be in Equilibrio ; because the Water KI cannot sustain the Mercury BG , unless it be of the same weight . From the fifth , we conclude , that a Fluid may be keeped under the same degree of compression , after the superior weight that begat it , is taken away : for after the Engine is brought above the Water , with the orifice I stopped , the Mercury BG is still suspended , even by vertue of the Pressure , that 's in the stagnant Mercury . This tells us , that a sphere of glass full of Air , may retain its Bensil , even though the whole Element of Air , that begat it , were destroyed . From the sixth we gather , that a Fluid cannot abide under Pressure , when the burden is taken away that begat it , or that keeped it under Pressure : for by opening the orifice I , the Air PH extends it self : and so are the Water , and Mercury within the Vessel freed of their Pressure likewise . We gather from the seventh trial , that in the Ballance of Nature , one Scale cannot be more burdened then another ; or that two Fluids cannot counterpoise one another , unless they be in equilibrio : for when you pour in 14 inches of Water , upon the top of the Mercury at G , they thrust down one inch , that there may be a just equipondium , between them , and the opposite weight KI . We gather from the eighth trial , which was observed before ; first , that there cannot be a Potentia in a Fluid , unless there be a Pondus to counterpoise it : for when you suck out the Air GO , which was the Pondus , that counterpoised the Air SK , this presently in stead of it , raiseth 29 inches of Mercury from G to R. We see secondly , that one pillar of Air can counterpoise another , Fluids of diverse kinds interveening : because the Air SK , counterpoises the Air within the Pipe GO , the Water KP first interveening ; the Air PH next interveening , and the stagnant , and suspended Mercury interveening also . We see thirdly from this eighth trial , that the Pressure of the Atmosphere , may be communicated thorow diverse kinds of Fluids , without the least diminution of its weight : because the weight of the Pillar of Air SK , is communicated , and sent down thorow the Water KI , thorow the Air PH , thorow the Water HB , thorow the stagnant Mercury BD , and up thorow the suspended Mercury BG , till it suspend the 29 inches between G and R , which is the just counterballance of it . We see moreover , that Fluids counterpoise one another , according to altitude only , and not according to thickness and breadth ; by comparing the Water KI , that 's but half an inch thick , to the Mercury BG , that 's a whole inch thick . We see from the last trial , that when a Fluid is necessitated , to counterpoise a Fluid of another kind , in stead of a Fluid of its own kind , it sustains no more of it , than what is the just weight of the Fluid of its own kind , because the Water KI , being under a necessity to counterpoise the Mercury BG , in stead of so much Water as would fill the Tub , it sustains no more of it , than the just weight of so much Water , as is said . We see secondly , that when two Fluids of divers kinds , do counterpoise one another , that which is heaviest in speciè , hath alwayes the shortest Cylinder . Next , that the difference between their altitudes , is most exactly according to the difference between their natural weights , therefore BG is 14 times lower than BO ; because Mercury is 14 times heavier than Water . We see moreover , that though two Cylinders of a Fluid , can counterpoise one another in the Natural Ballance , such as this Engine is , yet they will not do it in the Artificial Ballance : because though BG counterpoise KI in this Ballance , yet in a pair of Scales , the Mercury will be as heavy again as the Water . We see lastly , that notwithstanding of this , yet such a thing may be ; for if the orifice I , were made as wide as the orifice F , that the Cylinder KI might be equal to the Mercury BG in thickness , then surely the one would counterpoise the other in the Libra or Artificial Ballance .

EXPERIMENT XV. Figure 21.

THis Schematism represents a Water 72 foot deep , as CDAB , together with a crooked Pipe of glass INH , the one half whereof is IP , 56 inches high , and one inch wide , the other half is PNRH , of a far narrower diameter , with an orifice H. There is also an orifice at L , with a neck , about which is knit a small chord ML , for letting down this Engine to the bottom of the Water AB . For trials cause , fill the wide glass with Mercury from P to K , and you will find it rise in the narrow Pipe , as high as the orifice H. This being done , close hermetically , or with good cement the orifice L ; then by help of this chord , let all go down from the surface CD , till it be exactly 17 foot from the top , and you will find the Mercury thrust down in the narrow Pipe , from H to R , 14 inches and an half . Let it down next , as much , and the Mercury will be yet further thrust down , namely from R to N , the part HRN being full of Water . For understanding the reason of this , consider that between N and E , are 34 foot : for so high is the slender Pillar of Water , that comes from the top , and entring the orifice H , comes down thorow the Pipe to N. Consider next , that between the said Pillar of Water , and the Mercury NPK , there is a counterpoise : but this counterpoise cannot be , unless the Pillar of Water be 34 foot high , seing between N and K are 29 inches of Mercury ; for each inch thereof requires 14 of Water . Upon this account it is , that when the glass is 17 foot drowned , 14 inches and an half are thrust down from H to R. If it be objected , that the Pressure and Bensil of the inclosed Air IK ; is equivalent to the weight of other 29 inches ; and therefore the Pillar of Water EHRN , must be 68 foot high , before a counterpoise can happen . I answer , 't is true that 's said , but you do not consider , that there is a Pillar of Air FE , resting upon the top of the Pillar of Water , that makes a compensation exactly . To speak then truely and really , the 29 inches of Mercury NPK , have the weight of 58 inches ; and the 34 foot of Water EHRN , have the weight of 68 foot .

For a third trial , let down the glass 6 foot further , and you will find the Water pierce up thorow the thick Cylinder of Mercury PK , and rest upon the top K. The only difficulty is to determine , how much will spring up before the motion of it cease ? 'T is evident , that the Water will ascend , because coming to the Base of a thick and gross Cylinder , that it cannot intirely lift , it must pierce thorow it , seing the force of such a Pillar of Water , is now much stronger , than the Mercury : for in effect , the glass being drowned 6 foot further , the Pillar that comes down thorow the slender Pipe , hath the just weight of 34 inches of Mercury : but 29 cannot resist 34 : therefore the Water not being able to lift it , by reason of the disproportion that 's between the thickness of the one , and the slenderness of the other , it must pierce up thorow it . For clearing this difficulty , consider , that this glass cannot go down from one imaginary surface to another , v. g. from 34 foot , where it was , till it come to 40 , where it now stands , but there must be an alteration in the equipondium , seing by going down , the Pillar of Water EHRN grows h●gher , and consequently heavier ; and therefore , some Water must pierce up thorow the Mercury , for making a counterpoise ; for 't is impossible for two Fluids to counterpoise one another , unless they be in equilibrio . Consider secondly , that after the Water is come to the top of the Mercury at K , it will find difficulty to find a room for it self , seing the space between S and I is full of Air. Notwithstanding of this , it must ascend . I say then , after the glass is gone down from 34 , to 40 foot , there will be about four inches of Water above K , which have reduced the 29 inches of Air KI , to ●5 , SI.

If it be asked , between what two things is the equipondium now ? I answer , the first was at R , between EHR , and RNPK . The second was at R , between NRHE , and NPK . The third is now at S , between the 25 inches of inclosed Air IS , as one Antagonist , and the four inches of Water SK , with the 29 inches of Mercury KP , and the Water PNRHE , as the other . To make a fourth equipondium , sink the Glass other six foot , till it be 46 foot from the top CD , then must some more Water spring up thorow the Mercury ; this of necessity must be , seing the Cylinder of Water NRHE , is six foot higher , and so far heavier , than it was : if this be , then must the 25 inches of Air IS , be reduced to less quantity ; seing 't is impossible , for one Fluid to become heavier , unless its opposite and antagonist become heavier too , for an equipondiums sake . Note , that the Air IS , will not lose other four inches , with this six foot of Water , as it did with the former . The reason is , because , if for every six foot the Glass goeth down , the Air were comprest four inches , it were easie at last to reduce it to nothing : for if six reduce it to four , and 12 to eight , 38 ought to reduce it to no inches , which is impossible . Therefore I judge it must suffer compression , by a certain proportion , as we see upon a Scale , the divisions of Artificial or Natural Sines grow less and less , there being more space between 1 and 2 , than between 2 and 3 ; more between 2 and 3 , than between 3 and 4 , and so upward till you come to 90. Therefore the second six foot , must reduce the 25 inches , not to 21 , but to 23 circiter , and so forth . By the which means , though the Glass should go down in infinitum , yet the Air shall never be reduced to nothing , and there shall still some small quantity of Water come up . Or in such a case , the Air may be so comprest , that it can be no more , all the disseminate vacuities being expelled . But suppose this to be at 1000 fathom , then at 1500 , where the Pressure is stronger , there can be no equipondium , which is absurd , for where the pondus becomes stronger , the potentia ought to grow stronger likewise . I answer , the motion of condensation ceaseth indeed ; but there still remains a potentia , or rather in such a case , a perfect resistentia , whereby the Air is able to resist the greatest weight imaginable , before it can be reduced to nothing , or suffer a penetration of parts , that 's to say , two parts to be in one space .

From the explication of these Phenomena we conclude first , that in Water there is a considerable Pressure , seing in letting down the Glass 17 foot , the Mercury is prest down from H to R , and from R to N , in going down other 17 foot . Secondly , that 29 inches of Mercury are as heavy as 34 foot of Water : because the Mercury KPN makes a just equipondium with the Water EHRN . Thirdly , that Fluids not only of the same kind , but of different kinds , do counterpoise one another according to altitude , and not according to thickness ; because though the Mercury KPN be far thicker , than the Water EH , yet they counterballance one another , because a proportion is kept according to their altitudes . Fourthly , that a Fluid naturally lighter , may move a Fluid naturally heavier , and thrust it out of its own place , because the Water coming in at H , thrusts down the Mercury to R , and from R to N , and so forth . Fifthly , that of two Fluids unequal in strength , debating together , the weaker of necessity must yeeld to the stronger , though the weaker be far heavier naturally than the stronger , as is evident in the Mercury , that yeelds to the Water . Sixthly , that it is impossible for two Fluids , so long as they are unequal in strength , to cease from motion , till they come to an equipondium ; because the Water alwayes springs up thorow the Mercury , till an equal Ballance happen . Seventhly , that one Fluid of this kind , can counterpoise another Fluid of the same kind , though there be divers Fluids interveening : because the Air FE , counterpoiseth the Air IK , or IS , notwithstanding of Water and Mercury interveening . Eighthly , that there may be as much Pressure in one inch of a Fluid , as in a million ; because the 29 inches of Air IS , have as much Bensil in them , as is in the whole Pillar of Air EF , that goeth up from the top of the Water , to the top of the Atmosphere . Ninthly , that when one Fluid is under Pressure , the next must be under the same degree of Pressure , though they be not of the same kind , but of different sorts ; because the Air IS , the Water SK , and Mercury KP , are surely under the same degree of Pressure ; otherwise the motion could not end . Tenthly , that when two Fluids of divers kinds do press one another , that which is naturally lighter , ascends alwayes to the higher place , and the heavier to the lowest : because the Air IS , is above the Water SK , and the Water SK is above the Mercury . Note , that this is not universal , but only happens when the lighter Cylinder , is slenderer than the other , for if the Mercury KP , were no thicker than the Water PNRH , this would raise it intirely . Eleventhly , that the compression of Air to less space , is not according to Arithmetical progression , 1 , 2 , 3 , 4 , 5 , but according to some other proportion , which may be called Uniform-difform . Note here , that though this be true of the Air , while it is comprest from a more quantity to a less , as here , or in a Wind-Gun ; yet it is not true of the Pressure of the Element of Air , which is more and more from the top of the Atmosphere to the Earth , according to Arithmetical Progression , as in Water . We see lastly , that the heaviest of Fluids , such as Mercury , press upward , as well as downward ; because the top of the Mercury K , thrusts up the Water KS , as well as it thrusts down the Water PNRH . It may be enquired here , how far this Glass would go down , before the 29 inches of Air IK were reduced to one inch ? I answer , its hard to determine ; but it seems it ought to go down more than 300 fathom . In this case , there would be 28 inches of Water above K. Let us suppose the orifice H to be stopped at that deepness , and the Glass brought above the Water ; then , when the said orifice is opened in the Air , you will find the whole Water PNRH thrust out : and not only this , but the whole Mercury PK , spring out at the orifice H likewise , except a little that remains between N and H : the reason is , because the 29 inches of Air , being reduced to one , would be under a very great Bensil ; therefore the weight being taken away that begat it , of its own accord , it would expand it self to its old dimensions ; which it could not do , unless both the 28 inches of Water , that 's supposed to be above K , and the Mercury KP were thrust out of their places .

EXPERIMENT XVI . Figure 22.

THis Schematism represents a vessel full of Water 84 inches deep , namely from LN the first surface , to MR the bottom . From M to R in breadth are 20 inches . There are here also two Glass-Pipes open at both ends ; the one , two inches wide , the other half an inch wide . Both of them are 85 inches long . XYO is a surface of stagnant Mercury , among which the two ends of the Pipes are drowned . EC is a Pillar of Mercury six inches in height , and so is GD , both of them raised to that altitude , by the Pressure of the Water upon the surface XYO . The Pillar ECA is supported by , and rests upon , the imaginary Pillar AP. And so is the Pillar GDB , supported by the Pillar BQ . There are three things that occurres here from this operation of nature to be enquired after . First , why ought the Mercury to rise in the two Tubs , after the Vessel is filled with Water ? Secondly , why rather six inches , then seven or eight ? Thirdly , what 's the reason , why it rises as high in the wide Tub , as in the narrow ? I answer , the Mercury rises from C to E , and from D to G , by the Pressure of the Water , that rests upon the surface XYO . Before that the Water is poured into the Vessel , there is here a m●st equal and uniform Pressure upon the surface XYO , both without and within the Tub , namely from the Air that rests upon it . But no sooner is the Water poured in , but as soon the Pressure becomes unequal ; the parts of the surface without the Tub , being more burdened , then the parts C and D within . Therefore , the part that 's less prest , must rise and climb up , till the Pressure become equal : for it 's impossible that a Fluid can cease from motion , so long as there is inequality of weight between the pondus and the potentia . If any doubt , let him pierce the side of the Vessel , and when the whole Water is run out , he will find EC and GD to have fallen down , which clearly proves the climbing up of the Mercury , to depend upon the in-pouring of the Water . For understanding the reason of the second , remember that Mercury ( as we have often noted ) is counted 14 times heavier then Water ; therefore EC must be six inches , seing XYO is prest with the altitude of 84 inches of Water . It would be judged no marvel , to see the Mercury rise from C to E , and from D to G , provided the face of the stagnant Mercury were as high as ZF . No more strange it is , to see the two Mercuries rise , with the Pressure of the Water ; for in effect and really , the said Water is the just weight of as much Mercury as would fill between XO and ZF . For understanding the third , remember ( as was noted before ) that Fluid Bodies counterpoise one another , only according to altitude : therefore 't is no matter , whether the Tubs be wide or narrow . If it be enquired , how can one and the same Water , counterpoise two Fluids of different weights ? To say , that Fluids counterpoise one another according to altitude , doth not clear the difficulty ; for it still remains to be asked , why they counterpoise one another after this manner ? Therefore it seems , that if the Water raise the Mercury from C to E in the wide Pipe , it must raise it in the narrow one from D to K. For answer , consider first , that as there are here two Pillars of Mercury CE , and DG within the two Tubs , so there are here also two Pillars of Mercury AP and BQ , under the two orifices , upon which the said two Pillars stand , and rest . Consider secondly , that the Potentia or force of the Pillar AP , is just equal to the Pondus of the Pillar ECA : Item , that the Potentia of the Pillar BQ , is equal to the Pondus GDB . Thirdly , that the Potentia of AP ▪ is most exactly equal to the Potentia of BQ ; and the reason is , because their tops A and B , are parts of the same horizontal surface . I say then , if AP be equal to ECA , and BQ equal to GDB , and AP , and BQ , equal among themselves , then must ECA be equal to GDB . The same Water then , doth not counterpoise two Bodies of different weight . I grant ECA to be far heavier , than GDB , while they are weighed in a pair of scales , but the one is not heavier than the other , as they are weighed in this ballance of nature .

From what is said , we see first , that in Water there is a Pressure , and a considerable weight . This is evident from the rising of the Mercury . We see secondly , that Fluids counterpoise one another , only according to Altitude . Thirdly , that when a lighter Fluid presseth up a heavier , there is no more prest up of it , than is the just weight of the pressing Fluid , because the Mercury EC , is just the weight of the Water that presseth upon XYO . That 's to say , the part of the surface C , is no more prest with the Mercury EC , than the part X , is prest with the Water LZX . Fourthly , if Mercury were 28 times heavier than Water , only three inches would be prest up : if it were but seven times heavier , the altitude would be at S , 12 inches above C. Fifthly , it 's as easie for a large part of a surface , to sustain a large Pillar , as 't is for a narrow part , to sustain a narrower Pillar : because AP sustains ECA , as easily , as BQ sustains GDB . Sixthly , that in Fluids there is a pondus and a potentia : as is clear from the potentia of AP , that sustains the pondus of ECA . The Water likewise that sustains , hath a potentia , and the Mercury EC is the pondus of it . Seventhly , that there is alwayes equality of weight between the pondus and the potentia . So is the potentia of AP , equal to the pondus ECA . Eighthly , that the pondus begets the potentia . So the weight of the Water , begets the potentia that's in AP. For make this Water deeper , and you augment the potentia of AP. If you subtract from it , the potentia of AP grows less by proportion . Or the weight of ECA , may be said to beget the potentia of AP. To proceed a little further , let us suppose the Air HE to be removed . In this case , the Mercury rises 29 inches higher than E , or 35 above C ; even as high as S. In the narrow Tub it will climb up to K , if you take away the Air IG . This comes to pass , by vertue of the Pressure of the Atmosphere , that rests upon LN . From this we gather ninthly , that there is a counterpoise between the Air HE , and the weight of the Air that rests upon LN ; and that a slender Pillar of Air , is able to counterpoise a thicker : for HE is far narrower than LN . Tenthly , that the Pressure of the Air , can be communicated thorow divers kinds of Fluids ; because the weight that rests upon LN , is sent down thorow the Water LZX , and down thorow the stagnant Mercury , and thrusts up the Liquor from A to S , 35 inches . Eleventhly , that a lighter Fluid may be made to press with greater burden , than a Fluid naturally heavier ; because the weight of the Air upon LN , raises 29 inches of Mercury , but the Water raises only six . We see twelfthly , that Fluids have a sphere of activity , to which they are able to press up themselves , or Fluids of different kinds : because fi●st , the stagnant Mercury can raise it self no higher within the Pipe , than it is without . Next , the 84 inches of Water , can raise the Mercury no higher than E. Lastly , the weight of the Atmosphere , can raise the Mercury no higher than S , 29 inches above E.

For another trial , take out from among the Water , the two Pipes , and stopping closely the two under orifices , fill them with Mercury to the brim . Then thrust them down as before , and open the said two orifices , while they are below the surface XYO , and you will find the whole Cylinder fall down from H to E , and there halt : and the whole Cylinder in the narrow Pipe falls down from I to G. Or , if you please , before this be done , stop closely the orifice H , and the orifice I , and you will find the Mercury go no further down than S , by opening the orifice A ; and no further down than K , by opening the orifice B. This leads us to a clear discovery of the reason , why the Mercury subsides , and sinks down from the top of the Tub in the Baroscope , to the 29th inch , whatever the diameter of the Pipe be . And this lets us see , that the Mercurial Cylinder is suspended by the Air , after the same manner , that the Mercury EC is suspended after : and that there is no more difficulty in the one , than in the other .

EXPERIMENT XVII . Figure 23 , 24.

Fig. 18 Pag. 116

Fig. 19 Pag. 119

Fig. 20 Pag. 126

Fig. 21 Pag. 132

Fig. 22 Pag. 137

There are here several Phenomena to be considered . First , that the Water creeps in at the orifice G , and fills the under part of the Glass from M to K. Secondly , that not one particle of Air comes out , all the time the Water is in going in . Thirdly , that this Air is comprest from M to K , nine inches . Lastly , that the ingress of the Water , is according to unequal proportion : because while the Glass passeth from A to B , more Water creeps in at G , and fills the bottom , then in passing from B to C. And more in going down from B to G , than in going down from C to D , as is clear from the unequal divisions 1 , 2 , 3 , 4 , 5 , 6 , For understanding the reason of the first , remember that in this deep Water , there is a Pressure , and that this Pressure grows , as the Water grows in deepness . It is then by vertue of this , that the Water creeps in , and fills the bottom of the Vessel : for in effect , every part being under a burden , and being therefore desirous to liberat themselves from it , they take occasion to thrust in themselves , finding , as it were , more ease here , than without , the Air within the Glass , being under less Pressure , than the Water without . The second Phenomenon is caused by the straitness and narrowness of the hole G : for this entry being no wider , than the thickness of a Sack-Needle , the Air cannot go out , while the Water is coming in ; that is , the passage is so strait , that the one cannot go by the other . This leads us to the reason of the third , for if not one particle of Air go out , all the while the Glass is in going down , then surely , the Water filling between M and K , must compress the Air , and reduce it from twelve inches to three . But the greater difficulty is , why the ingress of the Water is according to unequal proportion . For understanding this , consider , that this inequality , is not caused by any unequal Pressure that 's in the Water ; for if this were true , then there ought to be less Pressure in the surface F , than in the surface E , and less in E , than in D , which is false and absurd . This inequality then , must flow from the nature of the Air it self , that naturally suffers compression after such a manner . 'T is evident from the compression of Air in Wind-guns ; for less force is required to compress the fi●st span , than to compress the second : or contrariwise , more strength is required , to compress the third span , than the second ; more to compress the fourth , than the third , and so forth . 'T is evident in all bodies endowed with Bensil , as in the Spring of a Watch , that requires more strength to bend it . in the end , than in the beginning .

For a second trial , pull up from the bottom of the Water the Glass LIH , and when it comes above , you will find nothing in it . The reason is , because the Vessel being open between T and S , the whole Water IH , falls down by degrees ; but in effect , is really thrust out , by the strong Bensil of the comprest Air IL , that now expands it self , when it finds the Glass go up thorow the Water , whose Pressure is less , and less from the bottom to the top ▪ but the contrary effect follows , when the other Glass is pulled up ; namely , the Water remains within the Glass , and the Air above it , is thrust out by degrees , as the Glass comes nearer to the top . For understanding the reason of this , consider first , that while the orifice G , is level with the lowest surface , where it now is ; that 's supposed to be 30 fathom deep , there is a real counterpoise between the inclosed Air GK , and the ambient Water without : for with what force the one strives to be in , with the same force the other endeavours to be out ; and because they are in equal terms , therefore the one cannot yeeld to the other . If you please to give the victory to the Water , then let the Glass go further down ▪ but if you desire the Air to overcome , then must the Glass be pulled up . Pull it then up from the place it is in , till it come to F , and you will find a considerable quantity of Air come out at G , and after 2 or 3 minuts of time , emerge and come to the top A , in form of round Bells , or Bubbles . The deepness and groseness of the Water thorow which the Bubbles come , makes their motion so slow . The reason of this eruption , must be less Pressure of Water in the surface F , than in the lowest G , from whence the Glass came . Suppose then , the lowest to have six degrees of Pressure , F to have five , E to have four , D three , C two , and B to have one : and supposing the inclosed Air KG , to be equal in force to the Pressure of the lowest fathom , it must then have six degrees of Bensil in it . Put the case then , that with six degrees of Bensil , it come to the surface F , that hath but five , it must surely break forth , and overcome the force and power of that surface : for 't is impossible that two Fluids can be unequal in force and power , but the strongest must overcome , and the weakest yeeld : therefore , when the orifice comes to F , the Air being stronger than the Water , breaks forth ; and as long doth this eruption continue , as inequality of power continues between the one and the other . In pulling up the Glass from F to E , other five fathom , more Air comes out . The reason is the same , namely less Pressure in E than in F : therefore , when the inclosed Air , that hath five degrees of Bensil , comes to E , that hath but four , it must overcome , and so long must it be victorious , till by expanding it self , it be reduced to the Bensil of four . In pulling up the Glass from E to D , more Air yet breaks out , because a surface of three degrees of Pressure , is not able to resist four degrees of Bensil . In passing from D to C , more Air comes yet out for the same reason , till in going up to the top , where there is no Pressure , no more Air breaks out .

'T is to be observed first , that the motion of the Air up thorow the Water is but slow , the medium being thick , and gross . Secondly , that if the Glass be pulled up quickly , from one surface to another , or contrariwise , let down quickly , it presently breaks in pieces . This comes to pass through the strong Bensil of the inclosed Air , that must have time to expand it self , otherwise it breaks out at the nearest : for it being of six degrees of Bensil , and coming quickly to a surface of five , there happens an unequal Pressure , the sides of the Glass being thrust out , with greater force , than they are thrust in with . But if so be , the Glass move slowly up , the inclosed Air gets time to thrust it self out by degrees , so that whatever surface the Glass comes to , there is little difference between the Pressure of the Water , and the Bensil of the Air. The reason why the Glass breaks in pieces , while it goes quickly down , is likewayes unequal Pressure upon the sides : for in passing quickly from a surface of five degrees , to a surface of six , the sides are prest in with greater force , than they are prest out with , and the reason is , because through the straitness of the hole G , the Water cannot win in soon enough , to make as much Pressure within , as there is without . 'T is to be observed thirdly ; that if the orifice G be stopped , before that the Glass be sent down , it will not go beyond three or four fathom , when it shall be broken in peices ; though the motion were never so slow : and this comes to pass , through the strong Pressure of the Water . Fourthly , the stronger the Glass be in the sides , it goes the further down without breaking : therefore a round Glass Bottle , will sink 20 or 30 fathom , before that it be broken with the Pressure of the Water . If a Vessel of iron were sent down , it ought to go much further . An empty Cask , or Hogshead , will not sink beyond seven or eight fathom , without breaking , or busting ; yet a Bladder full of wind , knit about the neck with a Pack-Threed , will go down 100 fathom , yea 1000 without bursting .

It may be here inquired , what sort of proportion is keeped by the unequal ingress of the Water ? I answer , it may be known after this manner . Let first down the Glass one fathom , and having pulled it up again , measure the deepness of the Water in the bottom , of it . Next , having poured out that Water , let it down two fathom , and pulling it up , measure the deepness , which you will find more , than afore . Do after this manner , the third time , and the fourth time , till you come to the lowest fathom , and you will find the true proportion .

From what is said we see first , that in Water there is a Pressure , because through the force and power of this Water , the 12 inches of Air that filled the Glass , are reduced to three . Secondly , that this Pressure growes , as the Water growes in deepness : because there is more Pressure in B , than in A , more in C , than in B ; and so downward . Thirdly , that when Air is comprest , by some extrinseck weight , the Bensil is intended , and grows stronger by unequal proportion , as is clear from the unequal divisions , 1 , 2 , 2 , 4 , 5 , 6. Fourthly , two Fluids cannot cease from motion , so long as the potentia of the one , is unequal to the pondus of the other : this is evident from the Water 's creeping in at G , all the while the Glass is in going down ; and from the Air 's coming out , all the while the Glass is in coming up . Fifthly , that no sooner two Fluids come to equality of weight , but as soon the motion ends : because , if the Glass halt at D , E or F , in the going down , upon which follows a counterpoise , then doth the creeping in of the Water cease . Sixthly , there may be as much Pressure in a small quantity of a Fluid , as in the greatest : because there is as much Bensil in the small portion of Air , included between K and G , as there is of Pressure , and weight , in this whole Water , that 's 30 fathom deep . Seventhly , that the Pressure of a Fluid , is a thing really distinct , from the natural weight : this is evident from the Pressure of the inclosed Air GK , that 's more and less , as the Pressure of the Water KM , is more and less , but the natural weight is still the same , seing the same quantity remains . Eighthly , one part of a Fluid , cannot be under Pressure , but the next adjacent , must be under the same degree of Pressure : this is also clear , because what ever degree of bensil the included Air KG is under , the Water KM is under the same . Therefore , when the one is under six , as in the lowest fathom , the other is under six likewise . And when the one is under five degrees of Pressure , as in the surface F , the other is under as much . Ninthly , Bensil and Pressure are equivalent to weight : because the Water KM , is as much burdened with the Bensil of that small portion of Air above it , as if it had a Pillar of Water 30 fathom high upon it . Tenthly , that the Pressure of Fluids , is most uniform and equal , and that two Fluids of different kinds , may press as uniformly , as if they were but one : this is evident from the sides of the Glass , that are not broken in pieces , by the strong Bensil of the inclosed Air , and heavy Pressure of the inclosed Water ; and this happens because the Pressure without , is as strong as the Pressure within . We see lastly , that Water does not weigh in Water , because when a man lets down this Glass by the chord , to the lowest surface , he finds not the weight of the Water KM , that 's within the Glass , but only the weight of the Lead Q. 'T is certain , he finds not the weight of the Water IH ; because it rests not upon the Glass within , but is sustained by ' its own surface , the mouth of the Glass being downward , and open . When I say Water does not weigh in Water ; the meaning is not , that Water wants weight or Pressure in it , but that this weight and Pressure is not found , as the weight and Pressure of other bodies are found , while they are weighed in Water . For example , a piece of Lead or Gold , hung in the Water by a string , the other end being fastened to a Ballance in the Air , gravitats , and weighs down the Scale ; and the reason is , because Lead and Gold , are naturally and specifically heavier than Water ; but a piece of Metal of the same specifick weight with Water , or Water it self , cannot gravitat in Water , or weigh down the Scale of a Ballance ; and the reason is , because the surface of Water upon which they rest , bears them up with as great weight and force , as they press down with . If it be said , that the Water KM , rests upon the bottom of the Glass within ; and therefore , if the man above , find the weight of the Glass , he must find the weight of the Water within it . I answer , the consequence is bad , because the weight of the Water within , is sustained , and counterpoised by the weight of the Water without , whereupon the bottom of the Glass rests . That 's to say , as there is a Pillar of Water KM within the Glass , that presseth down the bottom , so there is a Pillar of Water without the Glass , whereupon the bottom of the Glass rests , and which bears up both . But the greater difficulty is this , the further down the Glass goes , it grows the heavier , because of more and more Water , that creeps in at G. Now 't is certain , the weight Q grows not heavier , therefore it must be the Water within the Glass , that makes the increase of the weight ; and therefore Water must still weigh in Water . If this argument had any strength in it , it would prove the weight of the Water IH to gravitat and weigh likewise ; because the further down this glass goes , it grows the heavier , because of more , and more Water , that creeps up from H to I. Now 't is certain , the weight of Lead B grows not heavier . Behold , the difficulty is the same in both , and yet it were rashness to affirm the Water IH to be found by a mans hand , when he pulls up the Glass with a string , seing it is sustained by its own surface , and not by any part of the Glass . Though this might suffice for an answer , yet because the contrary is mantained by some , and that with a new Experiment to prove it , I shall be at some more pains to vindicat the truth of what I have said .

This new Experiment to prove that Water weighs in Water , I found in a Philosophical Transaction , of August 16. Anno 1669. Numb. 50 , the Invention whereof is attributed by the publisher , to that honorable and worthy Person Mr. Boyl , whose conclusions and trials , I never much called in question , but finding this opposite , and contrary to what I have demonstrated , I shall crave liberty to say , amicus Socrates , amicus Plato , sed magis amica veritas ; and shall therefore examine it as briefly as may be . The words of the Publisher are as follows .

The Author of this Invention is the Noble Robert Boyl ; who was pleased to comply with our desires , of communicating it in English to the curious in England , as by inserting the same in the Latine Translation of his Hydrostatical Paradoxes , he hath gratified the Ingenious abroad . And it will doubtless be the more welcome , for as much as no body , we know of , hath so much as attempted to determine , how much Water may weigh in Water ; and possibly , if such a Problem had been proposed , it would have been judged impracticable .

The Method or Expedient , he made use of , to perform it , as near as he could , may easily be learned by the ensuing accompt of a Trial or two , he made for that purpose , which among his Notes he caused to be registred in the following words .

A Glass-bubble of about the bigness of a Pullets egg , was purposely blown at the flame of a Lamp , with a somewhat long stem turned up at the end , that it might the more conveniently be broken off . This Bubble being well heated to rarify the Air , and thereby drive out a good part of it , was nimbly sealed at the end , and by the help of the Figure of the stem , was by a convenient Weight of Lead depressed under Water , the Lead and Glass being tyed by a string to a Scale of a good Ballance , in whose other there was put so much weight , as sufficed to counterpoise the Bubble , as it hung freely in the midst of the Water . Then with a long Iron Forceps , I carefully broke off the seal'd end of the Bubble under Water , so as no Bubble of Air appear'd to emerge or escape through the Water , but the Liquor by the weight of the Atmosphere , sprung into the un-replenish'd part of the Glass-Bubble , and fill'd the whole cavity about half full ; and presently , as I foretold , the Bubble subsided , and made the Scale 't was fastned to , preponderate so much , that there needed 4 drachms , and 38 grains to reduce the Ballance to an equilibrium . Then taking out the Bubble with the Water in it , we did , by the help of a flame of a Candle , warily applyed , drive out the Water ( which otherwise is not easily excluded at a very narrow stem ) into a Glass counterpoised before ; and we found it , as we expected , to weigh about four drachms and 30 grains , besides some little that remained in the Egg , and some small matter that might have been rarified into vapors , which added to the piece of Glass that was broken off under Water and lost there , might very well amount to 7 or 8 grains . By which it appears not only , that Water hath some weight in Water , but that it weighs very near , or altogether as much in Water , as the self same portion of Liquor would weigh in the Air.

The same day we repeated the Experiment with another sealed Bubble , larger then the former ( being as big as a great Hens-egg ) and having broken this under Water , it grew heavier by 7. drachms and 34 grains ; and having taken out the Bubble , and driven out the Water into a counterpois'd Glass , we found the transvasated Liquor to amount to the same weight , abating 6 or 7 grains , which it might well have lost upon such accompts , as have been newly mentioned . Thus he .

Figure 24.

THe design then of this Experiment is to prove that Water weighs in Water ; but , it seems , there is here a very great mistake , which I shall make out after this manner . For which cause , let this Schematism 24 represent the Experiment already described . The Glass-bubble then is EPFR . The stem is HC : the weight that sinks the Glass is B. The surface of Water under which it is drowned , is AD. The Ballance to which the Glass is knit by a string is NO . And lastly EFR is the Water that came in , and filled the half of the Bubble . Now I say , it is not the weight of the Water EFR , that turnes the Scales above , and makes an alteration in the Ballance , but ' its only the weight of the Lead B , that does it . For evincing this , consider that all heavy bodies , are either lighter in specie than Water ; as cork , or of the same specifick weight with it , as some Wood is , or lastly heavier in specie than Water , as Lead or Gold . Now 't is certain , that bodies of the first sort cannot weigh in Water , and the reason is , because they being naturally lighter , their whole weight is supported by the Water , and therefore not one part of them , can be born up by a Ballance above . A piece of Cork that weighs 12 ounces in the Air , weighs nothing in Water , because as soon as it toucheth the surface , the whole weight of it is supported , and therefore cannot affect the Ballance above . But bodies of the third sort , as is clear from experience and reason , does really weigh in Water : And the reason is , because they being naturally heavier than water , their whole weight cannot be supported by it , and therefore some part of them must burden the Ballance , to which the body is knit . A piece of Lead , that weighs 12 ounces in the Air , will not lose above 2 ounces , when ' its weighed in Water ; or may be less . But here there is no difficulty . The question then is , in order to bodies of the same specifick weight with Water , as some Wood is , or as Water is . I say of such also , that they cannot weigh in Water ; and the reason is , because they being ●ust of the same weight , must have their whole weight supported by it ; even as one foot of Water , supports the whole weight of the foot above it . It may be evidenced after this manner . Take a piece of Wood , that 's lighter in specie than Water , and add weight to it by degrees , till it become of the same weight with Water . Knit it with a string to a Ballance , ond weigh it in Water , and you will find the whole weight supported by the Water . And the reason is , because , being left to it self , it can go no further down , than till the upper part of it , be level with the surface of the Water . Now , the whole weight being thus supported , not one ounce of it can burden the Ballance . In a word , the Ballance can never be burdened , unless the body that 's knit to it , have an inclination to go to the ground , when left to it self , which a body of the same weight with Water can never have . I conclude then , if a body of the same weight with Water , cannot weigh in Water , neither can Water weigh in Water , seing Water is of the same weight with Water . And Therefore the Water EFR , that 's now within the Bubble , cannot in anywise burden the Ballance above ; but must be supported wholly by the Water IKGH , upon which the bottom of the Glass rests . If it be said , that the Glass it self is supported by the Ballance , because ' it s heavier in specie than Water ; therefore the Water within that rests upon the sides of it , must be supported likewise by it . I answer , the whole weight of the Glass is not supported , by the Ballance , but only a part ; the Water IKGH supporting the other part . And this part is just as much as is the weight of Water , that 's expelled by the Glass . Now , if the said Water support so much of the Glass , because it is the just weight of so much Water , why should it not also , support the Water within the Glass ? Seing the Water within the Glass , is just the weight of as much Water , as will fill the space EFR .

I come in the next place to shew , that it is the weight of the Lead B that turns the Scales , when the Water comes in at C , and fills the half of the sphere . For understanding this , let us suppose first , the weight that 's in the Scale O to weigh six ounces . Secondly , that the Glass takes 12 ounces to sink it compleatly under the surface AD. Thirdly , the weight B to be 18 ounces ; namely for this cause , first , that 12 of it may sink the Glass ; next , that the other six may counterpoise the six in the Scale O. Lastly , that the Water within the Glass weighs six ounces . I abstract from the weight of the Glass it self , which is not considerable , seing the most part of it , is suppo●ted by the Water , and not by the Ballance . Now , I say , 't is six ounces of the weight B that makes this alteration , and turnes the Scales . For if 12 ounces sink the Glass below the Water , when ' its full of Air , and no Water in it , then surely six are sufficient to sink it , when it is half full . And the reason is , because there is a less Potentia or force in six inches of Air , by the one half , to counterpoise a weight of 12 ounces , than in 12 inches of Air. Therefore this Air , being reduced from 12 inches to six , it must take only six ounces to sink it . If this be , then the other six ounces that now wants a party to counterpoise them , must burden the Ballance , and be supported by the Scale : and therefore , to make a new equipondium again , you must make the weight O 12 ounces , by adding six to it , that it may counterpoise 12 of B , the other six being counterpoised by the Air EPF . Let us suppose next , this Glass to be compleatly full of Water , and the whole Air expelled . In this case the Scale O , must have 18 ounces in it , for making a new equipondium . The reason is , because there being no Air in the Glass to counterpoise any part of B , the whole weight of it must be sustained by the Ballance , and therefore in the Scale O , there must be 18. Now , I enquire , whether these 18 ounces , are the equipondium of the Water within the Glass , or of the weight of Lead B ? 'T is impossible it can counterpoise them both , seing the Water is now 12 , and B 18. It must then either be the counterballance of the Water , or the counterballance of the Lead . It cannot be the first , because 12 cannot be in equipondio with 18 , It must then be the second . Or if these 18 ounces in the Scale O , be the counterpoise of the Water within the Glass , I enquire what sustains the weight of the Lead B ? The weight of it , cannot be sustained by the Water , because 't is a body naturally heavier than Water , it must therefore be sustained by the Ballance , I conclude then , that Water cannot weigh in Water . If it be objected , that this conclusion seems to contradict , and oppose the Pressure of the Water , that 's been hitherto confirmed with so many Experiments . I answer , the Pressure of the Water is one thing , and Water to weigh in Water is another . The first is , when one Pillar of Water counterpoises another , or when a Pillar of Water counterpoises a Pillar of Mercury , or is counterpoised by a Pillar of Air , all which is in order to the Natural Ballance , wherein bodies weigh only according to altitude . The second is , when Water is not counterpoised by Water , or by Mercury , or by Air , or by any other Fluid ; but when ' its weighed by a piece of Lead or stone in an Artificial Ballance , for knowing how many ounces or pounds it is of , as if a man should endeavour to weigh the Water EFR by help of the Ballance above , which in effect is impossible .

EXPERIMENT XVIII . Figure 25.

MAke a Wooden Ark after this following manner . The Planks must be of Oak , an inch thick . The height 40 inches . The breadth 36. Closs on all sides , and above , and open below . And because the form is four-square , there must be four Standarts of Timber , in each corner one , to which the Planks must be nailed . Four likewise upon the top , crossing the other four at right angles , to which the cover must be joyned . The sides must be plained , and the edges both plained and gripped in all the parts , that the joynings m●y be closs . Upon the top fasten a strong Iron Ring , as at N , through which must be fastned a Rope , of so many foot or fathom . And because the use of this Engine is for Diving under the Water , it must therefore be all covered over with Pitch within and without , especially in the couplings . And because this Instrument cannot sink of its own accord , it must have a great weight of Lead appended to it , for that cause , whereupon the Divers feet must stand , while he is in going down . The precise quantity and weight of it cannot be determined ; because it depends upon the quantity of the Ark , which if large , requires a great weight : if of a lesser size , requires a lesser weight . But whatever the dimensions of the Ark may be , the weight of the Leaden-foot-stool can easily be found out by trial . This Invention then , is for Diving , a most excellent Art , for lifting up of Guns , Ships , or any other things , that are drowned below the Water . And it is in imitation of the Diving bell , already found out , and made use of with success . It is called a Bell , because of the form , that represents a Church-bell indeed , being round , wide below , and narrower in the top : only , the matter is of Lead . It seems , it is of this mettal , first , because Lead is weighty , and will therefore easily sink : secondly , because it 's easily founded , and will by this means , being of one piece , be free of rifts , and leaks : thirdly , it being of Lead , will be of a considerable strength for resisting the force of the Water , that ordinarily breaks in pieces Vessels that are weak . I cannot well d●vine and guess the reason , why first it is round , and next narrower above , than below , unless , because its more easily founded after this way , than after another . This device here described is named a Diving Ark ; first , because it is of Timber , and next , because it saves a man from being overwhelmed with the Waters . I prescribe it of Wood , because of less trouble , and expence in making of it . 'T is four square , because it contains under this Figure , far more Air , than if it were round ; even as much more , as a square Vessel 30 inches wide , contains more than a round Vessel 30 inches wide . Now , the more Air , that 's in the Vessel , the easier is the respiration , and the longer time is the man able to abide under the Water , which two things are of great advantage to this Art . For if by a guess we reckon , how much more Air is in the one , than in the other , we will find in the Ark , as before it is described , 30 square foot of Air , but in the Bell , though it be 36 inches wide , as well above , as below , yet little more than 23 will be found , which is a considerable difference . But far less must be in it , seing it's narrower above , than below . Besides this advantage , there are others very useful : for being of Wood , it 's more tractable . Next , several Knags of Iron may be fastened conveniently to the sides within , to which a man fastning his hands , may keep his body fixed and sure in going down , and coming up . Moreover , if a man were in hazard to be confounded with fear , or lose the right exercise of his senses , and so be in danger of falling out of the Ark ; or if his feet should slide off the foot-stool , and his hands fail him too , a chord knit to one of those , and fastened about his wast or middle , might bring him up , though he were dead . Then , it s far easier to cut out a window or two in the sides of it , not very large , but little , as K and I , whereby , they being covered with Glass , a man may see at a distance , what 's upon the right hand , and what 's upon the left , and what is before . This device is of excellent use , for through the want of it , the Diver sees no more , but what is just below him , which sometimes , when he is near the ground , will not exceed the compass of a large Miln-wheel . But if so be , three holes be cut thorow , one on every hand , and one before , he may see as much bounds , and all things in it , as if he were not inclosed , and invironed with a cover . A little schelf likewise may be fixed upon the one side or the other , for holding a Compass with a Magnetical Needle , for knowing how such and such a thing lies in the ground of the Sea . In one of the corners may hing a little bottle with some excellent spirits , for refreshing the stomach , under Water . Many moe advantages I might name , this Engine being of Timber , but shall forbear ; leaving the collection of them to the ingenious Reader , and proceeds to answer some objections , that may be made against it .

First , if this Engine be made of Wood , it will not sink so easily , as being made of Lead . I answer , this difficulty is soon overcome , namely by making the Foot-stool the heavier : therefore how light soever it be , a weight may be found to counterpoise it in the Water , If it be judged too light in Timber , it may be lined with Lead , especially without . Secondly , if it be of Wood , there must be couplings and joynings in it , and so rifts and leaks in it , through which the Water may come . I answer , there is less difficulty here , than in the former ; because the joynts may be made so closs in all the parts , and may be so covered over with pitch , or with some such like matter , that it may defie either Water to come in , or Air to go out . Thirdly , if it be made of Wood , it will be in hazard of breaking by the force of the Water : for oft times its found , that the strongest Hogshead will burst asunder by the Pressure of it , if they go but down 7 or 8 fathom . I answer , this objection flows from the ignorance of the nature of Fluid bodies . If so be then , that a man knew , that the Pressure of Water is uniform , most equal , and presseth upon all the parts of a body within it alike , no such scruple would occurre . I say then , the Ark , though no thicker in the sides , than a thin sawen dale , will go down , in spight of all the Pressure that 's in the Water , not only 10 , but 20 , or 30 fathom , without all hazard . And the reason is , because what Pressure soever is without , to press in the sides , the same degree of Pressure is within to press them out . By this means , there is not one part of the Water , how deep soever , to which the Ark may come down , but there will be found as much force in the Air within , as will counterballance the whole weight without , as will be infallibly demonstrated afterwards . This answers a fourth objection , namely if holes be cut out in the sides of the Ark , in stead of windows , the force of the Water will break the Glasses in pieces , that covers them . There is here no hazard , though the said windows were 12 inches in Diameter : but it s not needful they be so large . It 's sufficient , if they be 2 inches wide : for a mans eye near to a hole , 2 inches wide , will see a great way about him . There 's a necessity the Glasses be joyned in with cement , that Water may not have access to come in , or Air to go out . In such a case ther 's no hazard , that the Pressure of the Water , will break through the windows , or break the Glasses ; because the Pressure of the Air within , being of the same force with the strength of the Water without , the Glasses are keeped intire . It may be enquired , what hazard would follow , upon supposition a small hole were pierced in the head of the Ark above , when it is going down ? I answer , ther 's not so much hazard , as a man would think ; provided the hole be not wide , but narrow . If it be wide , not only the Water comes in , but the Air goes out , the one thrusting it self by the other . If the hole be no wider , than the point of a bodkin is in thickness ; ther 's no danger at all : for by reason of the strait passage ; the one cannot thrust it self by the other , and therefore neither the Water can come in , nor the Air go out . And this comes to pass , by reason , that the Air within , is as strong as the Water is without . Now , if they be both of the same strength and force , why ought the Air rather to go out , then the Water to come in ; or the Water rather to come in , then the Air to go out ? I am confident , though the hole were as wide , as a man might thrust in his little finger , yet no irruption of Water , or eruption of Air would follow . This demonstrats clearly , that though a small rift , or leak should happen in the Ark , yet no hazard or danger would follow thereupon . If it be inquired , whither the greatest hazard is from the ingress of the Water , or from the egress of the Air ? I answer , ther 's no danger from the coming in of the Water from above ; because as it comes in , it falls down , and so mingles with the rest below . But if the Air should go out , the Ark fills presently full of Water , and drowns the man that is in it .

The next thing considerable in this Diving Instrument , is the foot-stool of Lead CD , that 's not only useful for a man to set his feet upon , when he dives ; but especially for sinking of the Ark. For this being made of Timber ; and full of Air , cannot of ' its own accord go down , unless it be pulled , and forced by some weight . It may either be broad and round , or square : if square , a large foot over from side to side , or 16 inches will determine the breadth . By this means , it will happen to be pretty thick , seing a great quantity of Lead is required . In each corner , there must be a hole , for four chords , by which it is appended to the mouth of the Ark. Between it , and the roof within , must be the height of a man and more . The weight of it , cannot be well determined without trial ; seing it depends upon the dimensions of the Ark. First then try , how much weight , will bring the top EFGH level with the surface of the Water . When this is found , add a little more weight till it begin to sink , and this will surely take it to the ground , though it were 40 fathom . 'T is to be observed , that when the top EF is level with the surface , there is here a just counterpoise , namely between the Lead foot-stool on the one part , as a pondus , and the Ark on the other part , as a potentia ; for with what force the Ark endeavours to pull up the Lead ; with the same force strives the Lead to pull down the Ark. Hence it is , that as a small weight will turn a pair of Scales , when they are in equilibrio ; so a small weight added to the foot-stool will sink the Ark. Though it may seem difficult to determine the just weight of the foot-stool , without trial as I said , yet I purpose to essay it . For this cause consider that there is no Vessel of Wood almost , if it be once full of Water , but the orifice of it will ly level with the surface of the Water , wherein it sweems . This proposition is so evident from experience , that it needs no confirmation . From this I gather , that as much weight of Lead or Stone will bring the top of the Ark EFGH , level with the surface of the Water , as is the weight of the Water , that fills it . If you suppose then the Ark to be 36 inches broad , and 40 inches high , it must contain 30 cubique foot of Water . Now , supposing each square foot of this Water to weigh 56 pound , 30 foot must weigh 1680 pound . This is gathered from trial and experience , for after exact search , I found a cubique foot of Water , in bulk about 16 pints of our measure , to weigh 56 pound . Take then a piece of Lead of that weight , and you will find it make a just counterpoise with the Ark. If any be desirous to know the quantity of it . I answer , if lead be 13 times naturally heavier then Water , you will find that a piece of Lead about 16 inches every way will do it . If it be objected , that when a mans body is within the Ark , the weight of the foot-stool must be less , even as much less , as is the weight of the man , whom I suppose to weigh 224 pound , or 14 stone . I answer , the whole weight of the man is not to be deduced from the foot-stool , but the one half only , and the reason is , because a mans body being of the same specifick and natural weight with Water , it cannot preponderat or weigh in Water , because magnitudes only naturally heavier then Water weigh in Water , as Lead , or Stone ; therefore seing the one half of the man is within the Ark , and the other without among the Water , that part only must weigh , that 's invironed with Air. This may seem a plausible answer , and might do much to satisfy these , that are not very inquisitive , yet , being examined , it will be found unsufficient . Therefore , I say , there 's not one part of the mans body , that weighs within the Ark , or makes it heavier . Yet , I affirm , that when the mans body is within the Ark , a less weight will sink it , then when his body is out of it , even as much less than before , as is the just weight of the one half of the man . For example , if 1680 pound be the just counterpoise of it without the Man , then after the Man is in it , it will take only 1568 pound to counterballance it , supposing the one half of the man to weigh 112 pound , or seven stone : yet it is not the weight of the man that makes this difference . For understanding what 's the cause of this alteration , consider , that when a mans body is within the Ark , there is less Air in it , then while his body is out of it , even as much less in quantity , as the bulk of the parts are , that are within . If this be , then must the Ark become heavier , not because the mans body makes it heavier , but because there is less Air , in the Ark , then before , and therefore , there arises an inequality between the weight of the foot-stool and the weight , or rather lightness of the Ark. For if 1680 pound of Lead , was the just counterballance of it , when it had 30 cubique foot of Air within it , it must exceed , when there is less Air in it . But there occures , here two difficulties , the first is , what 's the reason , why as much weight must be deduced from the foot-stool , as is the the precise weight of the one half of the man ? Secondly , how shall we come to the true knowledge of that weight ; that is , to know distinctly how many pounds or ounces it is of ? For answer , let us suppose , that the one half of the man , is just as heavy , as so much Water equal in bulk to his own half . This may be granted without scruple , seing a mans body is judged to be of the same specifick , and natural weight with Water : and though there should be some small difference , yet it will not make , or produce any insufficiency in the argument , for these demonstrations , are not Mathematical but Physical . Therefore , as much Water in bulk , as is equal to that part of the man , that is within the Ark , must be as heavy , as the half of the man . Now supposing the half of the man , to weigh 112 pound , and consequently that Water , to weigh as much , I affirm the said Water to contain 3456 cubique inches : but 3456 cubique inches , makes exactly two cubique feet , which I gather thus . Seven pound of Water requires 216 cubique inches , because a Cube of six inches , weighs exactly seven pound , therefore according to the rule of proportion , 112 pound will require 3456 inches , which amounts to two cubique foot . The Ark then by receiving the one half of the mans body , loseth two cubique foot of Air , therefore if 30 foot of Air , require 1680 pound weight of Lead to counterpoise it , 28 foot of Air , must require only 1568 pound : therefore to make a new counterballance , you must deduce 112 pound from the foot-stool . This answers both the difficulties . If it be said , that the foot-stool weighs less in Water than in Air , therefore it must be heavier , then 1680 pound . I answer , 't is needful to abstract from that difference , till the just calculation be once made , and that being now done , I say , that a Cube of Lead 16 inches weighing 1680 pound , ( If Lead be 13 times heavier than Water , ) will lose about 130 pound . The reason is evident , because a heavy body weighs as much less in Water than in Air , as is the weight of the Water it expells . But so it is , that a Cube of Lead of 16 inches expells a Cube of Water 16 inches : But a Cube of Water 16 inches weighs 130 pound , which I gather thus . 216 inches , or a Cube of six inches , weighs seven pound , therefore 4032 inches , must weigh 130 pound . For if 216 give 7 , 4032 must give 130. But to return . Though there be small difficulty to let it down and to sink it 20 or 30 fathom , yet there is no small difficulty to pull it up again . And the reason is this , because the further down it goes , the Air within , is the more contracted , and thrust up , by the Pressure of the Water , towards the roof . By this means , though near the top of the Water , there was little difference between the weight of the Lead and the Ark ; yet 9 or 10 fathom down , the difference is great , the weight of the one , far exceeding the weight of the other , and therefore there must be greater difficulty to pull it up from 10 fathom , than from 5 : and yet more difficulty from 20 than from 10. However , yet 't is observable that , as the Ark in going down , becomes heavier and heavier , so in coming up , it growes lighter and lighter : therefore less strength is required , in pulling it up from the tenth to the fifth fathom , than from the fifteenth , to the tenth : the reason is , because in coming up , the Air within expands it self , and fills more space in the Ark , which in effect makes it lighter , and more able to overcome the weight of the Lead . To make these things more evident , let us suppose , that when the Ark is down 18 or 20 fathom , the Air to be contracted by the force of the Water , from LM to PQ 12 inches . Next , that the weight of the foot-stool is 1680 pound . Now , if this weight was the just counterpoise of the Ark , at the top of the Water , then surely it must far exceed it now , when it 's 20 fathom down , because the Air that was 30 foot , is now reduced to 21. Count then , and you will find , that if 30 require 1680 , 21 will only require 1176 : therefore the weight of the Lead , will exceed the weight of the Ark , at 20 fathom deep , by 504 pound . This will be yet more evident , if we consider , that while the top of the Ark EFGH , is level with the surface above , the Water thrust out of ' its own place by this bulk , is just the weight of both Lead and Ark. But when ' its down 20 fathom , and the Air reduced from LM to PQ , there cannot be so much Water expelled now as before , seing the space LMPQ is full of Water . Now , I say , the Lead at 20 fathom , must be exactly so much heavier than the Ark , as is the weight of the said Water LMPQ , which in effect will be 504. pound : for ' its a square body , 36 inches in thickness and 12 in deepness . The weight of the rope is likewise to be considered , that lets down the Ark : for the longer it be , and more of it goes out , it 's the heavier , and more troublesome to pull up .

There is no way to cure this difficulty , but by finding out a way , how to keep a just counterpoise between the Lead and the Ark , all the time it is in going down . If the Air within did not contract it self , no difference would happen : but this is impossible , so long as the Water is under a Pressure . The expedient then must be found out another way , namely by kniting a small rope to the iron ring N , in length with the other , to which at certain distances , relating to the fathoms the Ark goes down , must be fastned empty little Vessels of Wood , or bladders , which by their lightness , may compense the decrement and decreasing of the Air. First then , let down the Ark three fathom , and see how much it is heavier than before : and as you find the difference , so fasten to R one Bladder , or two , till the Ark be brought near to a counterpoise . Secondly , let it go down other three fathom , and observe that difference also , and accordingly fasten to T as many , as will reduce the two to a counterpoise again . Do after this manner , till it sink 15 or 20 fathom . 'T is to be observed , that the further down the Ark goes , the difference is the less : therefore less addition will serve : and the reason is , because there is less Air contracted , in passing between the fifth and the tenth fathom ; than in passing from the first to the fifth . The proportion of contraction is represented by the unequal divisions within the mouth of the Ark , as 1.2.3.4 . In a word , by what proportion the decrement of the Air is , by that same proportion must the addition be , upon the rope SN . Suppose then , the Air to be diminished four inches , in going down four fathom , which will be 5184 square inches , or three square foot , then surely as much Air must be added to the rope SN , by bladders . In going down as far , let us suppose three inches to be contracted ; then less will suffice . Though it cannot be determined without trial , how much Air is contracted in three fathom , and how much in six , and how much in nine ; yet this is sure , that the decreasing is according to unequal divisions , that 's to say , less in six than in four , less in 8 , than in six , and less in 10 , than in 8 , and so downward : and that this is the rule , namely according to what quantity , the Air within the Ark is contracted , according to that same measure , must the addition of Air be to the rope . If it be said , that Bladders full of wind , cannot go down thorow the Water without bursting . I answer , 't is a mistake , because their sides being pliable , and not stiff like the sides of a Timber Vessel , they yeeld , and therfore cannot burst . It 's observable that when a bladder goes far down , the sides becomes flaccid and slagging . In this case , the Air , that before , had the forme of the Bladder , and was somewhat ovall , must now become perfectly globular , and round : for 't is sure , that the dimensions of it are altered by the Pressure of the Water , namely from more quantity to less : if this be , then the form must be round , seing the Pressure of the Water is most uniform ; even as drops of Water , or Rain from a house side are round upon this account . This second way , may be thought upon also . Make the Leaden foot-stool that sinks the Ark , not of one piece , but of many , that so , when the Air within it , begins to be contracted by degrees , in going down , a proportionable weight may be subtracted , for keeping a just counterpoise , all the while of the descent . Or because the greatest trouble is in bringing of it up , let the Diver , when once he is at the bottom , subtract so much weight from the foot-stool , as he thinks will go near to make a counterpoise , at that deepness . For example , if the weight of the foot-stool be 40 pound heavier than the Ark , then let him subtract 30 or 36 , which may ly , and rest upon the ground , till it be drawen up , at a convenient time , by a chord . By his means it will be easie to move the Ark , from one place to another . Next , there shall be little or no difficulty to pull it up . Nay , upon supposition , the rope were broken , by which it was let down , yet if the Diver please , he may come up without any mans help . And this is most easily done , namely by subtracting as much weight , as will make the Ark the stronger party . 'T is to be observed , that when you are at the bottom , and if you make the Lead but one pound lighter than the Ark , it will surely come up , and cannot stop by the way . The reason is , because a very small weight will turn the Scales , between two bodies , thus weighing in Water . Next , the further the Ark comes up , it becomes the lighter , because the Air within it , expands it self the more . But leaving this , let us come to explicat the reason , why the contraction of the Air is not uniform , but rather difform . For if in going down three fathom , three inches be contracted , there will not be other three contracted in going down the second three , but less : and yet less in going down the third three . Two things then are to be explicated here . First , why there is a contraction . Next , why it is after such a manner . As for the first ; the contraction is caused by the Pressure of the Water , which gradually increaseth from the top to the bottom ; as is clear from the last Experiment : therefore , there being a greater Pressure in a surface six fathom deep , than in a surface three fathom deep , the Air within the Ark , must be more contracted in passing between the third and sixth , than in passing between the first and third . When I say more contracted , the meaning is , that more quantity is contracted to less , whereby the Bensil of it is more intended ; or that the Air is more bended . As for the second , we must remember from the last Experiment , that the cause of this , is not from the Water , as if forsooth the Pressure of it , were according to unequal proportion , but from the Air it self , whose kind and nature it is , to suffer compression after such a way . 'T is evident in Wind-guns , whose second span of Air is comprest with greater difficulty , than the first : and the third with greater difficulty , than the second . 'T is so with all bodies endowed with Bensil : for ay the longer you bend , you find the greater difficulty . As there is a great disadvantage to the man that Dives , from the contraction of the Air , so there is a great advantage to him , from this manner and way of contraction ; for if it were uniform , according to the Pressure of the Water , then if three fathom comprest three inches , six fathom ought to compresse six inches , nine fathom nine inches , and so forward , till by going down , either the whole Air , should be comprest to no inches , or else very little should remain for respiration .

The next thing to be taken notice of , is that all the while , during the down going of the Ark , there is still equality of weight , between the Pondus of the Water , and the Potentia of the Air , for with what degree of weight , the Water presseth up the Air , with the same degree of force and power , doeth the Air press down the Water . If this were not , it would be impossible for a man to go down ; because of pain . For when one part of a mans body , is less prest than another , there ariseth a considerable pain , which sometimes is intolerable , as is evident from the application of Ventoso-glasses . This equality of weight , is the true reason , why respiration is so easie . Yet 't is to be observed , that a man cannot breath so easily in the Ark , under the Water , as above in the Air ; not because there is any inequality , between the weight of the Water , and the force of the Air ; but only because the quantity of it is little . For when a man sucks in as much Air , as fills his lungs , the quantity must be diminished : if this be , the Water must ascend by proportion , though insensibly . When a man thrusts out the same Air again , the quantity is increased ; if this be , then the Water must subside a little ; both which cannot be , without difficulty , seing there is a sort of ebbing and flowing both of the Air and of the Water , in every respiration . But it rather seems ( you say ) that this difficulty flowes from the strong , extraordinary bensil , that the Air is under . I answer , as long as the pressure of a Fluid is uniform , though in a high degree , yet there can be no trouble in respiration ; because with what force soever , it is driven in upon the lungs , with the same force it is driven out again : therefore , though the Air we live in , were as much again bended as it is , yet ( as is probable ) we would find no more difficulty in breathing than now . There is one thing makes breathing easie under the Water , in the Ark , namely this ; when a man sucks in the Air to his lungs , his breast and belly goes out , and so fills the space deserted by the Air , that goes in . This makes the ebbing and flowing far less .

From this equality of weight between the pressure of the Water , and the pressure of the Air , we see good ground to say , that though the Ark , were no thicker in the sides , than a thin sawed dale , yet there would be no hazard of breaking . I am confident , though it were no stronger in the sides , than a wine-glass , that 's soon broken ; yet it might go down 40 fathom without hazard , or danger of bursting . This affords good ground likewise to make windows in the Ark covered with glass : for if the Pressure be uniform , and equal , its impossible they can be broken . The Water cannot thrust them inward , because the Pressure of the Air , is as able to thrust them outward .

It 's certain , the more Air be in the Ark , the more easie is respiration : therefore it s more easie to breath , when the Ark is but down 5 fathom , than when it is down 10 or 15. It 's probable a man might live within the Ark , it being 40 inches deep , and 36 inches wide , at the deepness of ten fathom , near two houres ; whereas if it were round , and narrow above in form of a Bell , he could not continue an hour . It were very easie to try how long other creatures might live in it , for example dogs , and such like , or fowls , as hens , pheasants or doves . They might easily be inclosed from coming out ; for though the whole mouth of the Ark were shut up , except as much passage , as would receive a mans fist , yet it will operate , as well that way , as the other . And there , a little door might be made to open , and shut at pleasure . 'T is observed , that by long tarrying under the Water in the Bell , the Air becomes gross and misty , which hinders a man from seing about him . The cause of this , are vapors that come from the stomach , lungs and other parts of the body , especially from the stomach , when the ventricle is full of meat . It 's not fit then , that a man about to dive , should eat too much , or drink too much , especially such liquors as Sack or Brandy , that beget many fumes and vapors . If a man were necessitated to tarry a pretty while below , fresh Air might be sent down from above , in bottles or bladders , even as much as might fill up the place deserted by the contracted Air. 'T is observed by some , that have been under the Water , that their eares have been so troubled , that for a long time , they have found difficulty to hear distinctly . The reason of this must be from the great Pressure , the tympanum hath suffered from the imprisoned Air of the Bell. The Organ of hearing is soon troubled , especially when a man is near to a great gun , when it 's fired . And surely , when a man is but 34 foot down , the Air within the Ark , will be of double Bensil : put the case the man go down 68 foot , or 13 or 14 fathom , the Bensil is tripled : that 's to say , if the Air above have five degrees of Pressure in it , the Air of the Bell , at 68 foot deep , will have 15 degrees of Pressure ; therefore the tympanum of the ear that 's but a small and thin membran , must be sore distressed ; that is overbended , and prest inward ; even as , while a man sets upon a drum head a great weight , v. g. a Bullet of Lead or Iron , of 20 or 30 pound , the skin by this , suffers an extraordinary Pressure , whereby it is in hazard to be rent . 'T is probable , if a man should go very far down , the tympanum might be in hazard of breaking , or being rent in two pieces , there being a greater Pressure upon the one side from the Air without , than upon the other side , from the internal Air within , which is thought to be within the tympanum .

There remains another Phenomenon to be explicated , and it 's this : the further up the Ark comes from the ground of the Water , towards the top , the Water within it , subsides and settles down more and more , towards the mouth . The reason of it is , because the further up , the Pressure of the Water is the less ; and therefore the contracted Air gets liberty to expand , and dilate it self , and so thrusts down the Water from PQ to LM . In a word , by what proportion the Air is contracted in going down , by that same proportion it dilates , and opens it self in coming up . This lets us see , as there is disadvantage in going down , from the contraction of the Air , so there is advantage in coming up , from the dilatation of it . Some think , that the coldness of the Water is the cause , why the Air is contracted in the Ark , such are those , who deny the Pressure of it . But this fancy is easily refuted ; because in asserting this , they must maintain , the further down , the cold is the greater . If this be , then far more Air must be contracted , in going down from 10 to 15 fathom , than in passing from 5 to 10 ; seing as they say , the further down , the cold is the greater ; and therefore the contraction of the Air must be the greater ; that 's to say , there must be more quantity of Air contracted in the one space , than in the other . But so it is , that the further down , the contraction is the less . They judge likewise the coldness of the Water to be the cause , why the sides of empty Vessels are broken in going down . But if this be , then a strong Vessel should go no further down than a weak Vessel ; seing cold can pierce thorow the sides of the one , as well as thorow the sides of the other . And why is it , that a bladder full of wind will go down 40 or 50 fathom without bursting , yea 100 , and yet a stone-bottle or glass-bottle , cannot go beyond 20 or 30 ? If cold have in it , that power to break the sides of a strong bottle , it must be far more able to burst the sides of a thin Bladder . This difference is clearly explicated from the Pressure of the Water ; but I defy any man to shew the difference from the coldness of it . 'T is to be observed , that in all such Experiments of sinking of Vessels , as Hogs-heads , Barrels , and Bottles , they must be closs on all sides . Therefore , if a man desire to know , how far down a Glass-bottle is able to go without bursting , he must stop the mouth of it exactly , with a piece of wood , and cement .

In setting down the dimensions of the Ark , I have restricted them to 40 inches high , and 36 inches wide . But if any man be desirous to enlarge them , or make them less , he may do it . Only 't is to be observed , that the larger the Ark be , the Foot-stool that sinks it , must be the heavier . Yet it hath this advantage , that it contains much Air , which is the great perfection of it . One of a lesser size hath this advantage , that it 's more tractable , and easier to let down , and to be pull'd up . But these things are best known from Experience , or if a man please , he may calculate .

As the Ark is a most useful device for profit , so 't is excellent for pleasure , and recreation , if a man were disposed to see the ground and channels of deep Waters , or were inclined to find out Hydrostatical conclusions , a knowledge very profitable , and which few have attained to . Though it seem somewhat difficult to enter the Ark , and go down below the Water , yet a little use will expell all fear . Then , a man may go down with less hazard , and fear in the Ark , then in the Bell , because he may conveniently fasten his hands , to each side of the Ark , if need were . He may conveniently sit , as in a Chair , all the time of down going , and up-coming , by fixing a little seat in it : he may have windows to look out at : his body may be so fixed , that there needs be no fear of falling out .

If a man were desirous to make Hydrostatical conclusions , by Diving under the Water , the dimensions of the Ark might be enlarged , so that it might conveniently cover a mans whole body , by which means , having much Air in it , a Diver might continue under Water half a day , if need were . Let us suppose then , the hight of it to be 8 foot , and the breadth 3 foot , or more . In such a case , a man might continue under the Water many hours ; and yet not one part of his body wet : for if the Ark be 8 foot high , and the man 5 foot in stature , at the deepness of 10 fathom , the Water can scarce rise 3 foot in it . But why may not a man come up every half hour , when he finds difficulty to tarry down in a little Ark ? I answer , he may ; but it 's trouble and pains to pull him up , and let him down so frequently . And it may so happen , that through want of Air in a small Ark , he be necessitated to come up before he end his work . And leaving the work imperfect , he may find difficulty in the second down going , to find sometimes the place where he was , or the thing he was about to lift , v. g. a chest of Gold . If it be said , that a great weight of Stone or Lead is required to sink an Ark 8 foot high , which will amount to 4032 pound weight . I answer , 't is so indeed : but here is the advantage ; when it is once below the Surface , there 's little more trouble , then with an Ark of lesser dimensions ; because of the equipondium that's between it , and the weight , that sinks it .

In such a Vessel many trials might be made . As first , that of the Torricellian-Experiment , which is nothing else , but a Glass-Tub so many inches long , with a Mercurial Cylinder in it of 29 inches high , that 's supposed to be kept up at that hight by the Pressure of the Air. If this were taken down about 34 foot , 't is very probable the Mercury would rise other 29 inches . The reason is , because the Air within the Ark , that presseth upon the Surface of the stagnant Mercury , must be under as much pressure again , as the Air above ; but the Air above , is able to support 29 ; therefore this Air must sustain 58. The reason why the Bensil is exactly doubled is this , 34 foot of Water hath exactly as much Pressure in it , as the whole element of Air ; therefore , the Air within the Ark , being 34 foot down , must not only have in it the Pressure of the Air above , but the Pressure of the Water likewise : this necessarily follows , because when two Fluids touch , or are contiguous to other , the one cannot be under five degrees of Pressure , unless the other be under as many . According to this reasoning , if the Ark go down 68 foot , the Mercury will rise from 58 to 87. If to 102 , it rises 116. This reckoning is founded upon this , namely that Water is 14 times lighter than Mercury ; and therefore one inch of Mercury requires 14 of Water to support it in a Tub , and therefore , before Water is able to raise 29 inches of it , the Pipe must be 34 foot deep .

For a second trial , blow a Bladder as full of wind as it can hold , and having knit the neck about with a Pack-threed , place it in the Ark , and you will find the sides , that hath been stifly bended become flaccid and feeble , as if the one half of the Wind had gone out , and this will come to pass , before the Ark can go down eight or nine fathom . The strong bensil of the Air within the Ark is the cause of this : for as the Ark goes down , the Air grows stronger , and so at length becomes of that power and force , that it easily overcomes the force and Bensil of the Air of the Bladder , and reducing it to less room , causes the sides become flagging . In this case , the said Air , that was oval , and had the form of the Bladder , must become round in form of a Globe , because of the uniform Pressure , that it suffers from the Air of the Ark. When once the Ark is down 14 or 15 fathom , take the same bladder , and blow it stiff with Wind , and knit the neck as afore . And you will find that in the up-coming , the sides of it will burst asunder with a noise . When the Bladder is thus full of Wind , 't is supposed , that there is a sort of counterpoise between it , and the Air of the Ark. But as the Ark ascends , the Air of it , becomes weaker and weaker , while in the mean time , the Air of the Bladder suffers no relaxation ; therefore , when the Ark comes near the surface , there arises a great disproportion between the one Air and the other , as to strength , and therefore the Air of the Bladder being the strongest , rents the sides in pieces , and comes out with a noise . Or , blow it but half full of wind , and you will find before , the Ark come near to the top , the said Bladder to be bended to the full .

For a third trial , take a Glass , such as they use in Caves , for preserving of Brandy , and stopping the mouth closely , take it down with you in the Ark ; and you will see , the sides of it break in pieces , before you go down four or five fathom . The strong Bensil of the ambient Air , is the cause of this . If you take it down with the orifice open , no hurt shall befal it . Or if you stop the orifice in the up-coming , you will find the same hurt come to it . But here is the difference , in the first bursting , the sides are prest inward , by the ambient Air ; in the second , the sides are prest outward , by the Air within the Glass .

For a fourth trial , take a round Glass-bottle , pretty strong in the sides , and when it is down with you in the Ark 14 or 15 fathom , stop the mouth of it exactly , and when it comes above , you will find a considerable quantity of Wind come out of it , when the orifice is opened . This evidently demonstrats , that the Air within the Ark , 12 , 13 , or 14 fathom down , is under a far stronger Bensil then the Air above .

For a fifth trial , let a man apply to his skin a cold Cupping-Glass , when he enters the Ark ; and he will find such a swelling arise within it , as when it is applied hot by a Chyrurgion . This tumor begins to rise , assoon as the Ark begins to go down . The reason is evident from unequal Pressure , the parts within the Glass being less prest , than the parts without .

For a sixth trial , take a common Weather-Glass , and Place it in the Ark , and in the going down , you will see the liquor cre●p up in it , by degrees , as the Ark goes down , as if some extraordinary cold , were the cause of it . And as the Ark comes up by degrees , the said liquor creeps down by degrees . The cause of this Phenomenon is not cold , as some might judge , but the strong Bensil of the Air within the Ark , that so presseth upon the surface of the stagnant Water , that it drives it up . If you take with you , a Weather-Glass , hermetically sealled , no such thing will follow ; because the outward Pressure is keeped off . 'T is not then cold , that 's the cause , but weight . By the way take notice , that all common Weather-Glases are fallacious and deceitful ; because the motion of the Water in them , is not only caused by heat , but by the weight of the Air , which sometimes is more , and sometimes less , as frequently I have observed , and as hath been observed by others . This difference is found , by the alteration of the altitude of the Mercurial cylinder , in the Baroscope , which is more and less , as the Pressure of the Air changeth . In fair weather , and before it comes , the Mercury creeps up . In foul and rainy weather , and a pretty while , before it fall out , it creeps down . Because in fair weather , the weight of the Air is more , than in rainy and dirty weather . December , 13. 1669. I found the altitude 29 inches , and nine ten parts of an inch : at this time the heavens were covered with dry and thick clouds , and no rain followed . March 26. 1670. I found the altitude no more , than 27 inches , and nine ten parts , at which time , there was a strong Wind with rain . Between these two termes of altitude , I have found the Mercury move near a twelve moneth . 'T is a most sure prognosticator , for if after rain , you find the Mercury creep up in the morning , you may be sure , all the day following will be fair , notwithstanding that the heavens threateneth otherwayes . If after fair weather , the Mercury subside , and fall down a little , you may be sure of rain within a short time , though no appearance be , in the present . It falls down likewise , when winds do blow . What the true cause is , why there is such an alteration in the Pressure of the Air , before foul weather , and fair , and in the time of it , it is not easie to determine .

But we proceed . Trial likewise might be made , by firing a great piece of Ordnance above , whether the report would be heard below the Water or not ? This would determine the question , whether Water be a fit medium for conveying sound as Air is . Item , whether or not , the Sea water be fresher at the bottom , than near the top , which is affirmed by some . Item , whether sounds be as distinct in such a small portion of Air , as they are above . This might be tried with a Bell of a Watch. If need were , a little chamber Bell might be hung within the Ark , and a small chord might pass up from it , through the cover , whereby the persons above , might by so many tingles , speak such and such words to the Diver . I have demonstrated before , that though there were a little narrow hole made in the cover above , yet neither Air would go out , nor Water come in . If a man were curious , he might have a window not only in the sides , but in the roof above , covered with a piece of pure thin Glass , thorow which he might look up , after he is down two or three fathom , and see whether there appeared any alteration in the dimensions of the body of Sun or not , or seemed nearer .

We now come to infer some Hydrostatical conclusions , as from former Experiments . We see then first , that in Water there is a pressure ; namely from the strong Bensil of the Air within the Ark , that groweth stronger , and stronger , as the Water groweth deeper , and deeper . We see next , that the pressure of the Water hath an increment : because the further down the Ark goeth , the Air is the more bended . Thirdly , two Fluids cannot be contiguous one to another , unless both of them be under the same degree of pressure : because the Air of the Ark , and the Water that creepeth up within the mouth of it , are perpetually under the same degree of power , and force , whatever the deepness be . Fourthly , that in Fluids the pressure is uniform ; because the Air of the Ark , and the Water without , press most equally , one against the other . Fifthly , the more that the Air is bended , it is the more difficult to bend it ; and consequently , that the diminution of the quantity , is according to unequal proportion . Sixthly , that when the Ark is down 34 foot , the Bensil of the Air is doubled : and tripled , when it s down 68 foot : because the pressure of 34 foot of Water , is as much as the whole pressure , that 's from the Atmosphere . If it be enquired , how much weight rests upon the palm of a mans hand , when the Ark is down about 68 foot ? I answer , the pressure of the Water upon a mans hand , at that deepness with the pressure of the Air above , will be equivalent to the weight of a pillar of Mercury 87 inches high , and three inches thick , which will exceed in real weight 200 pound . If so much rest upon the palm , how much must rest upon the rest of the parts of the body ? Let us suppose then , the quantity of the palm , to be found in a mans skin , 200 times , then must he suffer as much pressure , and actually support as much burden , as will amount to 40000 pound weight . Seventhly , our bodies may be under a huge pressure , and yet that burden not perceptible ; as is evident from the Diver , who findeth little or no weight , while he is under the Water . Or if there be any Pressure found , it 's not comparable to that , which really is . Eighthly , when a man is 14 or 15 fathom down , at every inspiration and expiration , his breast and belly must lift up the weight of 1800 pound : because , if the whole burden be 40000 , the weight that rests upon the breast , and belly , will be about 1800. Ninthly , that between every inspiration , and expiration , there happens a perfect counterpoise , namely by the Air , that goeth into the lungs , and the outward Air of the Ark : for if the Pressure of the one , were more , than the Pressure of the other , there could be no motion of the lungs . Tenthly , when a man draweth his breath , the Air cometh not in by suction , but by pulsion . For this cause , though the Wind-pipe were stopped , yet a man might live by having a hole in his side , going into the lungs . Lastly , that there is no such thing as suction properly ; and therefore the motion of all Fluid bodies , is caused by Pressure and weight . The motion of the blood then thorow the heart , is driven , and not sucted . Infants properly do not suck , but have the milk squeezed into their mouth . 'T is evident from the sucking-glass that some women use for milking their own breasts : for by help of this , the Air that guardeth the head of the Pap is removed , and so the Air , that presseth the parts about , and without , squeezes out the milk .

Fig. 25 Pag. 179

EXPERIMENT XIX . Figure 26.

THis Figure represents a deep Water , whose first and visible surface , is FG. The imaginary surface , is ELC , 34 foot below it . ADB is a Siphon , working below this Water with Mercury . AEL is a Vessel with stagnant Mercury , among which the orifice A is drowned , the other orifice B existing among the Water ▪ DM is the hight of the Siphon above the line of level , which I suppose is 58 inches . For making it work , stop the two orifices closely , and pour in as much Mercury at a hole made at D , as will fill both the legs . Then stopping the said hole , open the two orifices A and B , and you will find the liquor run as long out at B , as there is any almost in the vessel AEL . For evincing this , which is the only difficulty , consider , that if this Siphon , were filled with Water , and made to work only with Air , ( as is clear from daily experience ) the liquor would run out constantly at B. Because there is here an unequal Pressure ; the surface of Air NB , being more burdened , than the surface ELC , but where unequal Pressure is in Fluids ( according to the 12th Theorem ) motion must follow , I prove the surface NB to be more burdened , than the surface ELC , because the Water BD , is heavier than the Water LD , as is evident to the eye . The Air B therefore , sustaining far more weight , than the Air EL , must cede and yeeld . Next , there is here a pondus and a potentia , the pondus is the Water LD ; the potentia by which it is counterpoised , is the Water BD ; but these are unequal , BD being heavier , than LD ; therefore according to the 33 Theorem , these two Fluids cannot cease from motion . If it be said , that the surface NB is stronger , than the surface ELC , seing it is lower . I answer , the difference is so unsensible , that they may be judged but one . Now , I say , if this Siphon work in Air , with Water , it must likewise , work in Water with Mercury . Therefore , this Siphon being 34 foot below the first sur●ace FG , the liquor must run out constantly at B. Because , there is here , an unequal Pressure , the surface of Water NB , be●ng more burdened , than the surface ELC. Though there be more weight in NB , than in ELC , because it is lower , yet because the difference is not so much , as is between the weight of BD , and the weight of LD , it proves nothing . Note here , that so long as D , is within 58 inches of EL C , this Siphon will work . The reason is , because the Pressure of 34 foot of Water , with the Pressure of the Air , upon FG , are able to raise Mercury exactly 58 inches . But if D exceed that hight , no Art will make the liquor run out at B. Note secondly , that this Siphon will operate with Air and Water , though the top D were 34 foot above M ; and the reason is , because the Pressure of the Air , is able to raise a pillar of Water to that hight . Note thirdly , that if there were an orifice opened at C , upon the level line ELC , the two Waters would become of the same weight , the one not being able to move the other . If you bore a hole at R , the liquor ascends from R to D , and goeth down from D to A , and so the motion ends . But , if the leg AD were six times wider , than BD , the liquor would not run out at B. I shall answer this in the close .

From this Experiment we see first , that the motion of Fluid Bodies up thorow Pumps , and Siphons is not for shuning vacuity , but because they are prest up violently . We see next , that when the Pressure is uniform , there is no motion in Fluids ; but assoon , as one part is more prest , than another , motion begins : because , this Siphon will not operate , if the orifice be made in C ; but if so be , it be in D , then the motion begins ; because there is here an unequal Pressure , which was not in the other . We see thirdly , that Fluids have a determinate Sphere of activity , to which they are able to press , and no further : because this Water , is not able to press Mercury higher than 58 inches . So the Air cannot raise Water higher than 34 foot . If this Water were 68 foot deep , the Sphere of it's activity would be 116 inches . We see fourthly , that in Fluids there is a Pondus and a Potentia ; and that the inequality of weight between the two , is the only cause of motion . We see fifthly , that as long as this inequality of weight continues , as long continues the motion , because , as long as BD , is heavier than LD , the motion perseveres . We see sixthly , the possibility of a perpetual motion in Fluids ; because the liquor runs perpetually out at B. If it be said , the motion ends , when the stagnant Mercury AEL faileth . I answer , this stop is only accidental , and not essentially from the nature of Fluids . If it be enquired , whether or not , would the Mercury run out at B , upon supposition , the shank LD were twice as wide , as the shank BD ? I answer it would . If it be said that the one is far heavier than the other , namely LD than DB. I answer , weight in Fluids is not counted according to thickness , but according to altitude .

EXPERIMENT XX. Figure 27.

THis last is for demonstrating the precise and just weight of any Pillar of Air , Water , Mercury , or of any other Fluid body , if some of their dimensions , be but once knowen . AB then is a square Pipe 12 foot high , and six inches in wideness , full of Water , resting upon the surface of Air AC . And EG is a square Pipe 12 foot high , and 12 inches wide , full of Water , resting upon the surface of Air EF. None needs to doubt , but the two Waters , will be suspended after this manner , even though the orifices A and E were downward , especially if they be guarded with Water , but the demonstrations , will be the more evident , that wee suppose the two Pillars of Water to be suspended as they are . From this Experiment I say first , that the Pillar of Air CD is 168 pound weight , at least ; which I prove thus . The Water AB is 168 pound : therefore the Air CD , must be as much . I prove the Antecedent , because it 's a Pillar of Water 12 foot high , and six inches thick : but every half cubical foot of Water , that containes 216 inches , weighs seven pound : therefore seing the Pillar is 12 foot , it must contain 24 half feet ; but 24 times 7 is 168. The only difficulty is to prove the Connexion , which I do thus , from the seventh Theor. all the parts of a Fluid in the same Horizontal line , are equally prest , but so it is , that the part A , and the part C , are in the same horizontal surface ; therefore the part A , and the part C , are equally prest . But if the part A , and the part C , be equally prest , the Pillar of Air CD , must be as heavy , as the Pillar of Water AB . I say secondly , that the Pillar of Air FH , weighs 672 pound , I prove it thus . The Water EG weighs 672 pound ; therefore the Air FH , weighs as much . The Antecedent is clear , because EG , is a square Pillar of Water 12 foot high , and 12 inches thick ; but every cubical foot of Water weighs 56 pound : but 12 times 56 , is 672. I prove the connexion , as before . All the parts of an horizontal surface , are equally prest ; therefore the part F , must sustain as much burden , as the part E.

To proceed a little further , let us suppose the Pipe AB to be 34 foot high , and the Pipe EG to be as much . I assert then thirdly , the Pillar of Air CD to weigh 476 pound , which I prove as before . All the parts of the same surface , are burdened with the like weight , but the part A sustains 476 pound , therefore the part C must support as much . The Connexion is evident , and the Antecedent is so too , because the Water AB being 34 foot high , and six inches thick , must weigh 476 pound : for , if 216 inches , weigh seven pound , 14688 inches , must weigh 476 pound . I assert fourthly , the Pillar of Air FH to weigh 1904 pound , which I demonstrat by the former Medium . All the parts of a Fluid that ly in the same horizontal surface , are equally prest ; but so it is , that E and F , do so ly ; therefore F must be as much burdened as E ▪ the Water therefore EG , weighing 1904 pound , the Air FH , must weigh as much . For if 216 inches of Water weigh seven pound , 58752 inches ( for so many are in the Water EG ) must weigh 1904 pound .

Let us suppose secondly , the Tub AB to be only 29 inches high , and the Tub EG , of the same hight , and that six inches wide , and this 12 inches wide . I affirm then fifthly , the Air CD to weigh yet 476 pound , and the Air FH , to weigh 1904 pound . Because the Pillar of Mercury AB , weighs 476 pound , and the Pillar of Mercury EG , weighs 1904 pound : therefore , if AB be 476 , CD must be as much . And if EG be 1904 ; FH , must be of the same weight . I prove the Mercury AB to weigh about 476 pound , though it be but 29 inches high ; because it is 14 times heavier then Water . For the same cause , doth the Mercury EG weigh about 1904 pound . I say about , because 34 foot , containes 29 inches , more than 14 times .

Let it be supposed thirdly , the Pipe EG , ( being 34 foot high , ) to have the one half of it IG , full of Air , and the other half EK full of Water , I affirm then sixthly , the part E , and the part F , to be yet equally burdened . That 's to say , the Water EK , that 's now but 17 foot , makes as great a Pressure upon E , as when it was 34 foot . The reason of this , is surely the Pressure of the Air IG , that bears down the Water KE , with the weight of 952 pound , the half of 1904 pound . If it be said according to the Theorem 21 , that there is as much Pressure and weight in the least part of a Fluid , as in the whole ; therefore the Air IG , must be as heavy as EH . I answer IG , is not so heavy as FH , because the Water EK impending in the lower part of the Tub , hath occasioned the Air IG , to expand it self so many inches , by which means , it loseth so many degrees of it's Bensil . If you remove the Water EK , then will the Air IG , be as heavy , as FH ; because EK being Air , it reduceth IG to that same degree of Bensil with it self ; but when the Air E is burdened with the Water EK , it cannot make the Air IG , of that same weight with it self .

Let us suppose fourthly , that only eight foot and an half of Water , are in the Tub , namely between E and N. I say then seventhly , that the part E , is as much burdened with it , as when the Pipe was full ; because the 25 foot , and an half of Air NG , is exactly as heavy , as the 25. foot and an half of the Water that 's gone . I prove it thus . The Air E hath the weight of 1904 pound in it self , seing the weight of the surface , is alwayes equal to the weight of the Pillar , but being burdened with the Water EN , that weighs 476 pound , it cannot press up with more weight then with 1428 pound : and therefore the top of the Water N , must press upon the under part of the Air , that 's contiguous with it , with 1428. If this be , the Air NG , must press down with as much , seing according to the 20 Theorem , it is impossible , that one part of a Fluid , can be under Pressure , unless the next adjacent part , be under the same degree of Pressure . Therefore I conclude , that the 25 foot and an half of Air NG , is as heavy , as the 25 foot and an half of the Water that 's gone . This makes it evident also , that when the Pipe is half full of Water , as EK , the Air IG , hath the weight of 952 pound . Because E being in it self 1904 , but being burdened with EK 952 , it cannot make the top of the Water K , press upon I with more weight than 952 ; and therefore ( by the 20 Theorem , ) the Air GI , must weigh 952 likewise .

I affirm eighthly , that , when the Pipe is full of Water ▪ from E to G , if a man poise it in his hand , he doth not find the weight of the Water EG . And the reason is , because it 's sustained by the part of the surface E. But if the Air E sustain it , my hand cannot sustain it . I find then only the weight of the Tub , but not the weight of the Water within it . I say ninthly , that when I poise the said Tub , I find the whole weight of the Pillar of Air LM , which is exactly 1904 pound . I prove it thus . The pondus of a Fluid is then only found , when there is not a potentia to counterpoise it , or at least , when the potentia is inferior to the pondus : but there is here no potentia , counterpoising the pondus of the Air LM . Therefore , I must find the weight of it , when I lift up the Tub. The major proposition is clear from the tenth Theorem . It 's evident also , from common experience ; for while a ballance is hanging upon a nail , with six pound in the one scale , and nothing in the other , you will find the whole burden , if you press up that one scale with the palm of your hand . But if so be , there were six pound in the opposite scale , you will not find the first six ; and the reason is , because it is in equilibrio with other six . 'T is just so here , I must find the weight of the Air LM , while I poise the Tub , because it wants a weight to counterballance it . I prove the minor proposition thus . If any thing counterballance the Air LM , it must either be the Air below , namely the part E ; or the Water EG : but neither of the twain can do it . Not the Air E , because it hath as great a burden upon it , as it is able to support , namely the Water EG , that weighs 1904 pound . And for this cause , not the Water it self , seing all the force it can have to counterballance LM , is from the surface of Air E ; but this is in equilibrio with it already . I said that the Air LM , was exactly 1904 pound weight . This also is evident , because it is just of these same dimensions , with the Air FH . If it be said , the Air LM must be thicker ; seing it's equal to the Tub without ; but the Air FH , is only equal to the Tub within . I answer , it is so indeed ; but here is a solution to the difficulty . I do not find the whole weight of the Air LM , but only as much of it , as is equal to FH . Suppose the Tub to be 12 inches within , from side to side , and 16 without , from side to side . I say then , I find only the burden of so much Air , as answers to the cavity of the Tub , because the rest of these inches , are counterpoised , by as much below , namely by the Air , that environs the orifice E : for it 's supposed , that if the Tub be two inches thick above , it must be as thick in the lips . So that the whole Tub , is not unequally prest , but only so much of it within upon the top , as answers to the cavity . Tenthly , that when the Pipe is but half full of Water , namely from E to K , I find only 952 pound of the Air LM , though before I found 1904. The reason is , because the one half of it is now counterpoised by the Air IG , and therefore the weight of it becomes insensible . 'T is clear from the sixth assertion , that the Air IG , presseth down with 952 ; therefore it must press up with as much , seing according to the sixth Theorem , the Pressure of a Fluid is on every side . Eleventhly , that when there is only eight foot of Water and a half in the Tub , namely between E and N , I find only 476 pound of the Air LM . Because in this case , the Air NG counterpoiseth 1428 pound of it . For if the said Air , burden the Water NE , with 1428 pound , as is clear from the seventh assertion , it must likewise press up the Tub with as much , and so counterpoise as much of the Air LM . Twelfthly , that when there is nothing within the Pipe but Air , the whole weight of the Air LM becomes insensible to me . The reason is evident , because it is wholly counterpoised by the Air within the Pipe . I affirm thirteenthly , that the Water EG , is in equilibrio with the Water AB : that 's to say 1904 pound , is in equilibrio with 476 pound . I prove it evidently , by the first medium ; all the parts of an Horizontal surface , are equally prest ; therefore the part A , sustains no more burden , then the part E , therefore AB , is as heavy as EG , and consequently , the Air CD , must be as heavy , as the Air FH . Lest this proposition may seem to contradict what is already said , I must distinguish a twofold Ballance , according to the third Theorem , one Natural , another Artificial . In the Artificial Ballance , where magnitudes do weigh according to all their dimensions , viz. Longitude , Latitude , and Profundity , the Water AB , and the Water EG , are not in equilibrio together , seing the one is 1428 pound heavier than the other . But in the Ballance of Nature , such as these Pipes are , all the four makes an equipondium together ; because they do not weigh here , according to their thickness , but only according to their altitude . Therefore seing AB is as high as EG , and seing CD is as high as FH , they must all be of the same weight .

From the first assertion I infer , that one and the same Fluid , even in the Ballance of Nature , may sometimes be in equilibrio with a lesser weight , and sometimes with a greater , because the Air CD , that weighs really 476 pound , is in equilibrio with the Water AB , that weighs but 168. This is , when AB is supposed to be only 12 foot high . It 's likewise in equilibrio with it , when it s 34 foot high . But how can AB , that 's 12 foot high , press A , with as much weight , as when it s 34 foot high ? I answer by a similitude , when a Cylinder of Wood 12 foot high stands upon a Table , it may burden it as much , as if it were a Cylinder 34 foot high . For , supposing it to be thrust in , between it , and v. g. the ceiling of the room above , it must press down with more weight , then if it were not thrust in . So , this Cylinder of Water AB , that 's but 12 foot high , being prest between the surface A , and the top of the Tub within , must burden A , as much , as if it were 34 foot high ; for being of this hight , it only stands upon the surface , without pressing up the top of the Tub.

I infer from the second assertion , that each Pillar in a Fluid hath a determinate weight . This is evident from the determinate weight of AB , that weighs first 168 pound , being 12 foot high , and 467 pound , being 34 foot high , and so of the rest . I infer secondly , that the thicker , and grosser a Pillar of a Fluid be , it is the heavier , ( even in the Artificial Ballance ) and contrariwise , the more slender and thinner it be , it is the lighter . This is evident from the Water AB , six inches thick , that weighs 476 pound , and from the Water EG , 12 inches thick , that weighs 1904 pound . So doth the Pillar of Air CD , weigh less , then the Pillar FH . Here is ground for knowing the certain and determinate weight of a Pillar , in any sort of a Fluid whatsoever . As to Air , its clear and evident , that a four-square Pillar thereof , 12 inches every way , weighs 1904. That 's to say , if it were possible , to take the Pillar of Air FH , in its whole length , from the surface of the earth , to the top of the Atmosphere , and pour it into the Scale of a Ballance , it would be exactly the weight of 1904 pound . Here is a secret : though that same Pillar of Air , were no longer , than 6 or 10 foot , yet the Pressure of it , upon the body , it rests upon , is equivalent to 1904 pound . If this be , ( you say ) what is the weight of Air , that rests upon this Table , that 's 36 inches square ? I answer , it must be as heavy , as a Pillar of Water 34 foot high , and 36 inches thick , which will , by just reckoning , amount to 17136 pound , or to 1071 stone weight . It may be inquired next , what 's the weight of the Air , that burdens the pavement of this parlour , that 's 16 foot square ? I answer 487424 pound . Because it is exactly the weight of a bulk of Water 34 foot high , and 16 foot thick . 'T is to be remembred , that though the Pressure of it , be so much , yet being poured into the scale of a Ballance , it will not weigh so much : for not only as much as fills the room must be taken , but as much as passeth from the pavement to the top of the Atmosphere . According to this method 't is easie to determine the weight of any Pillar of Air whatsoever , provided a man but once know the thickness of it , both the wayes , e. g. there 's a planum 12 inches long , and six inches broad , upon which rests a Pillar of Air. The weight of it then is , just the burden of a magnitude of Water 34 foot in hight , 12 inches in length , and six inches in breadth .

Though the weight of any Pillar of Air may be known , by knowing only the dimensions of it , in breadth and length ; yet the weight of a Pillar of Water cannot be known , unless all the three common dimensions of it , be first known . The reason is this , the Pillars of Air , are all of the same hight , but the Pillars of Water in the Ocean , are of different hights : therefore , not only must they be known , secundum longitudinem , & latitudinem , in length and breadth , but secundum profunditatem , that is , according to deepness . 'T is easie to know then , what each particular Pillar weighs . First then , try how much weight is in a cubical foot of Water , and having found this to be v. g. 56 pound , you may determine , that a Pillar of Water 34 foot high , and 12 inches thick , weighs 1904 pound . A Pillar 34 foot high , and six inches thick weighs 476 pound . Note , that in a Cube of Water six inches thick , there are 216 inches , which weighs seven pound . In a Pillar 12 inches thick , and 20 fathom , or 100 foot high , you will find 5600 pound weight . In one , of the same thickness , but 200 fathom high , there are 56000 , fifty six thousand pound weight . In a Pillar three foot square , and 20 fathom deep , there are 50400 , fifty thousand , and four hundred pound weight . Make it 200 fathom high with that thickness , and it will weigh 504000 , five hundred and four thousand pound . But , if according to the Theorem 25 , you consider ▪ the weight of the Air above , it will weigh 521136 , five hundred , twenty and one thousand , one hundred thirty and six pound . A Pillar 12 foot square , and 300 fathom deep , weighs 12096000 , twelve million , ninety and six thousand pound , Lastly suppose there were a bulk of Water 500 fathom deep , and 500 fathom thick , such a magnitude would weigh 8750000000. eight thousand seven hundred , and fifty million of pounds . But if the Pressure of the Air , that rests upon a surface of Water 500 fathom in breadth and length , be taken in , that weighs 119000000 , a hundred and nineteen million of pounds , the total , that the bottom of the sea sustains , must be 8940000000 , eight thousand , nine hundred and fourty million of pounds ▪ or 558750000 five hundred fifty and eight million , seven hundred , and fifty thousand stone weight .

I infer from the fifth assertion , that the lightest of Fluids may be brought to an equilibrium with the heaviest . For though Mercury be 14000 times heavier than Air , yet the part of the surface A , is no more prest with the Mercury AB , then the part C is prest with the Air CD . Secondly , that 29 inches of Mercury , are of the same weight with 34 foot of Water . Thirdly , the heavier a Fluid be naturally , it hath the less altitude in the Natural Ballance ; and contrariwise , the lighter it be , it hath the more altitude . This is clear from the Mercury , that 's 29 inches , the Water that 's 34 foot , and the Air , that 's counted 6867 fathom .

I infer from the sixth assertion , that two Fluids of different gravities , may make an equilibrium with a third of the same kind . Because the 27 foot of Air IG , and the 17 foot of Water EK , are in equilibrio with the Air FH . I infer secondly , that 17 foot of Air , may be as heavy as 17 foot of Water , because the Air IG , is exactly as heavy , as the Water EK . I infer thirdly , that the Bensil of a Fluid , is a thing really distinct , from the Natural weight of it : because the Pressure of the Air IG , is 952 pound ; but the natural weight of it will not exceed , if it were weighed in a Ballance , two or three ounces . I infer fourthly , that Air cannot suffer dilatation , but it must lose of it's Pressure . Because the Air IG , that ought to weigh 1904 pound , weighs only 952. For understanding this , you must know , that when a Pipe is about half full of Air , and half full of Water , and inverted , so much of the Water falls out , and consequently so many inches doth the Air above it , expand it self . So to make this Pipe that 's 34 foot high , half full of Air and half full of Water , you must pour in about 19 foot of Water , and the 15 foot of Air that 's in it besides , will , when the Pipe is inverted , go up and expand it self to 17 foot , two foot of Water falling out .

I infer from the seventh assertion , that when there are two Fluids of different gravities , and weights counterpoising a third , by what proportion the one grows lighter , by that same proportion the other becomes heavier . For , when the Water EK , that weighs 952 pound , becomes EN , that weighs 476 , the Air above it , that weighed 952 , becomes now 1428 pound .

I infer from the eighth , that the pondus of a Fluid , cannot be counterpoised , by two distinct powers . Because the 34 foot of Water EG , cannot be both sustained , by the part of the surface of Air E , and my hand . I infer from the ninth , that the Pressure and weight of a Fluid , may be found , even in its own Element , by sense . Because in poising of the Tub , I find the weight of the Air LM . I infer secondly , that the weight of a Fluid is only found in its own Element , when there is not a potentia to counterpoise the pondus of it , because I find only the weight of the Air LM , because it wants a potentia to counterpoise it . I infer thirdly , that it is very possible even in the Artificial Ballance , to weigh a Fluid in its own Element , and to know the precise weight of it , to a grain . For this cause , take a small chord , and fasten therewith the top of the Pipe G , to the Scale of a Ballance , and the Lead or Stone that makes the counterpoise in the opposite Scale , is the just weight of the Air LM .

I infer from the tenth , that by how much the nearer , the potentia of a Fluid , comes to the pondus , by so much the less , is the pondus found , or is sensible . This is clear , because I find less of the weight of the Air LM , it being counterpoised with the Air IG , than before . This follows likewise from the eleventh assertion . I infer from the twelfth , that when the pondus of a Fluid , is counterpoised , by an equal potentia , it becomes altogether insensible . I infer from the last , that two Fluids differing in weight , according to the Libra or Artificial Ballance , may agree in weight , according to the Natural Ballance . I infer secondly , that Fluids in the Ballance of Nature , do not counterpoise one another according to their thickness , but only according to their altitude .

Fig. ●● Pag. 1●4

Fig. 24 Pag. 152

Fig. 26. Pag. 182

Fig. 27 Pag. 196

AN ACCOMPT OF Miscellany OBSERVATIONS , Lately made , by the Author of the foregoing EXPERIMENTS .

OBSERVATION I.

IN May 1669 , there was need of a new Sink , on the east side of Tranent , for winning of Coals . But while the Coal-hewers were in digging down , and had come the deepness of 13 or 14 fathom , they were stopped from working by Damps , or ill Air , that flowed out plentifully from the sides of the sink , wherein there were a great number of Cutters , or rifts , out of which that ill Air came . To try the nature and power of Damps , I took a dog , and fastned him in a bucket , with a small roap , that he might not leap over , and when he had gone down 7 or 8 fathom , he presently begins to howl , and cry pitifully , as if he had been beaten sore with a rod , and a little after , he begins to stagger , and his feet failing him , he falls down , as one overtaken with the Epilepsy , and in going down to the bottom , his eyes turning in his head , they appeared very shining and clear like two large bright Diamonds . Fearing , that the Damp should have killed him out of hand , he was instantly pulled up from the bottom , where he had not tarried 15 seconds of time . And when the bucket had come to the mouth of the sink , he was pulled out , and laid upon the ground , to get fresh Air. When he had lien a while as dead , he begins at last to gape , and gasp , and make some respirations , as if he had been rather expiring , than recovering . Next , he began to stir and move his feet , and after , to raise himself upon his knees , his head staggering and wavering from side to side . After a minut or two , he was able to stand upon his feet , but so weakly , that he was not in capacity to walk or run . Yet at last , being much refreshed , he escaped from us , and ran home , but slowly . In the afternoon , the same Experiment was repeated , with another dog , whose case was the same in all things . But after he was perfectly recovered , for a further trial , we let him down the second time , and suffered him to tarry in the bottom of the sink , about the space of three minuts : but when he was pulled up , and taken out , we found no symptomes of life in him ; and so after half an hour and more , his body began to swell , which ordinarily befalls such , who are killed after this manner . After this , we sent down in the Bucket , a little Chicken , which , when it came near the Damp , presently slapped with the wings , and falling down , turned over and over for a pretty while , as if it had been taken with a vertigo , or giddiness . But by drawing up the Bucket in haste , and bringing the Bird to the fresh Air , it recovered . In the evening , we let down a lighted Candle , but it was soon extinguished , when it came near mid-sink ; for here , rather than in the bottom , was the strongest Damp. Lastly , we let down by a chord , a Brand-iron , with burning Coals , whose flame was soon put out , and after a little while , we perceived the red Coals to be extinguished by degrees ; yet not totally , because , as the Coal-hewers observed , the power of the Damp was not so strong , as before . These Damps then have their ebbings and flowings , which seem to depend upon the weather , or rather upon the situation of the winds , and their force . For 't is observed , that a high South-west wind causeth ill Air in this place ; and that , by reason of much wast ground , that lies upon the South , and South-west hand of this Sink , whence are conveyed under ground by secret passages , which are nothing else but so many rifts and openings , commonly called by the Coal-hewers , Cutters , corrupted and rotten Air , full of sulphurious stems . The reason why these passages are open , and replenished with nothing , but corrupted Air , is this , the Water , that 's ordinarily called the Blood of the Coal , being withdrawn with subterraneous Gutters ( commonly called Levels ) that are digged , and wrought under ground , sometimes a very long way , for drying of the Mines , and the veins of the earth being now empty , there succeeds Air ; which Air , by process of time , and long standing , rots , and contracts a sulphurious quality , which causeth sudden death . Now , when the wind is high , and strong from the South or South-west , that sulphurious Air is driven through the ground ▪ and coming to Sinks and Mines , where men are working , presently infects the place , and hinders the work . 'T is often observed , that the wind and Air under ground , keep a correspondence in their motion , with the wind above ground : and therefore , when the wind is in such a point above , 't is found , that the motion of the Air below runs such a way , and the contrary way , when the wind above ground , is in the opposite point . When there is a free passage between the bottom of the two Sinks , you may observe the wind come down through the one , and running alongst under the ground , rise up thorow the other , even as Water runs thorow a Siphon . For this cause , when the Coal-hewers have done with such a Sink , they do not use to stop it , or close it up , but leaves it standing open , that the Air under ground may be kept under a perpetual motion and stirring , which to them is a great advantage . 'T is very strange to see sometimes , how much Air , and how fresh it will be , even at a very great distance , namely four or five hundred pace , from the mouth of the Sink . This could never be , unless there were a considerable Pressure and weight in it , whereby it is driven forward , thorow so many Labyrinths . And even in the utmost room , where the Coal-hewers are working , the Pressure is as great , as it is above ground , which is found by the Torricellian Experiment . In such a case , the Air cannot press down thorow the Earth and Metalls , therefore the Mercury must be suspended , not by a Pillar from the Atmosphere , but by the Bensil of it . Nay , put the case , that the whole Element of Air were destroyed , and this remaining , yet would it be able to support 29 inches . To shut up this discourse , it is observed by the Coal-hewers , that when there is ill Air in a Sink , a man may perceive distinctly , what is lying in the bottom , so clear and transparent is the Air of it : but when the Damp is gone , the Medium is not so clear . In temperat and cold weather , the Damps are not so frequent . From this Sink , in soft winds , or in Northerly winds , or when it blows from East or North-east , the Damps are driven away .

OBSERVATION II.

JUpiter upon Wednesday night , at eleven a clock , being 24 of November , 1669 , had the following position with the stars of Gemini . He was so near to the Star C , that to appearance , the points of his rayes did touch it . This Star by looking upon the material Glob , is fixed in the very Zodiack , and in the 13 degree of Cancer , and is the very navel of the following Twine . The Star A is Castor . The Star B is Pollux . The star D , is fixed in the forefoot of the following Twine . From this place he moved , with a retrograde motion , till he came to the 5 of Cancer , about the 20 of February , 1670 , and from that time became Direct in his motion , and so upon the 27 of March , 1670 at 9 a clock , he was in a right line with Canis minor , and the brightest Star in Auriga , and was in a right line with the eastmost shoulder of Orion , and Castor in Gemini , or with that Star , when South-west , that 's highest , and West-most .

OBSERVATION III.

IT is written in the History of the Royal Society , that such a member of it , whose name I have forgotten , hath found out , among many other curious inventions , this , namely a way for knowing the motion of the Sun in seconds of time : but is not pleased to reveal the manner how . Because such a device may be usefull in Astronomy , and likewise for adjusting the Pendulum Clock , I shall therefore briefly shew , the manner and way how such a thing may be done , as I have tried it my self . I took an Optick Tub , about 12 foot long , only with two Convex-glasses in it , and did so place it in a dark room , by putting the one end , in which was the Object-glass , without the window , and keeping the other within , that I caused the beams of the Sun shine thorow it , which were received upon a white wall four or five foot from the Tub. This image , which was perfectly round , and splendid , did move alongst the wall very quickly , so that in a minut of time , it did advance seven inches and a half , which will be the eight part of an inch in a second , a motion very sensible . Now , this beam that came thorow the Tub , and lighted upon the wall , would not have moved one inch in a minut , if it had wanted the two Glasses ; for as they magnify , and seem to bring nearer the Object , so they quicken the motion of it . In a word , by what proportion the Object is made more , by that same proportion is the motion quickned . 'T is to be observed , that the longer the Tub be , the motion is the swifter : for as the longest Tub doth ordinarily most magnify the object ; so doth it most quicken the motion . Next , the farther distant the white wall is from the end of the Tub , the larger is the image ; and contrariwise , the nearer it be , it is the less . Thirdly , the farther the wall be from the end of the Tub , the circumference of the image is the more confused , and the nearer it be , it is the more distinct . Fourthly , the darker the room be , it is so much the better . Lastly , this trial may be made with ordinary Prospects , of a foot , two foot , or three foot long , which will really do the thing , but not so sensibly , unless the glasses be very good .

As to the use of this device in Astronomy , I shall not say much . But shall only mention what it may serve for in order to the Pendulum Clock . For this cause , let a man choise a convenient room , with a window to the South , wherein this Tub may be so fixed , that it may ly just , or very near to the true meridian , and may move vertically upon an axil-tree , because of the Suns declination every day . Then at a certain distance from the end of it , fix and settle a large board of timber , smooth , and well plained , and well whited , for receiving the image . In the middle of this board , draw a circle with Charcoal , equal in diameter to the circle of the image . Now , this being done , you will find that assoon as the west side of the Sun , begins to come near to the Meridian , the image begins to appear upon the board , like the segment of a circle , and grows larger , and larger , till it become perfectly round . Now in the very instant of time , wherein the image , and the circle are united , set the wheels of your Clock a going , from the hour , minut , and second of XII . To morrow , or 3 or 4 dayes after , when you desire to make an examination , wait on about 12 a clock , when the Sun is coming to the Meridian , and you will find what the difference is . If the Clock go slow , observe , assoon as the image is united with the circle ( which you will perceive in a second of time ) the variation , that 's to say , how many seconds interveens between that second , wherein the union fell , and that second , that closes XII hours in the Clock . If it go fast , observe how many seconds passes from that second , that ends XII hours , and that wherein the image of the Sun is united with the circle , which if you do , you will know exactly , what the difference is , even to a second . But without this , you will find great difficulty to know the variation in 15 or 20 seconds , especially in a common Dial. But here , you will see distinctly the image of the Sun move every second of time , the eighth part , or the sixth part , or the fourth part of an inch , according to the length of your Tub , and goodness of your glasses . 'T is to be observed , that in adjusting the Pendulum Clock , respect must be had to the table of Equation of dayes , commonly known in Astronomy . For if this be not , it is impossible to make it go right , and that because all the natural dayes of the year , are not equal among themselves : that 's to say , the time that 's spent by the Suns motion from the Meridian this day , to the same Meridian , the next day , is not equal , but is more or less , than the time spent betwixt Meridian and Meridian , a third or fourth day after . For instance , the Sun this day being 11 of Iuly , comes sooner to the Meridian by three seconds of time , than he came yesterday . Within 9 or 10 dayes , ( suppose the 22 of Iuly ) he will be longer in coming to the Meridian by 4 seconds , than upon the 21. This difference I grant , in short time is not sensible , yet once in the year , it will amount to more than half an hour . This inequality of dayes arises from two-causes . First , from the Suns eccentricity , whereby he moves slowlier in one part of the Zodiack , than in another : for in Summer when he is furthest from the Earth , he goes slowlier back in the Ecliptick , than in Winter , when he is nearer to it . The second cause , which is truly the far greater , is this , because in the diurnal motion of the Sun , equal parts of the Aequator , does not answer to equal parts of the Zodiack . Hence it followes , that if the natural dayes be not equal among themselves , the hours must be unequal also : but this is not considerable .

By help of such a Tub placed in a dark room , it is easie , when the Sun is under Eclipse , to enumerat distinctly the digits eclipsed . Likewise , if you take out the object Glass , and cover a hole in the window board with it , you shall see distinctly upon a white wall , the species and true representations of all objects without . And by comparing the quantity of the object without , with the quantity of it within , you may know the distance of it from the window , though it were many miles . For as the one quantity , is to the other , so is the distance between the Glass and the object on the wall , to the distance between the Glass and the object without .

It may be inquired whether or not , the retrograde , as well as the diurnal motion of any of the Planets , may be discerned , in minuts or seconds , by the help of a long Telescope ? In answer to this , we must suppose the Planets only to have a retrograde motion , and consequently to move slowly from West to East , Saturn once in 29 years , or 30 , to run about the Zodiack ; Iupiter in 12 , Mars in 2 years , the Sun in one year , Venus and Mercury in less time , and lastly the Moon in a moneth . Now I say , it is impossible by the longest Tub , that the greatest Artist can make , to discern the motion of the inferior Planets , far less the motion of the superior , either in Minuts or in Seconds , and that by reason of the great tardity , and slowness of the motion . Notwithstanding of this , I am induced to think , that the retrograde motion of the Moon might be discerned , at least in Minuts . For evincing of this , let us suppose which is true , that the Sun runs from East to West half a degree in two Minuts of time , seing in an hour he runs 15 degrees . Next , that the Moon goes about the Zodiack in 27 dayes and 7 hours , namely from that same point , to that point again , and consequently runs back every day 13 degrees and about 10 Minuts . By this account , she must retrograde half a degree , and about 2 minuts of a degree every hour . The Sun then runs half a degree in two Minuts , and the Moon half a degree in 60 Minuts ; therefore the Moon must be 30 times slower in her retrograde motion , than the Sun is in his diurnal motion . Let us suppose next , as I observed with a Tub 12 foot long , that the image of the Sun runs the eighth part of an inch every second , and consequently , seven inches and an half , in a Minut : then must the image of the Moon with that same Telescope , run the thirtieth part of seven inches and a half in a Minut , seing she runs 30 times slowlier ; therefore in every Minut of time she must advance the fourth part of an inch , which will be very sensible . Though we grant , that the Moon hath no retrograde motion properly , yet by comparing the diurnal Motion of the Moon , that 's slower , to the diurnal motion of the Sun , that 's swifter , we shall really find the thing it self . Therefore in the time of a Solar Eclipse , this retrograde motion is conspicuous , which by an ordinary Telescope may be discerned in Minuts . Assoon then as the East side of the Moon , begins to enter upon the West side of the Sun ( the greater the Eclipse be , it is the better ) observe , and you will find the one image , which will be black , cover the other by degrees , that 's splendid , and run in every minut of time , the fourth part of an inch of the Suns diameter , provided alwayes , that the Sun run the eighth part of an inch in a second .

OBSERVATION IV :

UPon Tuesday the 19. of Iuly 1670 , the following Experiment was made . In the middle Marches between Scotland and England , there is a long tract of Hills , that run from Flowdon , many miles South and South-west , amongst the which , the Mountain Cheviot is famous beyond , and conspicuous above all the rest for altitude , from whose top a man may discern with one turning of his eye , the whole Sea-coast from New-castle to Berwick , much of Northumberland , and very many Leagues into the great German Ocean : the whole Mers and Teviotdale , from the foot of Tweed , to very near the head of it : Lauderdale , and Lammer-moor , and Pentland hills above Edinburgh . The North side of this Mountain is pretty steep , yet easie to climb , either with men or horse . The top is spacious , large and broad , and all covered with a Flow-moss , which runs very many miles South . When a man rides over it , it rises and falls . 'T is easie to thrust a Lance over the head in it . The sides of this Hill abounds with excellent Well-springs , which are the original of several Torrents , amongst the which Colledge-Water is famous , upon which , not a mile from the foot of this Mountain is White-hall . The adjacent Hills are for the most part green , and excellent for the pasturage of Cattel . Not many years ago , the whole Valleys near the foot of Cheviot , were Forrests abounding with Wild-Deer .

Upon the highest part of this Mountain was erected the Torricellian Experiment for weighing of the Air , where we found the altitude of the Mercurial Cylinder 27 inches and an half . The Air was dry and clear , and no wind . In our Valley-Countreys , near to the Sea-Coast , in such Weather , we find the altitude 29 inches and an half . When this difference was found , care was taken to seal up closly with Bee-wax , mixed with Turpentine , the orifice of the Vessel , that contained the stagnant Mercury , and thorow which the end of the Pipe went down . This being done with as great exactness as could be , it was carried to the foot of the Mountain in a Frame of Wood , made on purpose , and there opening the mouth of the Vessel , we found the Mercury to rise an inch and a quarter higher than it was . The reason of this strange Phenomenon must be this , namely a greater Pressure of the Air at the foot of the Hill , than upon the top : even as there is a greater Pressure of Water in a surface 40 fathom deep , than in a surface 20 fathom deep . 'T is not to be doubted ▪ but if the root of the Mountain had been as low as the Sea Coast , or as the surface of Tweed at Kelso , the Mercurial Cylinder would have been higher . This way of observing , seems to be better than the common : for while the Baroscope is carried up and down the Hill , without stopping the orifice of the Vessel , that contains the stagnant Mercury , the Cylinder makes such reciprocations , by the agitation of a mans body , that sometimes abundance of Air is seen to ascend up thorow the Pipe , which in effect makes the Cylinder shorter than it ought to be . But if so be , the end of the Pipe be immerged among Quick-silver , contained in a Glass with a narrow orifice , so that it may be stopped compleatly , you will find no reciprocations at all . And to make all things the more sure , the Glass may be filled up either with Mercury , or with Water above the Mercury ; by which means the Cylinder in the down-coming , or in the up-going shall remain immoveable . Besides the stopping of the orifice of the said Glass , you may have a wider Vessel , that may receive the same Glass into it , and it being full of Water , may so cover the sealed orifice , that there shall be no hazard of any Air coming in . Or this Experiment may be first tried at the root of the Hill , and having stopped compleatly the mouth of the Vessel , the whole Engine may be carried up to the top , where you will find the Mercury subside and fall down so much ; namely after the said orifice is opened : for as the stopping of the orifice at the root of the Hill , is the cause , why that same degree of Pressure remains in the stagnant Liquor ; so the opening of it upon the top of the Hill , is the cause why it becomes less .

This Experiment lets us see , that the Pressure of the Air seems to be as the Pressure of the Water , namely the further down the greater ; and the further up the less : and therefore , as by coming up to the top of the Water , there is no more Pressure , so by coming up to the top of the Air , there is no more weight in it ; which in effect sayes , that the Air hath a determinat hight , as the Water hath . From this Experiment we cannot learn the determinat hight of the Air , because the definit hight of the Mountain is not known . I know there are some , who think that the Air is indefinitly extended , as if forsooth , the Firmament of fixed Stars were the limits of it , but I suppose it is hard to make it out .

OBSERVATION V.

JUne 5. 1670. I observed the Sun within 3 minuts of setting , to have a perfect oval figure , the two ends lying level with the Horizon . His colour was not red as ordinarily , but bright and clear , as if he had been in the Meridian : neither was the Sky red , but clear also . And by the help of the Pendulum Clock , I have observed his body to be longer in setting than it ought , by eight minuts , and sometimes by ten , and his Diameter longer in going out of sight than it ought , by two , and sometimes by three minuts . The reason of these Phenomena , must be the Refraction unquestionably .

OBSERVATION VI.

UPon Saturday evening the 30 of Iuly 1670 , and the night following , till about two a Clock in the Sabbath morning , there fell out a considerable rain , with great thunder , and many lightnings . About Sun-set , the convocation of black clouds appeared first towards the Horizon in the South-west , with several lightnings ; and the wind blowing from that point , carried the clouds and rain over Mid and East-Lothian , towards the Firth and Sea-coast . About 9 a clock , the whole Heavens almost were covered with dark clouds , yet the rain was not very great , neither were the thunder claps frequent , but every fifth or sixth second of time , a large and great lightning brake out . But before the thunder crack was heard , which happened every fourth o● fifth minut , the lightning was so terrible for greatness , and brightness , that it might have bred astonishment . And because the night was very dark , and the lightning very splendid , a man might have perceived houses and corn-fields at a great distance . And if any had resolved to catch it , in the breaking out , it did so dazle the eyes , that for half a minut , he was not able to see any thing about him .

Sometimes the lightning that went before the thunder , brake forth from the clouds , like a long spout of fire , or rather like a long flame raised high , with a Smiths Bellow● , but did not continue long in sight . Such an one above the Fi●th was seen to spout downward upon the Sea . Sometimes there appeared from the one end of the cloud to the other , an hiatus , or wide opening , all full of fire , in form of a long furrow , or branch of a River , not straight , but crooked . I suppose the breadth of it , in it self , would have been twenty pace and more , and the length of it five or six hundred pace : the duration of it , would have been about a second of time . Sometimes a man might have perceived the nether side of the cloud , before the crack came , all speckled with streams of fire , here and there , like the side of an Hill , where Moor-burn is , which brake forth into a lightning . But there was one , after which followed a terrible thunder crack , which far exceeded all the rest , for quantity and splendor . It brake out from the cloud , being shot from North to South , in form of fire from a great Cannon , but in so great quantity , as if a Gun ten foot wide , with 500 pound weight of Powder in it , had been fired . And surely the lightning behoved to be far greater in it self , seeing it appeared so great , at so great a distance . It did not evanish in an instant , like the fire of a Gun , but continued about a second and an half ; by reason ( it seems ) that it could not break out all at once . This did so dazle the sight , that for half a minut almost , nothing was seen , but like a white mist flying before the eyes . The whole Countrey about was seen distinctly .

All these great lightnings were seen a considerable time , before the crack was heard . Sometimes 30 seconds numbered by the Pendulum Clock interveened , namely when the thunder was at a distance , about 7 or 8 miles . Sometimes 15 or 16 only interveened . But when the thunder was just above our head , no moe passed , than 7 or 8 , which seems to demonstrat , that these thick black clouds , out of which the thunder breaks , are not a Scottish mile from the earth , when they are directly above us .

'T is observable , that in all lightnings , and thunderings , there is no smoke to be seen , which seems to evince , that the matter whereof they are generated , must be most pure , and subtil . Who knows , but this Countrey , that abounds with Coal , may occasion more thunder and lightnings , than other places , namely by sending up sulphurious exhalations to the middle region of the Air , wherewith the Coal-mines abound .

OBSERVATION VII .

THis is a method for finding out the true South and North Points , which are in effect very difficult to know . Take therefore four pieces of Timber , each one of them five foot long , and about six inches thick , square-wise . Sharpen their ends , and fix them so in the ground , that they may stand Perpendicular , and as near to South and North , by a Magnetick Needle , as may be . The place would be free of Trees , or of any such impediment , that it may have a free prospect of the Heavens . As for their distance one from another , let the two North-most , and the South-most be two foot asunder : let the two East-most , and two West-most , be but one foot , making as they stand , an oblong quadrangle . For keeping them equidistant above , as well as below , take four bars of Wood , about three inches broad , and one inch thick , and nail them round about upon the four sides , on each side one , so that being nailed on Horizontally , they may make right angles , with the tops of the standards above . There are then for distinctions cause , the North-bar , and the South-bar , that runs East and West , and the East-bar , and the West-bar , that runs South and North , There is here no difficulty in the thing it self , but only in the fancy to conceive it . Besides these four , there must be other four of the same form and fashion , nailed on arder down about the middle of the four standards . Take next some small Brass Wyre strings , such as are used in Virginals , and fix one from the middle of the South-bar , that 's upmost , to the middle of the South-bar just under it . Fix it so , that it may be exactly Perpendicular , which may be done , with a great weight of Lead . Take a second Wyre string , and hang it plumb from the West end of the North-bar , and another from the East end of the same Bar , I mean the Bar that 's nearest to the top . These three strings so fixed , will go near to make an equilateral triangle .

Now because the device is for finding out the Meridian by the Stars in the night time , not by any indifferently , but by these that are nearest to the Pole , therefore observe in Iuly and August , when the Guard-stars in the evening begin to come down towards the West , and keeping closs one eye , bring the other somewhat near to the South-most string , and order your sight so , that this string , and the West-most string upon the North side , may catch the foremost Guard-star in the down-coming , when it is furthest West , and there fix it . When the same Star is turning up towards the East , catch it by the South-most string , and the East-most string on the North side , and your work is done , if so be , you divide exactly , between the East-most and West-most , and there hang a fourth string , which with the string upon the South-side , gives you the true South and North. For better understanding , note first , that , when the Guard-stars are coming down , or going up , the Altitude varies quickly , but the Azimuth , or motion from East to West , will not vary sometimes sensibly in two hours almost , which is a great advantage in this case . But when you find out the Meridian with a Plain , and a Perpendicular Stilus , by the shadow of the Sun , if it be not when he is about East and West , the Azimuth alters more than the Altitude , wh●ch is a great disadvantage . Now its certain , the slower the motion be from East to West of any Star , it is the easier to observe , and it is the more sure way . Note secondly , that special care must be had , to cause the strings hang Perpendicular . Note thirdly , that before you begin your Observations , the South-most string must be made immoveable , but the East-most , and West-most , on the other side , must not be so , because as the Stars in going about move from East to West , so must the said two strings be left at liberty , to move a little hither and thither , till the Observations be ended . Note fourthly , that assoon as you perceive sensibly , the foremost Guard-star to decline towards the West , then you must begin to observe , which is nothing else , but to fix your eye so , that the South-most and West-most string , may cover the said Star . And because in coming down , it goes West , therefore , let the West-most string move towards the left hand by degrees , following the Star to its utmost , till it be covered by them both . Follow the same method , in observing the same Star in going up towards the East . Note fifthly , that when you make the two strings cover the Star , that which is nearest to the eye , will appear transparent , and of a larger size , so that you may perceive distinctly thorow it , not only the Star it self , but the other string also , which is a great advantage . This is evident to any , who holds a bended silk threed between their eye and a Star in the night time ; for when you direct your sight to the Star , the string appears like the small string of a Virginal when it trembles . Note sixthly , that in observing in a dark night , you must have a Cut-throat , that by the light of the candle you may perceive the strings . Some other things might be noted , but you will find them better by experience , than they can be exprest here .

I named Iuly and August in the evening for observing the Guard-stars , when they are West-most , but there are several other seasons , when this may be done as conveniently . They are East-most in the latter end of October , and beginning of November about 5 or 6 a clock in the morning . If a man were desirous to make this observation quickly , I suppose he might in the end of October , find the said stars West-most in the evening , and East-most the next morning . Besides the Guard-stars , a man may make use of the Polar-star ; for as it goes higher , and lower than the true Pole , by 2 degrees and 26 minuts , so it goes as much to the East , and as much to the West , once in 24 hours . In the end of Iuly , you will find the Polar-star East-most , about 9 a clock at night , and in the end of Ianuary West-most at 9 a clock . Note , that every month , the fixed stars come sooner to the same place by two hours : therefore in the end of August the Polar-star must be West , at 7 a clock at night , and East at 7 a clock in the morning . When the Meridian is found out after this manner , there is no Star or Planet can pass it , but you may know exactly when , be it never so high , or never so low . For there is nothing to be done , but to wait , till the South-most and North-most string cover the body of the Star . If it be the Sun , hold up a white Paper , behind the two strings , and when their shadows do co-incide , and are united , then is his Center in the Meridian . If the Sun do not shine clear , as when he is under mist , or a thin cloud , you may exactly take him up in the Meridian , with the two strings . This Frame will serve as well , to know when any of the North Stars comes South , or North , and consequently when they are highest , and when they are lowest : for being fixed in an open place of the Orchard , there 's no Celestial Body can pass the Meridian , either on the one side , or the other , but it may be catched , what ever the Altitude be , and that most easily .

OBSERVATION VIII .

THere hath been much inquiry made by some anent the reason , why the dead body of a man or beast , riseth from the ground of a Water , after it hath been there three or four days . But though many have endeavoured to solve the question , yet the difficulty remains ; and in effect it cannot be answered , without the knowledge of the foregoing Doctrine , anent the nature of fluid Bodies . To find out the reason then of this Phenomenon , consider , that all Bodies , are either naturally heavier then Water , as Stone and Lead , or naturally lighter , as Wood and Timber . If they be heavier , they sink : if they be lighter , they swim . Now I say , a mans body immediatly after he is drowned , his belly being full of Water , must go to the ground , because in this case , it will be found specifically or naturally heavier then Water . That 's to say , a mans body , will be heavier , than as much Water , as is the bulk of a mans body . For pleasing the fancy , imagine a Statue to be composed of Water , with all the true dimensions of the person that 's dead , so that the one shall answer most exactly to all the dimensions of the other . In this case , if you counterpoise them in a Ballance , the real body , that 's made up of flesh , blood , and bones , shall weigh down the other . But after this dead body hath lien a short time among the Water , it presently begins to swell , which is caused by the fermentation of the humors of the blood , which goeth before putrefaction , and after three or four dayes swells so great , that in effect , it becomes naturally lighter than Water , and therefore riseth . That is to say , take that body , that is now swelled , and as much bulk of Water , as will be the precise quantity of it , and having counterpoised them in a Ballance , you will find the Water heavier than the body .

OBSERVATION IX .

UPon Thursday the 25 of August 1670 , the following Experiment was made in a new Coal-sink , on the West side of Tranent . When the Coal-hewers had digged down about 6 or 7 fathom , they were interrupted sometimes with ill Air : therefore to know the power and force of the Damp , we let down within the Bucket a Dog . When he had gone down about 4 fathom , or middle Sink , we found little or no alteration in him , save only that he opened his mouth , and had some difficulty in breathing , which we perceived evidently : for no sooner he was pulled up to the top , where the good Air was , but he left off his gaping . We let him down next to the bottom , where he tarried a pretty while , but no more change we found in him than before . After this we let down a great quantity of Whins , well kindled with a bold flame , but they no sooner came to the middle of the sink , but the flame was in an instant extinguished : and no sooner was the Bucket pulled up , but they took fire again . This was 5 or 6 times tried , with the same success . If we compare this Observation with the first , we will find , that all Damps are not of the same power and force ; but that some are stronger , and kills men and beasts in an instant : and that others are less efficacious , and more feeble , and doth not so much hurt , and that men may hazard to go down into a Sink , where ill Air is , even though fire be sometimes extinguished . We see next , that these Damps doth not alwayes infect the whole Air of a Coal-pit , but only a certain quantity : for sometimes it is found in the bottom , sometimes in the middle . And we see lastly , that they are not alwayes of long continuance : for it is found , that though the Air be ill in the morning , yet it may be good ere night ; and totally evanished ere the next day . We may add , as was noted in the first Observation , that these Damps depend much upon the scituation of the winds , seing in strong Southerly winds , they are frequently in these places .

OBSERVATION X.

OF these many excellent devices , that have been found out of late , the Air-pump is one , first invented in Germany , and afterwards much perfected in England by that Honourable Person Mr Boyl , who for his pains , and industry in making Experiments therewith , deserves the thanks of all learned persons . Several trials hath been made of late by it , some whereof , are as follows . I took a slender Glass-tub about 40 inches long , closs above , and open below , and filled it with Water . I next inverted it , and set the orifice of it , just upon the mouth of the Brass-pipe , that bends upward thorow the board , whereon the Receiver useth to stand , and cemented them together . At the first exsuction , the whole Water in the Pipe fell down , and ran thorow the Brass-conduit to the Pump . Having for a short while stopped the passage , and thrust down the Sucker , I next opened it again , and the Pump being full of Water , it was driven with a considerable force up thorow the Pipe ; yet was it not compleatly fill'd as before , by reason of some Air , that I saw in the top . After this was done , with pleasure five or six times , I opened the Stop-cock more quickly , than I had used , but the Water , by this means , was so furiously driven up thorow the Tub , that in effect , it broke the end of it , that was Hermetically sealed ; and the piece that flew off , did hit the seiling so smartly , that it rebounded a very far way . From this we see the reason , why Water falls not down from Vessels that have narrow necks , though they be inverted , because it 's kept in by the force and power of the environing Air. 'T is observable , that though this Pipe had been 30 foot high , yet the whole Water in it would have subsided , and fallen down , with one exsuction .

The next trial was with the help of a small Receiver , which in effect was a real Cupping-glass . This had a hole made in the bottom of it , and was cemented to the Brass-plate , and the mouth of it looking upward , had a lid for covering of it . I took next the lately mentioned Glass-pipe , and filled it with good Brandy , and having drowned the end of it among stagnant Brandy , I set the Vessel wherein it was within the Receiver , the Pipe coming up thorow the lid , and having cemented it closly , I made the first exsuction , and found no descent of the Liquor from the top of the Tub. At the second , it fell down about an inch . At the third , it fell down four or five . But here appeared a great multitude of small Bubbles of Air , like broken Water , near the top of the Pipe within . And besides this Phenomenon , there ascended from the stagnant Liquor up thorow the Pipe , an infinit number of small Bubbles , no bigger than Pin-heads , for a very large time . With a fourth exsuction , it fell down within two or three inches of the stagnant Brandy . And thinking to make the one level with the other , I made a fifth ; but here appeared a strang effect , namely , not only the whole Brandy in the Pipe subsided , and was mingled with the stagnant Brandy , but at this exsuction , there came a great quantity of Air from the mouth of the Pipe , and rose up thorow the stagnant Liquor in Bubbles . Having made another exsuction , there came yet more Air out , and so copiously , that I thought there had been some seak in the Tub , through which the outward Air had entered ; but knowing the contrary , I continued Pumping a very long time , till I found less and less come out , and at length , after near 30 exsuctions it ceased . This Air to appearance , was so much as might have filled twenty Tubs , every one of them as large , as the Tub it came out of . And surely all of it came out from among the small quantity of Brandy that filled the Pipe , and that environed the mouth of it , I mean the stagnant Brandy , both which would not have been eight spoonful . After this I opened the Stop-cock leasurely to let in the Air to the Receiver ; then did the Brandy climb up the Pipe slowly , till it came near to the top , and there made some little halt , by reason of half an inch of Air that appeared there . But more and more Air coming into the Receiver , that half inch in the top of the Pipe , did so diminish , that it appeared no bigger than the point of a Pin , and was scarcely discernable to the eyes . What a strange and wonderful faculty of dilatation and contraction must be in the Air , seing that which presently had filled the whole Tub , that was 40 inches long , and the sixth part of an inch wide , was contracted to as little room , as the point of a Needle . And by making some new exsuctions , that small Atome of Air did so dilate it self again , that it filled the same Tub , and not only that , but , as formerly , it bubbled out from the mouth of the Pipe several times .

'T is to be observed , that though at the first falling down of the Brandy , it appeared like broken Water , near the top of the Pipe within , yet no such thing was seen the second time it fell down ; the reason is , because by the first exsuctions , it was well exhausted of its aërial particles . Once or twice I found , after the Brandy within the Pipe was well freed of Air , that no exsuctions could make it move from the top of the Tub ; and observed a round Bubble of Air to march up , which when once it came to the top , did separate the one from the other . If this hold good , it seems to prove , that neither Mercury , nor any other Liquor would fall down in Pipes , unless there were Air lurking amongst the parts to fill up the deserted space .

From this Experiment we learn , that no person can well apprehend or conceive , how far , and to what bounds the smallest part of Air is able to expand it self . And it proves evidently , that when the Receiver is as much emptied as it can be , by the Art of man , yet it is full of Air compleatly .

The third trial was after this manner : I set within the Receiver a little Glass half full of Brandy , and the lid being cemented on , I began to pump , but there appeared no alteration at the first exsuction . At the second , I perceived a great company of very small Bubbles , that for a long time ascended from the body of it , and came to the surface . At the third , they were so frequent , and great , that the Brandy appeared to seeth and boil , and by reason of the great ebullitions , much of it ran over the lips of the Glass , and fell into the bottom of the Receiver . This boiling continued for the space of 7 or 8 exsuctions , and by process of time , the Bubbles grew fewer and fewer , and when about 30 or 40 exsuctions were made , no more appeared . With this same sort of Brandy , I filled the fore-named Pipe , and set it within the Receiver , the mouth of the Tub being guarded with the same sort of Liquor . When it began to subside , there appeared no Bubbles near the top as before : the rea●on seems to be , because the Brandy was well exhausted from its aërial particles . For a fourth trial , I filled the same Tub with Ale , that was only 5 or 6 dayes old , and drowning the end of it among stagnant Ale of the same kind , I began to Pump , and found , that assoon as the Liquor began to subside , from the top of the Pipe , the whole Ale within the Pipe , almost turned into Air , and Froth , and so many large Bubbles came up from the stagnant Liquor , that I thought the whole was converted into Air. It was most pleasant to behold their several forms and shapes , their order and motion . This same Tub being filled with sweet milk , I found very few Bubbles in it , when by the exsuctions , it began to subside . I likewise took a little Glass-viol , and fill'd the half of it full with common Ale , and set it within the Receiver . At the first exsuction , Bubbles of Air began to rise out of it . At the second and third , they did so multiply , that they fill'd the other half of the Glass , and ran over , as a Pot doth when it boileth . And before I could exhaust all the Air out of it , moe than 20 exsuctions passed .

For a fifth trial , I filled the often mentioned Pipe with Fountain-water , and when it began to subside by Pumping , I found it leave much Air behind it . But all the exsuctions I made , could not make the Water of the Pipe go so low , as the stagnant Water , by which impediment , I could Pump no Air out of the Pipe , as I did , while I made use of Brandy . This tells us , that either there is not so much Air lurking among Water , as among Brandy , or that the Air among this , hath a more expansive faculty in it , than the Air that lurks among Water . If any think , that it is not true and real Air , which comes from the Brandy , but rather the Spirits of it , which evaporats . I answer , if a man tast this Brandy that 's exhausted of its aërial particles , he will find it as strong , as before , which could not be , if the Spirits were gone ,

For a sixth trial , I took a Frog and inclosed her within the Receiver . But all the exsuctions I was able to make , could not so much as trouble her . Only , when the Receiver was exhausted , I perceived her sides to swell very big , and when the Stop-cock was turned , to let in the Air again , her sides clapped closs together . I observed likewise , when the Air was pretty well Pumped out , that the Frog had no respirations , or if there were any , they were very insensible . The next day , after she had been prisoner in the Receiver 24 hours , I began again to Pump , and after several exsuctions , her sides swell'd pretty great , and I perceived her open her mouth wide , and somewhat like a Bag endeavouring to come out , which surely hath been some of her noble parts , striving to dilate themselves , the body being freed of all Pressure from the ambient Air.

OBSERVATION XI .

TAke a slender chord , about 4 or 5 yards in length , and fasten the middle of it to the seiling of a Room with a nail , so that the two ends of it may hang down equally . Take next a piece of Wood , two or three foot long , two inches broad , and one inch thick , and boring an hole in each end of it , put through the two ends of the chord , and fasten them with knots ; but so , that the piece of Wood may ly Horizontal , and be in a manner a Pendulum to swing from the one end of the Chamber to the other . Take next a Bullet of Lead or Iron , about 20 or 24 ounces , and lay it upon the said piece of Wood : but because it cannot well ly , without falling off , therefore nail upon the ends , and the sides of the Timber , four pieces of Sticks , on each end one , and on each side one , as Ledgets , for keeping the Bullet from falling off . All things being thus ordered , draw up the piece of Wood towards the one side of the Room , by which means losing its horizontal position , it will ly declining-wise , like the roof of an house . In this position , lay the Iron Bullet in the upmost end of it , and then let them both pass from your fingers , the one end of the Wood going foremost , and you will find it swing towards the other side of the house , and return again , as a Pendulum . This motion , if the Wood be well guided in its vibrations , will last perpetually , because in its moving down , the Bullet is hurled from the one end of the Wood , to the other , and hits it so smartly , that it begets in it , an impulse , whereby it is carried farder up , than it would be , without it . By this means , the vibrations get not liberty to diminish , but all of them are kept of the same length . In the second vibration , the same Bullet is hurled back again to the other end , and hiting it with all its weight , creats a second impulse , wherewith the Wood is carried , as far up as the point it was first demitted from .

Though this may seem a pretty device to please the fancy , that 's many times deceived , while things are presented to it , by way of speculation , yet upon tryal and experience , there will be found , an unspeakeable difficulty : and it 's such an one , that a man would not readily think upon . I said , that when the Wood was let go , and was in passing down , the Bullet in it , would hurl down , and hit the oppsite end , and beget an impulse ; but there is no such thing , for verily , though the Bullet be laid upon a very declining plain Board , whereupon no man could imagine a round body could ly , yet all the time the Board is in swinging , from the one side of the Chamber , to the other , and consequently , sometimes under an horizontal , and somtimes under an declining position , the Bullet lies dead in the place , where you first placed it . This Observation is not so much for a perpetual motion , as for finding out the reason of this pretty Phenomenon , namely , what 's the cause , why the Bullet , that cannot ly upon a reclining Board , while it 's without motion , shall now ly upon it , while it 's under motion ? What is more difficult , and nice , to ly upon any thing , that declines from a levell , than Quick-silver ; yet lay never so much of it upon this Board , while it is swinging , it shall ly dead , and without motion . But no sooner you stop the motion of the wood , but assoon , the Bullet , or the Quick-silver , is hurled , either this way , or that way .

OBSERVATION XII .

I Find it mentioned by some learned persons , that when a Ship is under Sail , if a stone be demitted from the top of the Mast , it will move down in a line parallel with it , and fall at the root . Some might think , it ought not to fall directly above the place it hang over , but rather some distance behind , seing the Ship hath advanced so much bounds , in the time , wherein the stone is coming down . Likewise , while a Ship is under Sail , let a man throw up a stone never so high , and never so perpendicular , as to his apprehension , yet it will fall down directly upon his head again , notwithstanding that the Ship hath run ( perhaps ) her own length in the time , while the stone was ascending and descending . This experiment I find to hold true , which may be easily tryed , especially when a man is carried in a Boat upon smooth Water , drawn by a horse , as is done in some places abroad . Let him therefore throw up a little Stone , or any heavy Body , and he will find it descend just upon his head , notwithstanding that the Horse that draggs the Boat , be under a gallop , and by this means hath advanced ten or twelve paces in the time . Or while the Boat is thus running , let a man throw a stone towards the brink of the Water ; in this case he shall not hit the place he aimed at , but some other place more forward . This lets us see , that when a Gun is fired in a Ship under Sail , the Bullet cannot hit the place it was directed to . Neither can a man riding with a full Career , and shooting a Pistol , hit the person he aims at , but must surely miss him , notwithstanding , that though in the very instant of time wherein he fires , the mouth of the Pistol was most justly directed . For remedy whereof , allowance must be granted in the aiming at the mark .

While a man throws up a stone in a Ship under Sail , it must receive two distinct impulses , one from the hand , whereby it is carried upward , the other from the Ship , whereby it is carried forward . By this means , the stone in going up , and coming down , cannot describe a perpendicular , but a crooked Line , either a Parabola , or a Line very like unto it . Neither can it describe a perpendicular Line , in coming down from the top of the Mast , though in appearance it seem to do so , but a crooked one , which in effect must be the half of that , which it describes in going up , and coming down . For this same cause , a stone thrown horizontally , or towards the brink of the Water , must describe a crooked Line also . And a Pistol Bullet shot , while a man is riding at a full Carreer , must describe a Line of the same kind . Note , that a man walking from the Stern of a Ship to the Head , walks a longer way , than in walking from the Head to the Stern . Secondly , a man may walk from the Head to the Stern , and yet not change his place . 'T is observable , that a man under board , will not perceive whether the Ship be sailing , or not , and cannot know when her Head goes about . And it is strange , that when a man is inclosed in a Hogs-head , though he have light with him , yet let him be never so oft whirled about , he shall not know , whether he be going about , or not .

OBSERVATION XIII .

I Found in a Philosophical transaction lately Printed , that Decemb. 13. 1669 , one Doctor Beal found the Mercury in the Baroscope , never to be so high , as it was then . That same very day , I found the hight of it 29 inches , and nine ten parts , which I never observed before . And though the day here was dark , and the Heavens cove●ed with Clouds , yet no rain for many dayes followed , but much dryness , and fair weather . On Saturday night , March 26 , 1670 , I found the altitude no more than 27 , and nine ten parts . This night was exceeding windy , with a great rain . On February 1. 1671. I found the altitude 30 inches , and the Heavens most clear . But in the most part of May following , I have found the hight but 27 inches , and five ten parts , in which time there was abundance of rain .

OBSERVATION XIV .

NOvember 7. 1670. I made exact trial , with the Magnetick Needle for knowing the variation , and I found it vary from the North , three degrees and a half , towards the West . Hevelius writes from Dantzick to the Royal Society at London , Iuly 5. 1670 , that it varies with him seven degrees twenty minuts , west .

OBSERVATION XV.

DEcember . 17. 1669 , I observed with a large Quadrant , half 9 a clock at night , the formost Guard-star , when it was in the Meridian , and lowest , to have 41 degrees 22 minuts of altitude . And on Ianuary 7. 1670 at 7 a clock in the morning , I found it , when it was in the Meridian , and highest , to have 70 degrees , 27 minuts Hence I conclude the elevation of the Pole here to be 55 degrees , 54 minuts , 30 seconds : and consequently as much at Edinburgh ; because both the places are upon one and the same Parallel .

OBSERVATION XVI .

FOr finding the true Meridian , follow this method . In some convenient place fix two Wyre strings with weights at them , that they may hang perpendicular . Then in the night time , observe , when the fourth star of the Plough begins to come near to the lowest part of the Meridian , at which time you will find the Polar star highest . Then , so order the two strings , by moving them hither , and thither , till both of them cover both the said Stars , then shall they in that position give you the true South and North. This observation is the product of the seventh .

OBSERVATION XVII .

THere fell out in Mid and East-Lothian , on Thursday May 11 , 1671 , in the afternoon , a considerable shour of hail , with thunder and rain . It came from the South-west , with a great blast of wind , and ran alongs from Picts-land-hills North-east , towards the Sea-coast . The hail were big in several places , as Musquet Ball , and many of them rather oval than round . Some persons suffered great loss of their young Pease ; others of their Glass Windows . Eight or ten days before , there was a considerable heat , and dry Weather . For 20 dayes after , cold Easterly winds , with rain every day , but especially , in the end of the Moneth , extraordinary rain and mist. This is so much the more to be observed , because in this Countrey , seldom such extraordinary hail falls out . This year the Agues and Trembling Fevers have been most frequent , and to many deadly .

OBSERVATION XVIII .

I Did hear lately of a curious Experiment in Germany , made by a Person of note , which I shall briefly in this Observation , let the Reader understand . And though I have heard since , that it is now published in Print , yet I hope it will not be impertinent to mention it here , especially for their cause , who cannot conveniently come to the knowledge of such things . And for this reason also , that I may explicat the Phenomena thereof , from the foregoing doctrine , and demonstrat particularly the true cause of that admirable effect , that 's seen in it , which I desiderat in the publisher . The Auctor then takes two Vessels of Brass , each one of them in form of half a sphere , of a pretty large size . Nothing can more fitly represent them for form and quantity , than two Bee-skeps . Only , each of them , hath a strong Ring of Brass upon the Center without : and they are so contrived by the Artist , that their orifices agree most exactly , so that when they are united , they represent an intire Sphere almost . In one of the sides , there 's a hole , and a Brass Spigot in it , through which the whole Air within , is exsucted , and drawn out , namely by the help of the Air-pump . And , when by several exsuctions the Vessels are made empty , the Stop-cock is turned about , by which means , no Air can come in . And , they remaining empty , are taken from the Pump , and do cleave so fast together , that though a number of lusty fellows , 12 on each side , do pull vigorously , by help of ropes fastned to the Rings , yet are they not able to pull them asunder . And because this will not do it , he yokes in 12 Coach Horses , six on every side , yet are they not sufficient , though they pull contrariwise to other , to make a separation . But to let the Spectators see , that they may be pulled asunder , he yokes in 9 or 10 on every side , and then after much whipping , and sweating , they pull the one from the other .

The cause of this admirable effect , is not the fear of vacuity , as some do fancy , for if that were , all the Horses in Germany would not pull them asunder , no not the strength of Angels . It must then be some extrinsick weight and force , that keeps them together , which can be nothing else , but the weight of the invironing Air. Because , no sooner a force is applied , that 's more powerful , than the weight of the Air , but assoon they come asunder . And so neither six men , nor six horses on each side are able to do it : but nine or ten on each side makes a separation . For understanding the true cause of this Phenomenon , we must consider that the Vessels are 18 inches in diameter . If this be , then according to the last Experiment , there are two Pillars of Air , each one of them as heavy as a Pillar of Mercury 18 inches thick , and 29 inches long , by which they are united . Or , each Pillar of Air , is as heavy , as a Pillar o● Water 34 foot high , and 18 inches in diameter . For finding the weight of it in pounds , and consequently , the weight of each Pillar of Air , by which the two Vessels are united , follow this method . First , multiply 9 the semidiameter of the Pillar , by 54 the circumference , and this gives you 486 , the half whereof is the bounds of the Area , namely 243. And because 34 foot contains 408 inches , I multiply 408 by 243 , the product whereof is 99144 ; so many square inches are in a Pillar of Water 34 foot high , and 18 inches thick . Now seing there are 1728 inches in a cubical foot , I divide the number 99144 , by this number , and I find 57 square foot of Water , and more . And because every square foot weighs 56 pound Trois , I multiply 56 by the number 57 , and the product is 3192 pound , which is the just weight of a Pillar of Water 34 foot high , and 18 inches in diameter , and which is the just weight also of each Pillar of Air , by which the two Vessels are kept together , which will be more weight than seven Hogs-heads full of Water . This is easily known ; for seing a quart of our measure weighs seven pound , ( or to speak strictly six pound fourteen ounces , seing the Standard-jug of Striviling contains three pound seven ounces of Water ) a gallon must weigh 28 pound : but 16 times 28 , is 448. A Puncheon then full of Water , weighs 448 pound . If then you divide 3192 by 448 , you will find more than 7. The 9 horses then upon this side have 3192 pound weight to draw , or 199 stone , or the weight of seven Hogs-heads full of Water . The other 9 horses upon the other side , have as much to pull . 'T is no wonder then to see so much difficulty and pains to make a separation . It is observed , that before the Air be exsucted and drawn out of the two Vessels , one man is able to pull them asunder with his hands only . Nay , which is more , if he but blow into them , as a man doth into a Bladder , he will separat them . The reason is , because the Air within , is of as great force , as the Air without . 'T is observable next , that the larger the Vessels be in diameter , the more strength is required to pull the one from the other . Upon supposition then , they were 4 foot wide , I verily believe 30 yoke of oxen , upon every side , would hardly disjoyn them ; because the weight of each Pillar of Air , would be no less , than 22844 pound , which would take 63 strong horses to overcome the force of it . To pull the one Vessel therefore from the other , there must be 126 horses , that is , 63 on every side .

OBSERVATION XIX .

THough this Observation may seem useless , because the Proposals , that are mentioned in it , cannot be made out , and brought to pass , the Author having died , before he had encouragment to prosecute them : yet for these following reasons , I have adventured to insert it here . First , that others , may either be minded to find out ( if possible ) his inventions , or set a work to find out somethings , that may be as useful . Next , because , he was one of this same Nation , and a great Master of the Mathematicks , not only in the Speculative , but in the Practical part chiefly , and admirable for invention . And for this cause principally I have presumed to mention his designs , and proposals , which were found among his Notes , after his death , which are here insert , as they were written with his own hand , and offered to the publick , not only at home , but abroad to strangers . There have been men in all ages famous , for some one Art and Science beyond others , as Apelles for Painting , Hippocrates for Medicine , Demosthenes for Oratry , but who have been more famous in their time than some persons for their profound knowledge in Astronomy , Geometry , and the other parts of the Mathematicks . What an admirable person was Archimedes for his divine knowledge , both in the Speculative , and Practical part . Yet , it was not his speculations simply , though excellent , that did so much commend him , as his Inventions , and admirable Engines for peace and war , as is clear from the Romane Histories , and others . I confess the Students of these Arts , are not so much in request now , at least amongst some , and that knowledge is not so much esteemed ; and the reason may be ; because some who profess themselves great Masters , study nothing but the pure speculations , which sometimes are to small purpose , others before knowing the same , unless for perfecting of the mind , and giving to a man some private satisfaction . But such things will never commend a man so much as the practical part , and new Invention will do . 'T is surely a small business for one to do nothing , but to nibble at some petty Demonstration . But when such speculations are joyned with invention and practice , for the profit , and use of men , among whom they live , then are they far more to be commended . And if this be not , such knowledge is of small advantage to themselves or others . Many of the Ancient , and late Astronomers have been , and are famous for practice , as witness the indefatigable pains they have been at in making their Observations . What hath so highly commended Merchiston over all Europe , as his inventions , especially his Logarithmes ? And if all be true , that 's reported ( which I am apt to believe ) he might have been more renowned , for his many excellent Engines , which though useful , yet because hurtful to mankind , he buried with himself . I am confident , if the Author of these proposals had had time to have prosecuted them , he would have been celebrated in the Catalogue of the most famous Mathematicians of his time . But leaving this , I shall give you them in his own words : but first his Apology .

These bold proposals will need perhaps an apology to such , to whom the causes , and circumstances are unknown . Let it suffice , that the Proposer finding himself between two extreams , either to leave unprosecuted this affair , for fear of being mistaken by some , as impudent , or to commit himself openly to the charitable judgement of others , who will suspend their censure , till they have seen what his endeavours will produce . He hath rather chosen this last , especially considering , that his silence could not answer to his duty , which he owes to his Countreys service , seing the following Engines may be so useful to it . A deduction of the fabrick , causes , and occasions of these new Engines , that set the Inventer a-work , would take a long time to discourse upon . This Paper therefore is only destined for a short informat●on of their use , the rest , which could not here be insert without impertinency , may be supplied afterwards ( if need be ) either by a discourse , or by a particular demonstration . The Proposer then is of opinion , ( if self-love of his own Inventions do not blind his Judgement ) that these paradoxes may be truly affirmed .

That if it shall please His Majesty to arm with these new Arms , and Engines , 5000 Foot , or fewer , this small number shall be Masters of the Fields in France , Germany , Spain , or where else it shall please His Majesty , however encountered by the most powerful Army of Horse or Foot , armed with ordinary Arms , of Pistol , Carabine , Pike , Musquet , which Europe can bring to the Fields .

The cause of this admirable effect , is in the quality of these new Arms , by which , the whole Horsemen and Footmen of the enemy are rendred useless , and unservicable ; neither can they do any offence to these , who are so armed .

The Musquetteers , who can only serve against these Machins , shall be put to such disadvantage , as it is impossible they can stand , the least time , in the common way of service with the Musquet , it not being able to make one shot for twenty , which shall be made from these new Engines .

These new Arms , have this advantage likewise , that these who are so armed , can by no force of Horse or Foot be broken , or put to disorder . The Souldiers are also by them put to a necessity of keeping together , and fighting , and by them , they are so Baricado'd , and strongly defended , that if they leave them not , they cannot be exposed to danger . This contributes much to good Discipline , when the Souldiers shall by necessity be tied to his duty , and fear , which otherwise makes him run away , shall here for his safety make him stand .

These new Arms are useful , as well in Marching , as in Combating , for with them , we may march securely two in front , through the straitest passages , and be able to force with them any advantage a strait passage can give to an enemy . Besides , for a long hasty march , where Victuals cannot be well carried , the Souldiers are able with these Arms to carry their own provision for eight dayes , with more facility , then they can now carry one dayes provision .

To lodge in the open fields , these Arms shall need no Intrenching , for they sufficiently both Arm and Baricade the Souldiers .

And as they are useful in Service , so are they a great deal cheaper than the ordinary Arms. For although with 5 thousand men so armed , the service of 100000 armed with common Arms may be done , yet the whole price of them will not amount to that which will be required for arming 20500 Corrassiers , as may be particularly deduced , from the particular prices of the Arms , and Engines fitted for the service of 5000 men . The Proposer doth offer to shew , that these Arms will not surmount 40000 pound Sterling . The Artillery will amount to 4500 , and the payments of this number of men so armed , yearly to 70000 pound . Yet all these are taken in so large a latitude of reckoning , as the sum of Arms , Artillery , and payments , will not be much above 130000 pound Sterling .

The Arms from which this effect is promised , are new Engines , with which one man is able to do the service of a great many Musquetteers . And those are of two sorts , either to be used upon a small Wagon for Footmen , or on a greater for a Horse , with either of which , one hand is able to make the fire of 100 Musquetteers , and so much better , by how much it is more regularly , and fitly done for execution and offence . The new Cannon shall have the like advantage above the old , both for easie carriage , being lighter , and for greater execution , shooting six , nine , or twelve Bullets for one . These Arms give not only this advantage at Land in the field , but also in Ships , and places of defence .

These nine following propositions he likewise offered to make good ,

First , With one shot of Cannon , to do the execution of five shot of the same Cannon , in the common way of Battery .

Secondly , to disable any Ship or Galley with one shot of Cannon .

Thirdly , to fire any combustible matter with the shot of a Cannon .

Fourthly , to make an Machin or Engine for transporting an Army , which may be carried without the incommodity thereof .

Fifthly , to make a flotting Fortress for defence of Rivers , and prohibition of Passages .

Sixthly , to make a Mortar that hath a directory Stell upon the Carriage .

Seventhly , to make Petards of divers forms , that shall be able to do twice as much execution , as those that contain as much Powder .

Eighthly , to make small Petards of great effect .

Lastly , to make Bridges , and Scaling Ladders of easie Carriage .

OBSERVATION XX.

THese Observations being Miscellany , require not a formal connexion between themselves , and therefore 't is no matter what method I keep in setting them down . And though this may seem not so pertinent , as others , yet because the design of it is only Philosophical , and for advancing the Historical part of Learning in order to Spirits , upon which the Scientifical part doth so much depend , I have presumed to insert it here , considering also that there are some , who have adventured to deny their existence , and being ; which from such a History as this , may be more than probably evicted . I find likewise , that several Writers have remarked such strange accidents , and have transmitted them to posterity , which may serve for good use . The subject-matter then of this Observation , is a true and short account of a remarkable trial , wherewith the Family of one Gilbert Compbel , by Profession a Weaver in the old Paroch of Glenluce in Galloway , was exercised . Though the matter be well known to several persons at that time , and since too ; yet there are others , eighteen years interveening , to whom ( perhaps ) such a relation will not be unacceptable , who have either not as yet heard of it , or at least , have not gotten the true information , which is here set down , as it was Written , at the desire of a special Friend , by Gilbert Campbel's own Son , who knew exactly the matter , and all the circumstances , whose words are as follows .

It happened in October 1654 , that after one Alexander Agnew , a bold and sturdy Beggar , who afterwards was hanged at Dumfreis for blasphemy , had threatned hurt to the Family , because he had not gotten such an alms as he required : the said Gilbert was oftentimes hindered in the exercise of his Calling , all his Working-Instruments being some of them broken , some of them cutted , and yet could not know by what means this hurt was done ; which piece of trouble did continue , till about the middle of November , at which time the Devil came with new and extraordinary assaults , by throwing of Stones in at Doors and Windows , and down thorow the Chimney-head , which were of great quantity , and thrown with great force , yet by Gods good providence , there was not one person of the Family hurt , or suffered dammage thereby . This piece of new and sore trouble , did necessitat Mr. Campbel to reveal that to the Minister of the Paroch , and to some other Neighbours and Friends , which hitherto he had endured secretly . Yet notwithstanding of this , his trouble was enlarged ; for not long after , he found oftentimes his Warp and Threeds cut , as with a pair of Sizzers , and the Reed broken : and not only this , but their apparel cut after the same manner , even while they were wearing them , their Coats , Bonnets , Hose , Shooes , but could not discern how , or by what mean . Only it pleased God to preserve their persons , that the least harm was not done . Yet , in the night time , they wanted liberty to sleep , something coming , and pulling their Bed-cloaths and Linnings off them , and leaving their bodies naked . Next , their Chests , and Trunks were opened , and all things in them strawed here and there . Likewise , the parts of the Working Instruments , that had escaped , were carried away , and hid in holes and bores of the house , where hardly they could be found again . Nay , what-ever piece of Cloath , or Houshold-stuff , was in any part of the house , it was carried away , and so cut and abused , that the Good-man was necessitated with all haste and speed , to remove , and to transport the rest to a Neighbours house , and he himself compelled to quite the exercise of his Calling , whereby only he maintained his Family . Yet , he resolved to remain in the house for a season . During which time , some persons about , not very judicious , counselled him to send his children out of the Family , here and there , to try whom the trouble did most follow , assuring him , that this trouble was not against all the Family , but against some one person , or other in it , whom he too willingly obeyed . Yet , for the space of four or five dayes after , there were no remarkable assaults , as before . The Minister hearing thereof , shewed him the evil of such a course , and assured him , that if he repented not , and called back his children , he might not expect that his trouble would end in a right way . The children that were nigh by , being called home , no trouble followed , till one of his sons , called Thomas , that was farrest off , came home . Then did the Devil begin afresh ; for upon the Lords Day following , in the afternoon , the house was set on fire , but by his providence , and the help of some people , going home from Sermon , the fire was extinguished , and the house saved , not much loss being done . And the Monday after , being spent in privat Prayer and Fasting , the house was again set on fire upon the Tuesday about nine a Clock in the morning , yet by providence , and the help of Neighbours , it was saved , before any harm was done .

Mr. Campbel , being thus wearied , and vexed , both in the day , and in the night time , went to the Minister , desiring him , to let his son Thomas abide with him for a time , who condescended , but withal assured him , that he would find himself deceived , and so it came to pass : for , notwithstanding that the child was without the family , yet were they , that remained in it , sore troubled both in the day time , and in the night season , so that they were forced to wake till mid-night , and sometimes all the night over . During which time , the persons within the Family , suffered many losses , as the cutting of their Cloaths , the throwing of Peits , the pulling down of Turff , and Feal from the Roof , and Walls of the House , and the stealing of their Apparel , and the pricking of their flesh and skin with Pins . The Presbytery having conveened at the place , for a solemn Humiliation , perswaded Gilbert Campbel to call back his Son Thomas , notwithstanding of whatsoever hazard might follow . The Boy returning home , affirmed that he heard a voice speak to him , forbidding him to enter within the house , or into any other place where his Fathers Calling was exercised . Yet he entered , but was sore abused , till he was forced to return to the Ministers house again .

Upon Monday the 12 of February , the rest of the Family began to hear a voice speak to them , but could not well know from whence it came . Yet , from evening till midnight , too much vain discourse was kept up with the Devil , and many idle and impertinent questions proposed , without that due fear of God , that should have been upon their Spirits , under so rare and extraordinary a trial . The Minister hearing of this , went to the house upon the Tuesday , being accompanied with some Gentle-men , who after Prayer was ended , heard a voice speaking out of the ground , from under a bed , in the proper Countrey Dialect , saying , Would ye know the Witches of Glenluce ? I will tell you them ; and so related four or five persons names , that went under an evil report . The said Gilbert informed the company , That one of them was dead long ago . The Devil answered , and said , It is true , she is dead long ago , yet her spirit is living with us in the world . The Minister replied , saying , ( though it was not convenient to speak to such a person ) . The Lord rebuke thee Satan , and put thee to silence ; we are not to receive any information from thee , whatsoever fame any persons go under . Thou art but seeking to seduce this Family : for Satans Kingdom is not divided against it self . After which all went to Prayer again , which being ended ( for during the time of Prayer no trouble was made ) the Devil with many threatnings boasted and terrified the Lad Thomas , who had come back that day with the Minister , that if he did not depart out of the house , he would set all on fire . The Minister answered , and said , The Lord will preserve the House , and the Boy too , seing he is one of the Family , and hath Gods warrand to tarry in it . The Devil answered , He shall not get liberty to stay : he was once put out already , and shall not abide here , though I should pursue him to the end of the world . The Minister replied , The Lord will stop thy malice against him . And then they all prayed again , which being ended , the Devil said , Give me a Spade and a Shovel , and depart from the house for seven dayes , and I shall make a grave , and ly down in it , and shall trouble you no more . The Good-man answered , Not so much as a Straw shall be given thee , through Gods assistance , even though that would do it . The Minister also added , God shall remove thee in due time . The Devil answered , I will not remove for you , I have my Commission from Christ to tarry , and vex this Family . The Minister answered , A permission thou hast indeed , but God will stop it in due time . The Devil replied , I have ( Mes. Iohn ) a Commission , that ( perhaps ) will last longer than your own . After which , the Minister and the Gentlemen arose , and went to the place where the voice seemed to come from , to try if they could find any thing . And after diligent search , nothing being found , the Gentlemen began to say , We think this voice speaks out of the children , for some of them were in their beds . The Devil answered , You lie , God shall judge you for your lying , and I and my Father will come and fetch you to hell , with Warlock-theeves ; and so the Devil discharged the Gentlemen to speak any , saying , Let him speak that hath a Commission ( meaning the Minister ) for he is the Servant of God . The Gentlemen returning back with the Minister , they sat down near to the place whence the voice seemed to come from , and he opening his mouth , spake to them , after this manner . The Lord will rebuke this Spirit , in his own time , and cast it out . The Devil answering , said , It is written in the 9 of Mark , the Disciples could not cast him out . The Minister replied , What the Disciples could not do , yet the Lord having hightned the Parents faith , for his own glory did cast him out , and so shall he thee . The Devil replied , It is written in the 4 of Luke , And he departed , and left him for a season . The Minister said , The Lord in the dayes of his humiliation , not only got the victory over Satan , in that assault in the wilderness , but when he came again , his success was no better , for it is written , Joh. 14. Behold the Prince of this world cometh , and hath nothing in me ; and being now in glory , he will fulfill his promise , and God shall bruise Satan under your feet shortly , Rom. 16. The Devil answered , It is written , Mat. 25. There were ten Virgins , five wise , and five foolish ; and the Bridegroom came : The foolish Virgins had no Oyl in their Lamps , and they went unto the wise to seek Oyl ; and the wise said , Go and buy for your selves : and while they went , the Bridegroom came , and entered in , and the door was shut , and the foolish Virgins were sent to hells fire . The Minister answered , The Lord knows the sincerity of his servants , and though there be sin and folly in us here , yet there is a fountain opened to the house of David for sin and for uncleanness , and when he hath washed us there , and pardoned all our sins , for his Names sake , he will cast the unclean spirit out of the land . The Devil answered and said , That place of Scripture is written in the 13 of Zechariah , In that day I will cause the Prophets , and the unclean spirit , pass out of the land ; but afterwards it is written , I will smite the Shepherd , and the Sheep shall be scattered . The Minister answered and said , Well are we , that our blessed Shepherd was smitten , and thereby hath bruised thy head ; and albeit in the hour of his sufferings , his Disciples forsook him , Mat. 26. yet now having ascended on high , he sits in glory , and is preserving , gathering in , and turning his hand upon his little ones , and will save his poor ones in this Family from thy malice . The Minister returning back a little , and standing upon the floor , the Devil said , I knew not these Scriptures , till my Father taught me them . I am an evil Spirit , and Satan is my Father , and I am come to vex this house ; and presently there appeared a naked hand , and an arm , from the elbow down , beating upon the floor , till the house did shake again ; and also the Devil uttered a most fearful and loud cry , saying , Come up Father , come up : I will send my father among you . See , there he is behind your backs . The Minister said , I saw indeed an hand , and an arm , when the stroak was given , and heard . The Devil said to him , Saw you that ? It was not my hand , it was my fathers ; my hand is more black in the loof . Would you see me ? Put out the candle then , and I shall come butt the house among you like fire-balls . After which all went to Prayer , during which time , it did no harm , neither at any other time when God was worshipped . When Prayer was ended , the Devil answered and said , Mes John , if the Good-mans sons prayers at the Colledge of Glasgow , did not prevail more with God , than yours , my father and I had wrought a mischief here ere now . To which one of the Gentlemen replied , though a check had been given him before , Well well , I see you confess there is a God , and that prayer prevails with him , and therefore we must pray to God , and will commit the event to him . To which the Devil replied , Yea Sir , you speak of prayer , with your broad lipped Hat ( for the Gentleman had lately gotten a new Hat in the fashion with broad lips ) I 'le bring a pair of Shears from my father , that shall clip the lips of it a little .

The night now being far spent , it was thought sit every one should withdraw to his own home . Then did the Devil cry out fearfully , Let not the Minister go home , I shall burn the house if he go ; and many other wayes did he threaten . And after the Minister was gone forth , the Good-man being instant with him to tarry , whereupon he returned , all the rest of the company going home . Then said the Devil to the Minister , You have done my bidding . Not thine , answered he , but in obedience to God , have I returned to bear this man company , whom thou dost afflict . Then did the Minister call upon the Name of God , and when Prayer was ended , he discharged Mr. Campbel , and all the persons of the Family , from opening their mouth , in one word to the evil spirit , and when it spake , that they should only kneel down , and speak to God . The Devil then roared mightily , and cryed out , What ? Will ye not speak to me ? I shall burn the house , I shall strike the bairns , and do all manner of mischief . But after that time , no answer was made to it , and so for a long time no speech was heard . After this , the said Gilbert suffered much loss , and had many sad nights , not two nights in one week free ; and thus it continued till April . From April to Iuly , he had some respite , and ease . But after , he was molested with new assaults : and even their Victuals were so abused , that the Family was in hazard of starving ; and that which they did eat , gave them not the ordinary satisfaction they were wont to find .

In this sore and sad affliction , Mr. Campbel resolved to make his address to the Synod of Presbyters , for advice and counsel what to do , which was appointed to conveen in October 1655 , namely whether to forsake the house and place , or not ? The Synod by their Committee , appointed to meet at Glenluce in Feb. 1656 , thought fit , that a solemn Humiliation should be kept thorow all the bounds of the Synod , and amongst other causes , to request God in behalf of that poor afflicted Family , which being carefully done , the event was , through the Prayers of his People , that his trouble grew less till April , and from April to August , he was altogether free . About which time , the Devil began with new assaults , and taking the ready meat that was in the house , did sometimes hide it in holes by the door-posts , and at other times did hide it under the beds , and sometimes among the Bed-cloaths , and under the Linnings ; and at last , did carry it quite away , till nothing was left there , save Bread and Water to live by . After this , he exercised his malice and cruelty against all the persons of the Family , in wearying them in the night time , with stirring and moving thorow the house , so that they had no rest for noise , which continued all the moneth of August after this manner . After which time , the Devil grew yet worse , and began with terrible roarings , and terrifying voices , so that no person could sleep in the house , in the night time , and sometimes did vex them with casting of stones , striking them with staves on their beds in the night time : and upon the 18 of September , about midnight , he cried out with a loud voice , I shall burn the house ; and about three or four nights after , he set one of the beds on fire ; which was soon extinguished , without any prejudice , except the bed it self : and so he continued to vex them .

OBSERVATION XXI .

I Need not make any apology for inserting this Observation , even though it be well known upon the matter in this place . But because the thing is extraordinary , and that there are many who have not so much as heard of it , I have therefore presumed to mention it here . The matter is shortly this . There 's a certain Woman , named Mistris Low , who had a real and true Horn , growing upon the right side of her Head , three inches above her right Ear. The length of it is eleven inches , and two inches about . The form is crooked spirally . It is convex on the outer side , and somewhat guttered in the inner side . It is hard and solid , and all very near of the same greatness . It is not hollow within , as horns are ordinarily , but full , yet it seems to be spongious as a Cane is . It was seven years in growing , and was cut off in May 1671 , by Mr. Temple , an expert Chirurgeon here at Edinburgh .

OBSERVATION XXII .

THis Observation is for finding the Primum vivens in Animals . Albeit I doubt not but the red Spirit , or Blood , in most Terrestrial Animals , is the first product of the Primigenial juice , and therefore not improperly named the true Callidum Innatum of these Creatures , by the Noble and Ingenious Harvey , in his Book de Generatione . Neither do I scruple to yeeld , that the Heart , and appendent Vessels , are the first formed , and perfected parts in the hotter kind of Animals : yet I am confident to affirm , that in many of the colder , and moister kinds of Aquaticks , if not in all , neither the redness and heat of the Vital Spirits , nor the formation of the Heart , Liver , &c. are previously requisite , to the structure and existence of the other parts ; seing the light of life , which at first inhabited the clear and Cristalin radical moisture , before the formation of any particular part , doth alwayes move in every living creature , according to their particular exigency , without any absolute dependency upon any one part , or member ( excepting singular conditions , wherein they may be stated ) as to its substance , light , and motion : there being in some Animals a simple undulation , in others a slow creeping , but in the more perfect , an impetuous running , or rather flying of the Vital Spirits , necessarily required for illumination and vivification of the whole .

For confirmation , I shall give you this singular Experiment . About the middle of March , the sperm of Frogs ( according to the number of Prolifick Eggs therein contained ) sends forth a multitude of small round Creatures , covered with a black , and moveable Frock , which about the end of March , and beginning of April , by the Gyrations of a Tail behind , like a Rudder , do slowly move their bodies in the Water . At this time having opened severals of them , I found nothing ( apparent to the naked eye ) but a clear th●n Membran , under the fore-named black Frock , within which were contained a clear Water , and some small Fibres like Intestines , and in the fore-part a small orifice like a mouth . About the middle of April , its motion is more vigorous , and the Tripes within are most evident , lying in a very fine circular order , but as yet , there is no Vestige of Heart , Blood , or Liver , &c. About the middle of May , the feet formed like small threeds , appear thorow the black Coat : within the Breast , the Heart is then visible , of a white and Fibrous substance , the Liver is white , and the Gall therein easily discerned . But ( which is the head of this Experiment ) the Vital Spirit , in form of a clear and pure Water , is manifestly received by the Nervous Heart , and by the contraction thereof transmitted to all the Body , thorow white transparent Vessels , which being full of this Liquor , do represent the Lymphatick , rather than the Sanguiferous Veins . Last of all do the Pneumatick Vesicles ( which in this Amphibium supply the place of the Lungs ) arise in the Breast , after whose production , the Lympid and Crystalin Liquor , while the Heart is turgid therewith , seems to be red and fiery , but in the other Vessels , it is of a faint pale colour , untill ( about , or near the end of Iune ) the Frock being cast off , and a perfect Frog formed , the whole Vessels are full of Blood , or a red substance very thin , and clear : the Liver , and Pneumatick Vesicles , &c. become red , and Rosy ; so that the Blood in this Amphibium ( which in the more perfect Animals is first compleat ) seems to be the last part in attaining its perfection .

That Salmonds , and great Trouts have an aqueous liquor which runs thorow their Arteries , and Veins , before their Blood attain the true consistency , and saturat tincture I am certain : whether it hold in many others , I suspect , but dar not affirm . Hence it may be ( if mens observations , were frequent in all kind of Anatomical inspections , in several Embryo's of every species ) it would be found evident , that the Blood in all these , called 〈◊〉〈◊〉〈◊〉〈◊〉〈◊〉 hath its immediat original from a simple homogeneous , and uniform liquor , and doth by gradual and frequent influences of the vital ferment of the heart , receive at length the full tincture , essence , and subsistence requisite for vivification , and illumination of the whole members .

Whether this Experiment doth not sufficiently impugn the universality of the hearts first living , the original of the Gall from the fervour , and ebullition of the Blood , the production of the Blood by the Liver , and many other ancient errors , let any judge , who will but take pains to make and compare Harveys trials de ovo , with this of the Porwigl or Gyrinus , ab ovo .

Yea , if the aqueous liquor , be not one with the vital Spirit , and subsequent Blood , then my eyes , and taste are altogether erroneous .

Moreover , it were to be wished , that Physitians would not simply stand upon the Galenick suppositions of the four alledged Components of the Blood , nor any such , or equivalent fancies of the latter Chymists ; but that they would seriously examine the first original , and rise thereof from the Primigenial juice , or liquamen , the progress , and perfection of its tinctures , how many renovations , or new tinctures it is capable of ; the vast difference between the Blood of old and young Animals , ( though , it may be , they are both univocal substances , while in their integrity within the Vessels ) with the specifick discriminations , not only of that of any one Aquatick , from any Volatil , or Terrestrial , but likewise of any one Species living in the same Element , with these that enjoy the same Aliments , but of a different Species . And lastly , the variety of particular constitutions , and singular properties of individual Animals , radicated in the fountain of life , or first original of the Blood . If these things , and many more , were truly inquired after ( though the Cook be sometimes necessitated to throw away some of the Broth with the Scum ) I doubt not but the Neoterick Invention of Transfusion of Blood , would prove altogether ridiculous , and the ancient mistake of too much Profusion of this treasure by Phlebotomy , might suffer some reasonable checks from infallible Experience , and sound reasons , not here to be mentioned . There are truths in Natural Philosophy , which ( I doubt not ) but sound reason and experience will convince the vain world of in due time .

OBSERVATION XXIII .

THis Observation is concerning the aliment and growth of Plants . The inquisitive wits of this , and the last age , having rejected the old opinion of the earths nourishing of Plants , or being converted into their aliment , have made many laudable Experiments for finding out the materials , and means of their growth , and vegetation , such as Sir Francis Bacon's Observe of Germination , Helmonts of a Willow , and the Noble Mr. Boyl's of a Gourd , &c. For though a Tree be cut down , and the root thereof wax old in the earth , and the stock die in the ground , yet through the sent of Water , it will bud , as Iob speaketh , Chap. 14.7 , 8 , 9. I shall add a short remark of a Willow growing without earth . Upon the 13 of April 1662 , I set a top branch of the Peach-leaf'd Willow in a Glass-viol , among 12 ounces of pure Spring Water , with three small buds upon the top thereof , scarce yet discernable . The first ten or twelve dayes , little white specks appeared upon the sides of the Willow , like small drops of Quick-silver , or like the first Bubbles that arise upon the fermentation of Ale or Wine , but no consumption of the Water all this time . Indeed the Gemms , which stood three inches above the Water , did visibly swell about the twelfth day . About the fifteenth day , I perceived small white roots within the Water , upon several places of the Plant , and observed the Liquor grow somewhat thick , and decay in bulk considerably . Having perceived this , I took another Glass of the same bigness , with that wherein the Willow grew , and having filled both top-full with Spring Water , I observed clearly the consumption of the Water wherein the Plant stood , to be so great , that during May , Iune , and a great part of Iuly , every week ( at least ) an ounce and an half , or two ounces of it were insensibly spent : whereas the other Water , standing by in an open Vessel of the same size , made not waste of one spoonful in a whole moneth . About the middle of August , the Water turned very thick , and green , like that whereon Duck-weed useth to grow , and the fair white roots were all obscured from the sight , although the Vessel by the multitude of roots was not capable of the third part of Water it received at first . At this time the branches were advanced to half the bigness , and a much greater length , than the whole stock , at its first planting ; and the leaves of as fresh a verdure , as any Willow in the fields . Thus , having observed , that a tree of four ounces weight , could in three moneths time , and little more , consume insensibly , seven or eight times its own weight of pure Water , without the warm preservation of the earth , and by its own proper digestion , to thicken the remnant of the Water , that it might serve for lorication of the tender fibres of the roots , I took the Glass , the Tree , and all , and threw them over a Window , supposing it needless to recruit the Water any more , and judging it impossible without the warm guard of the earth , that the naked Tree could be preserved in Winter : yet it had the good fortune to fall among some thick Herbs in the corner of a little Garden , where ( after it had lien all Winter ) it was found , and brought back to me , the branches fairly budding in April , the whole Tree fresh and green , yet very little Water was left in the Glass , by reason , as I judged , it had fallen upon its side . Then I endeavoured to keep Water about it , but the Stock filling the neck of the Viol , and the Roots the whole body thereof , the starved Plant died in May , after it had lived a whole year without earth . From this it would seem , that this kind of Tree , ( and it may be , many moe ) doth dissipat insensibly six times more Liquor , than it doth assimilat , and by consequence , that a great quantity of moisture is necessary for maintainance of great Woods . Neither is there any way so advantagious for draining moist ground , where there are no living Springs , as that of planting abundance of Timber , which will best agree with that kind of soyl : for by this means , what was formerly noisome , and superfluous , is now converted partly into the useful aliment of the Timber , and partly sent abroad in insensible exhalations , which ( according to the nature of the emitting Plants ) prove either very noisome , or wholsome to the Neighbour-Inhabitants . Great care therefore would be had in the choise of such Trees , as are to be planted in such moist ground , as are near to mens dwellings , or places of concurse . They are not fools , who prefer Firs , and Lime-trees in their Avenues to Oak and Elme . Let the effects of the Atomical exhalations of Alder and Oak upon fine Linnen , and white Skins be more particularly noticed .

Having spoken somewhat of the aliment and growth of Plants , I shall in the next place give a short hint at the motion of their aliment , especially of Trees . That the alimentary juice of Plants , is much thinner , than that of Animals , no man , I suppose , will deny , seing that is conveyed thorow the trunck , or body of the Plants , by inperceptible pores ; but this ( for the most part ) is sent thorow all the members , through patent and manifest Vessels . But how the nourishing , and vital juice in Plants doth move , and by what passages , hath not yet been made known , by any that I have seen . I made once a few Observations , for trying of the motion of the aliment of Trees , which bred in me this conjecture . The nutritive juice of Trees is transmitted both to the roots and branches , through the heart , or pitch , and woody pores of the Timber , and when it is come to the extream parts , it returns again from the tops of the roots and branches , between the bark and timber , into these forenamed interior passages , and so back to the extremities again , and that continually , so long as the life remains . And because the substance of that skin , or bark , which invests the fibres of the root , is more open and porous , than that which is upon the outward branches : therefore it seems , that so much as is superadded to the stock of the former aliment , from the earth , is conveyed to the heart and pitch , by means of , and together with , that part of the retrograd juice , which returns from nourishing , and enlivening the timber of the root-branches , ( for it is an easie Experiment , to make the top of any Tree become root , by laying it down ) and receives the impressions of the life of the Tree , common to the whole mass of alimentary juice , like the I hyll in Animals mixed with the blood of the Veni-cave , before it come to the heart .

This motion is not to be thought alwayes alike swift , or of equal celerity : for the vital juice of the Tree becomes so thick and oleagenous in the Winter , that the motion thereof to the outward , is scarce discernable ( though the preparation of the Gemmes , both for leaves and flowers , are observed by the curious , and can be distinguished , even in the coldest seasons ) and the returns inward are in so small quantities , that they are rather like vapours , than liquid juice . Indeed , some Trees , when their root-branches are cut ( even in Winter ) will yeeld no small quantity of an acid liquor , which by addition of the recent Leffas from the earth , smells evidently of the Matrix , from which it did proceed . Moreover , the passages especially from the branches to the Trunk , are so straitned and contracted , that the bark cleaveth to the Timber , as every Wood-man knows . But so soon as the warm Spring hath attenuated the ever-flowing juice in the whole Tree , then doth it become turgid , and more aqueous over all : the passages , and channels both in the trunk , and among the tunicles , and particular skinnes , are so palpably filled with this vital juice , that having no sufficient place to be comprehended in , it putteth forth new growths both in the top , and in the root , which may be easily seen to have more pitch than wood , and to be sealed on the extremity , with the vestiges of a future Gemm ; that by the former , they may the more freely receive the vital influences from within , and by the latter , may be secured from the depredation of the external Air.

To prove the motion ad extra , or to the extremities of the branches ; take the branch of any ordinary Tree , about the bigness of a mans wrist ; make it bare near the body of the Tree of all bark , and subjacent tunicles ( for every Tree according to its kind , hath moe or fewer skins , which serve for Veins , within the strong outmost Cortex ) at least for the breadth of a span , or two hand-breadth . Then tye up the place , so excorticated with a compost , made of horse-dung mixed with earth ; let it stand so from May , till November . Then cut off the branch , a little above the Compost , near the body of the Tree , and you shall find it living and fresh , like the rest of the branches : yea , small roots shall evidently appear to have come forth under the Compost near the bark , but not under the bared place . This branch in many kind of Trees being planted , will hold , though not in all . I say then , seing the foresaid bough is nourished from May till November , it is necessary , that it receive nutriment from the body of the Tree , by the internal porosities thereof : for the bark being discontinued by excortication , can send nothing upward towards the top of the bough ; and if it received nothing from the root , it would wither in a few dayes . Yea , leave the discovered part naked , but for a few dayes , and of necessity the branch dieth , the aliment thereof being exhausted by the Air , before it can reach the extremities of the bough .

That the Vital Balsome of the Tree returns from the extremities by the internal bark , and inward superfice of the external , together with the smooth outward part of the trunck , although the necessity of both timber and bark in all Incisions , and Inoculations , might perswade the judicious , and the visible course of the juice of the Sycamor in February , and of the Birch in March , upon the cutting of any small branch , might convince any curious beholder ; yet the knot or callus , that is made upon grafted Trees , will better inform the ignorant : for this knot being alwayes upon the shoulder , or root of the Graff , and never upon the top of the Stock , doth evince clearly , that it is made by restagnation , of the descending , and not of the ascending juice : otherwise , why doth it not swell the top of the Stock , as well as the root of the Graff ? Or why doth it not extuberat in any other place of the Graff ? These are accidental varices , which can hardly be shunned in Imping , seing the top of the Stock ( except when it is very young and succulent ) doth not receive so kindly , as it ought , the retrograd sap , although all that is sent out to the Graff must ascend thorow the pores of the Stock . Hence many times a considerable part of the Stock is mortified , because although abundance of aliment ascends to the head or top thereof , yet no more of it goes to the branches , but what is bestowed upon the Graff , a great part of the rest being exhaled by the Air ( especially in big Stocks ) and consequently , the place defrauded of its nourishment : no other wayes than when the motion of the vital sap faileth , either in the whole , or in part , a total decay or particular mortification of some part necessarily follows , as in the Stemms of annual Plants , and mortified tops of the Ectrapelous branches ( that I may so call them ) of Willows , Plumbs , &c. we may observe every Autumn .

OBSERVATION XXIV . Sir ,

I Was not a little surprised , at the receit of yours , when I had considered your desire in it , being prest with two difficulties , which seemed equally hard to evite . The one , to give you my judgement in a matter wherein I have been so little conversant my self , and have had the steps of no other to follow , never one having hitherto touched that subject in writting ; I mean of Coals , and other Minerals of that nature , their Course , and other things relating thereunto ; the observation whereof ( I grant ) wants not its own pleasure , and usefulness . The other , to refuse the desire of a friend , when importuned , to whom I owe my self , by many obligations . This last having prevailed , hath determined me to assay the overcoming of the first . And though I am confident , what account I can give you , shall give but very little satisfaction : yet I adventure to offer it , such as it is , very freely in the following discourse , wherein you are not to expect , that I will meddle with some questions , thereanent , which might be more curious , and pleasant , then profitable , or satisfying , such as , if Coal , and Free-stone , which keep one course , and have the same accidental qualities , have been created in the beginning , in their perfection , as wee now find them , and since that time only preserved , as they were created for the use of men , to whom all sublunary things were made subservient ? Or , if they have been but produced gradually , as they speak of Gold , and other Minerals , by the influence of the Sun , in the bowels of the Earth ? And if their production be of that nature , out of what matter they are formed ? These things being above my reach , I shall leave their inquiry , to those that are knowing in the secrets of Nature , and shall therefore give you a narration , of what either I have observed of these things , which occurr in the Winning of Coal in my own experience , or by conversing with others of more experience than my self , in doing whereof , I shall follow this Method .

First , I shall speak of these things that are common to all Coal , wherein they all agree , and which are , as it were , essential to all , and of there differences , which are but accidental , and gradual sometimes , and yet are abundantly conspicuous , and causeth different effects in the working ; as their Dipps and Rise , and Streek , for so are they termed .

Secondly , of some things , which are but accidental to Coal , and yet so ordinary , that scarcely any is found without them , in lesser or greater degrees ; such are Gae's , and Dykes , that alter the natural Course of the Metalls , very incident to every Coal , though in some less frequent , conform to the nature and kind of the ground , where the Coal is .

Thirdly , I shall speak something of Damps , and of their different causes , and effects : of Wild-fire , and other such like things , which are met with in the working of Coal .

And lastly , of the best way for trying grounds to find Coal , where never any hath been hitherto discovered : of carrying on of Levels , for draining the water of Coal and making it workable .

It is to be cosidered , that all Free-stone , though of different natures , hath the same course , with the Coal , that ly either above them , or below them , except it be accidentally , interrupted : therefore , whatsoever is spoken of the one , is applicable to the other . And so we find in Digging or Sinking , that after the Clay is past , which keeps no course , all Metals , as Stone , and Tilles ( which are Seems of black Stone , and participat much of the nature of Coal ) ly one above another , and keep a regular Course ; wherein the three things most remarkable are their Dipp , and Rise , and their Streek , as it is termed .

The Dipp , and Rise , are nothing but a declining of the whole body of the Metalls . And this general holds , that all of them from their Center rises , till they be at the very surface of the Earth ; some only at a foot or two foot , some at an ells distance from the surface , which is here termed a Cropping : and whether Coal or Stone , the nearer they come to the surface , the softer they become , till at last they are converted , if it be a Stone , to a very Sand , and if Coal , to a Dross , which will not burn .

This declining or Dipping , of the Coal , is sometimes greater , and sensible , sometimes lesser , and almost insensible . There being some , that if you consider the declination , it will not be found one foot in ten ; some one foot in twenty , or one in thirty . Whereas in others it will be one foot in three , or one in five . And sometimes it hath its Course from the Center of the Earth , almost in a perpendicular to the surface , it cutting it , near to a right Angle . The first sort , they term Flate-broad-coal , in regard of the plainness , and evenness of its Course . The next , they call Hinging-coal . The last is called Edge-Coal . The first is the most profitable , in regard , that it 's long before the Coal-hewers can reach the Cropp , and consequently the more of it is workable . The second and third sort , are sometimes of their own nature , more firm , and fitter for burning , but less of them can be reached in working . The Course of all the three is most perceptible in the three following Schematisms .

Figure 1.

In all the three Figures , the point B is the Cropp of the Coal . The Line BC is the body of the Coal declining or the Dipp from the Cropp . AC is the perpendicular , falling from the Horizontal Line , whereby the true declination or Dipp of the Coal is found . So that after you have found your Coal at B , you must set down your Sink at the point A. In the Flat-broad-Coal , which we suppose only to decline , three fathoms in sixty ; the Sink , that answers to the perpendicular AC , will be of deepness three fathoms . If the distance BA , be supposed to be 120 fathoms alongst the Grass , or surface , then will the deepness of the Sink be six fathom , and so forth . In the second , if the Coal be supposed to decline one fathom in three , the Sink AC , being set down at the same distance from the Cropp B , with the former , it will prove thirty fathom deep . If the said distance be doubled , it becomes sixty fathom deep , and so forth . In the third , keeping that same distance alongst the surface , you shall not encounter the Coal with a Perpendicular Sink , because of its great declination , and therefore through want of Air , and other difficulties , you cannot dig so deep , as is necessary to that effect , except the Sink should be made to decline , as doth the Line AD. All these Dipps are to be seen in several places of Lothian . The first is most conspicuous in the Earl of Wintons ground at Tranent , where the Coal , and other Metals are extraordinary flat and even . The second is within the said Lordship of Tranent , in a piece of ground , called Wester-Fauside . The third in Lonhead of Laswaid , which pertains to Sir Iohn Nicolson of Nicolson : and in many other places , one may see very different declinations , who is curious to observe them .

From this general position of the Dipp , and Cropp of all free Metals , there is one consequent , which is no uncouth Observation , namely that these Metals rising from their Dipp to a Cropp , every one of them riseth in their proper course , if none of these things whereof we shall treat hereafter interveen , and make an alteration , that is the Coal or Stone , which is lowest , comes farrest out in its Cropp●ng , which is easily understood by the subsequent Schematism .

Figure 4.

Wherein the Line AM represents the surface of the Earth . CD . EF. GH . IK . LM , are so many several Metals , lying in course one above another . Suppose CD were a Stone , and the Roof of the Coal EF ( for so they term the Stone , immediatly next above the Coal ) and GH , IK , were other two Stones , interveening between the Coals EF , and LM , then if the Cropp of the uppermost Coal be found at F , the Crop of the Stone above it , must be found back , at the point D , and the Cropp of the Coal under it , which is LM , must be found at M. And this distance of Cropp is proportioned by the length of the perpendicular between them , and the quantity of their declination . For , the more even and flat a Coal is in its course , and other Metals , above and below , the farder doth the Cropp of the lowest Coal advance before the Cropp of the uppermost . For illustration whereof , let us suppose in two several grounds , two Coals , between which , there is an equal distance of perpendicular . And suppose the Metals in the one ground to decline at 13 to 24 , the other at 13 to 16 , then will the distance between the Cropps in the two grounds be very considerable , as may be represented by the two following Figures .

Figure 5.

Suppose then , that DI , is of equal length in both Triangles , which is the perpendicular , between the two Coals : yet DF in the fifth Figure , is much longer than DF in the 6. And the reason is evident , because the Angle DIF , in the 5 , is greater then the Angle DIF in the 6 : and therefore the Base DF , which is subtended by the greater Angle in the 5 , must be greater then the Base DF , which is subtended by the lesser Angle in the 6 , which Euclide proves in his 24. Proposition of his first Book , and is demonstrat by Proclus in the Scholium to the 4th Proposition of the same Book .

By this is made to appear the profitableness of a Flat-Coal , beyond a Hinging-Coal , which was touched before , in regard that having the Sinks of equal deepness in both , there is much more of the Flater-Coal to be wrought , before it Cropp out , then of the Hinging , as there is a difference between the Lines DF in the first and second Figure , or between the Lines IF , in the same .

If it be enquired , if in rising grounds , where there is a considerable ascent above ground , the Coal keeps a proportion in its Rising and Dipping with the ascent and descent of the ground above ? I answer , there is no certain and constant proportion kept , whatever sometimes may happen . For I have observed some Coals upon grounds of a considerable ascent , and their Dipp run quite contrary to the descent of the Hill : and others have had a quite contrary course to that , and have declined , or dipped with the declination of the ground above ▪ But in the Streek ( whereof I shall speak a little hereafter ) there is more proportion ordinarily to be remarked .

There remains only one Question about the Dipps , and Risings of Coals , which I shall a little consider , having encountered different judgements anent it , in conversing with persons , who had experience in Coal , viz. whether Coal and other Metals , after they have declined such a length from their Cropp , suppose from West to East , take another course , and rise to the same point , to which formerly they dipped ?

Figure 7.

As if the Coal dipped from A , which is the Cropp , to B , which should be the Center of that Body ; and after that rise to C ? Or if it should continue its declination thorow B to D , which is Antipodes to us ? I shall not offer to determine in a matter wherein there can be so little certainty attained , but shall give my opinion , which is founded upon the experience I have had , and Observations I have had occasion to make on that Head . And first , I find in all these Coals , wherein no contrary Cropp or Rising could be visible , there are invincible obstructions ; as either , they have been near the Sea , and have dipped that way ; and so if they took any contrary course , the cropping behoved to be in the deeps , and so no access to trace them . Or next , they have dipped towards the foot of a Mountain , and so the ground above rising the same way which they declined ; their course could not be pursued , till a contrary rising should be discerned . Or thirdly , they have encountered some Gae , or Dyke , which hath cut them off , before they came to their full dipp , and thus their course was obstructed . Now , those that have been acquainted with no other Coals but such , I think it not strange , if it be hard to perswade them of those things they have not seen . But besides all those kinds , I have seen others , whose contrary rising and dipping have either been visible to the eye , or demonstrable by reason . For example , I have entered under ground , as it were at the point C , at the very Grass-cropp , and have gone following the dipp of that Coal to the point B , at which the course hath altered , and carried me out at the Grass at A , which are two contrary points of the Compass . And that alteration of course was not occasioned by any Gae , or trouble , which sometimes have that effect , the ground being very clean , and good Metals , keeping their course most regularly .

There are other instances for confirming my experience , in fields , which are so large , that 't is impossible to work the Coal so far to the Dipp , it falling deep , and so wants Level for conveying water from it , or wants Air , for following it to such a deepness , as to overtake its Center , where it takes a contrary course , and yet the contrary Cropp hath been wrought in several places , which is evident to be a part of the same body , with the other , both by the nature of the Coal it self , by the Metals lying above it , and the Coals below it , all which keeping the same Course , except when they encounter troubles , which are incident to some parcels of ground , more than to others . The greatest field I know wherein this is conspicuous , is in Mid-lothian where is to be found , the cropping of a Coal of a considerable thickness , which is termed their great-seam , or Main-coal , and the other Coals lying below it , which may be traced in the order following . At Preston-Grange these Coals are found dipping to the N W , and rising to the SE , which have been wrought up to Wallifoo●d : from that along by the foot of Fauside Hill , the dipp lying in the Lands of Inneresk , which marches therewith on the North. From thence it runs through the ground of Carberry , every one of these grounds from Preston-Grange , Giving Levell to another . From thence , through a part of the Lands of Smeaton , and next through a piece of ground belonging to the Family of Buccleugh , called Condon : and through West-houses , which belongs to the Earl of Lothian , and at Cockpen , and Stobhill , from thence runs through to Carington-Mill ; all which is a course , which in Streek lyes near to SW , and NW , and will be in length about eight miles . From thence , the course of the Coal turns , and is found in the Barony of Carington , White-hill Ramsay , Gilmerton , and from thence taking its Dipp , quite contrary to what it had before , the other Dipping N and NW , or NE , according to the turn of the Streek , it Dipps there S , SE , &c. and from Gilmerton , it is found at Burntstone , a piece of ground belonging to the Earl of Lauderdale : and from thence at the Magdalen Pans , where the turn of the cropp being within the Sea , is not seen , till it be found at Preston-Grange , where we began to remark its course . The parcel of ground , under which this great body of Coal lyes , is of a considerable extent , it being eight miles in length , and five or six in breadth ; in regard whereof many other Coals are found lying above the great Coal , the cropps whereof doth not come near the Cropp of it , by a considerable distance .

Though this instance alone , may sufficiently convince , yet I shall not be unwilling to give another . The parcel of ground , in which this Coal is found , is not of so great an extent , as the other , and therefore its course may be the more easily traced . For the greatest part , it belongs to the Earl of Winton , and lyes within the Lordship of Tranent , whose contrary Cropps , are most conspicuous . This great Coal , which is 10 , or 12 foot thick ( beginning at the head of the Toun of Tranent ) where it hath been wrought , runs SW towards the march of the Lands of Elphingston , belonging to the Lord Register , and continues in that same course , till it come near to the house , and for the most part dipping to the SE. And near the house , the Cropp is turned downward towards the march between Elphingston and Ormiston , where the dipp is contrary to the former . And from Elphingston-mains , it takes its course almost round , through the Lands of Panston , and returns to the Toun of Tranent where it began , which body of Coal will be in length two miles , and in some places , as much in breadth . Now , I leave it to the judgement of any person , if there be not more reason to perswade , that this should be the natural course of these Minerals , where such pregnable instances , to evince it , are found ; then to conclude the contrary from these Coals , the course whereof cannot be followed , because of the invincible impediments , I mentioned before . However , I leave every one to be determined , by his own opinion , and shall be satisfied to injoy my own , till these of more experience convince me of the contrary .

There are some other things farder to be remarked about the Dipp , and Rise of Coals , which ( possibly ) every one hath not seen , they being so very rare , and therefore are not fit here to be passed without being considered . One is , of a Coal , which having that contrary Dipp and Rise , ( whereof I have been speaking ) in one of the cropps , hath not come out to the Grass , and terminat ; but after it hath risen a considerable way in its contrary course , in stead of Cropping out , hath taken a Dipp towards the same point , to which it dipped first , and so having dipped to the Center of its course , it hath risen again , and cropped to the contrary point , as is to be seen in this eight Figure .

Figure 8.

Where AB is the surface of the Earth . The point B is the Cropp of a Coal dipping from NW , to the SE. From C it takes its rise , and course to a contrary Cropp , towards the point F , where the dead Cropp ought to be found . But in stead of going that length , it takes another course from the point E , dipping SE towards D , from which it takes its rise , and continues it to the point A , where it terminats , and where the dead Cropp is found . I grant , that it meets with a trouble , or Gae , at the point E , which seems to be the cause , why its natural course is changed . But it s very extraordinary to see such an effect . But of this afterwards , in its own place .

There is yet another thing to be remarked , in the dipps , and risings of Coals , which is this . In the most part of Coals , that have their course from dipp to cropp , without the intervention of a dyke or gae , the declination is straight down , from the horizontal line drawn from the point of the cropp , to the fardest point of the dipp . That is , the Coal declining from that point in a right line , makes with the horizontal line , a right lined angle , angulus rectilineus , though in some the angle is more acute , and in others less , as is to be seen in the first , and second figures , where AB being the horizontal Line , and B the cropp , BC is the body of the Coal declining , which meeting with AB in the point B , constitutes a right lined angle , and where ABC in the second figure , is a greater angle , then ABC in the first . Yet I have seen a Coal , the body whereof from the dipp , or fardest point of declination , had its rise towards the cropp very insensibly , it being Flatt , and then began to be more sensible , till at last coming near to the surface of the Earth , it takes in a sudden such a rise , that from declining one foot of 12 or 14 , it declines now one foot of three , as may be made evident from this following Figure .

Figure 9.

Where AB is the Line drawn from the extream points of the Cropp , right horizontal . The body of the Coal rising insensibly , is DC . But assoon as it comes to C , it riseth with a great ascent till it Cropp out at A. Here you see , that in stead of one side of a Triangle , which the course of other Coals in their rising , or in their declination makes ; this Coal in rising makes two sides , namely DC , and CA , the Figure DBCA being quadrilateral . The Coal of this course was really wrought , and is yet visible in its waste , where there is found no Gae or Dyke to make this alteration .

These are the chief things that I have thought worthy of Observation in the Dipps , and Risings of Coals , and therefore I come now to touch a little the other part of their course , which is commonly termed the Streek of a Coal . To make intelligible to those , who are not experimentally , acquainted with Coal , this term , or what the Streek is , we must lay this foundation , that the Coal is a Physical Body , and so hath its three principal dimensions , which do constitute it so , viz , Longitude , Latitude , and Profundity . It s Latitude , is that part contained between its extream lines , which is measurable by its surface , to which its dipping and rising , though alwayes incident , yet is but accidental . It s Profundity is to be measured by the distance , between the two surfaces , immediatly next to it , above and below : which are termed in Coallery its Roof and Pavement , because of the resemblance they have to the Roof , and Pavement of a house . The Longitude is nothing else but what is termed by the Coal-hewers , the Streek . For if you imagine a Line drawn along the extream points of the Rise , or Cropp of the Coal , that is properly the Streek of the Coal .

There are but few things to be remarked , as to this part of Coal : only first to find how it lyes , to what points of the Compass it moves . For knowing whereof , there is this general Rule , that , having found your Dipp and Rise , to what ever Points that Course is directed , the Streek is to the quite contrary . For supposing a Coal Dipp SE , the two points , that respect the Dipp and Rise , must be SE , and NW , being the points opposite one to another . Then it must needs follow , that the Streek must run SW , and NE , which two courses divides the Compass , at right Angles . And therefore , where a Coal is found to have contrary Dipps , and Risings , they declining sometimes to all the Points of the Compass ( whereof there hath been given two notable instances before ) it must needs follow , that there be also contrary Streeks , and so the Streek of a Body of Coal is sometimes found to describe a round figure , though not perfectly circular , and somtimes a multangular figure . For it cannot be supposed that the Streek makes alwayes a right Line , between the two points , from which it is reckoned . For example , between the Laird of Preston-grange his house at Preston-pans , and the Stob-hill , there are the Streeks of several Coals , lying one above another , which will be of length , about seven or eight miles , lying near upon SW , and NE ; yet the Cropps of the said Coals ( their dipp , and rise , being NW , and SE ) are sometimes farder advanced towards the SE , sometimes farder back towards the NW , by the difference of a mile , and this generally occasioned by the encounter of a Dyke or Gae , whereof hereafter .

The same question , that occured in the Coals dipping towards a Hill , on rising above ground , comes to be inquired into here ; viz. If a Coal encountering amascent , or Brae above ground in its Streek , rises also with the ground , and keeps its ascent ? I answer , I have found it so in all the Coals I have ever seen of that nature . GOD in his providence , having so ordered it , that thereby it may be the more useful , in regard more thereof may be wrought by one Level or Aquaeduct , by which the Water is conveyed away , as afterwards will be observed in speaking to Levels . For confirmation whereof , I shall bring instances both of Coals , that declines towards the Hill , and of others that declines with the same dipp , the Hill hath it self . In the Coals of Bonhard , Grange , Kinglassy , and Kinneil , which keep all one general course ; the ascent above ground is from the Sea , ( which lyes North ) towards the South , or thereabout ; the Coal dipps or declines towards the NW , and so consequently rises to the SE. The Streek of these Coals , is from the NE to SW , which slops alongs the Hill , and comes up to the top thereof to the Westward of the House of Bonhard . Now , in sinking in that ground , if an equal proportion be kept , in all the Sinks from the Cropp , and a just allowance given for the different Rising above ground , the Sinks will be near of an equal deepness along all the Streek . So that a Sink upon the same Coal near to the Sea , which is the NE point of the Streek , at equal distance from the Cropp , will be as deep as a Sink upon the top of the Hill , being the SW point of the Streek at the same distance from the Cropp , allowing alwayes the different rise above ground , and excepting some particular troubles falling in upon the Metals of one Sink , and not of another , and so making them dipp more , which will occasion a difference of the deepness . The same is also found in the Coals of Dysart , and Weems . As also in that great body of Coal before mentioned , between Preston-grange and Stobhill , the declination whereof is to the NE , which is also the course of the descent above ground .

Another instance is from the Coals within the Lordship of Tranent , the dipp whereof is of another course , being contrary to the descent of the Hill , viz. the Coal dipping to the SE , and consequently the Streek running SW , and NE , where the same is to be observed that was seen in the other , anent the equality of the deepness of Sinks along the Streek , with the same allowances , and exceptions before mentioned .

Some have been of opinion that Streeks of Coals ly generally South and North , or to some of the points near to these two Cardinal ones , between South and SW , and North and NE , as South and by West , and North and by East , &c. To which general I cannot agree , in regard of wh●● I have before made evidently appear , viz. that some Coals have their croppings towards all the points of the Compass , and the Streeks being regulated by the Cropps , they must necessarily be judged to have their courses proportioned to theirs : so that if a Coal dipp to the true North , and rise to the South , the Streek must be East , and West . However , I acknowledge two things , for confirming that opinion .

First , that of all the Coals I ever have seen , where these contrary dipps and risings , could not be traced , and made visible , the Streek hath inclined to those points of South and North. But I must also confess , that they are but few I have seen , in respect of what I have not seen , and so if any others experience , who have seen more , contradict mine , I shall willingly yeeld , and not be tenacious .

Next , in these Coals , which I instanced , that have their Cropp to all the Points , and consequently their Streeks , and in others of the same nature , which I have seen , and not instanced , I found that part of the Streek , which lyes towards these Cardinal points , to be the greatest , being double , or triple to the other Sreeks in length . So that when the Streek , that lyes either along the one Cropp , or the other , towards the SW , and NE , will be seven miles in length , that lying SE , and NW , will be but four , and sometimes less . And this is all the account I can give , of that part of Coal , called the Streek .

The second thing I promised to speak of , was of some things , which are but accidental to Coals , and yet so ordinary , that hardly are any found without them in lesser , or greater degree , such are Gae's , and Dykes , which alters their natural course , and they being the occasion of so much Trouble , in the working of Coal , and following its course , the Coal-hewers call them ordinarily by that name Trouble . This Trouble or Gae then , is a Body of Metal falling in upon the course of the Coal , or Free-stone , obstructing , or altering their kindly and natural course , keeping no regular course it self , and being of nature alwayes different from the Metal , whose course it interrupts . And these Gae's differ also among themselves , in their nature , and in their course they keep : or more properly in the way wherein they encounter other Metalls , and in their effects . In their nature , for some of them consists of an impregnable Whin-Rock , or Flinty-Stone , thorow which it is almost impossible to work : and if there be a necessity to cut them thorow , it is done at a vast expence , and takes a long time , and must be cut open to the surface of the earth , it being impossible to Mine it under ground . Some of them are again of Stone , like a Free-stone , but seems rather an abortive of nature , they having no rule in their course , by which a man can follow them , nor can their stone be useful .

In their encountering of Coals , or Free-stone , sometimes they encounter them in the Dip , and sometimes in the Streek , and sometimes between the two . These that are met with in following the Dipp of the Coal , ly along the Streek thereof . For example , if the Coal Dipp SE , the Gae lies NE , and SW . These that are encountered in the Streek , lyes to the Dipp and Rise : so the Coal Streeking NE , and SW , the Gae is found to ly SE , and NW . Others of them , lyes between Streek and Dipp , that is to some point between the two : as the Streek being SW , and NE , and the Dipp and Rise SE , and NW , there may be a Gae found lying WSW , and ENE . Now , when I speak of a Gae's lying to such Points of the Compass , this doth not contradict what was said before , that they had no regular course themselves . My meaning being , that though they have a certain length , lying between two points , and a thickness between two Metalls , yet by the Metal of the Gae it self , it is impossible to know its course , as it is in other Metalls of Coal or Free-stone , whose courses are discernable at the first view .

Their effects are different , as their nature and course are different : only they agree in these two generals . First , that all of them renders that part of the Coal , that comes nearest to them , unprofitable and useless , though some less , and some more , they being unfit for burning . And it is remarked , that these Gaes that consists of Whin-rock , renders the Coal next to it , as if it were already burnt , being so dried , that it moulders in handling it . In others , the Coal is not altogether so ill , and yet its nature is altered , from what it is at a distance from the Gae . The next general is , that all of them alters the natural course of the Coal in less or more , some of them making it Dipp much more then its ordinary course , which they call Down-gaes : Some again making their rise much more than their course , which they call Up-gaes . Others making an alteration as to the Streek , causing it go out beyond its ordinary bounds , as we observed before in that great Streek of Coal between Preston-Grange and Stobhill .

Now it is to be considered , that when in working of a Coal , whether to the Dipp , or Rise , or Streek , one of these Gaes is encountered with , the Coal is quite cut off , and as it were terminat : so that you see nothing where the Coal should be , but either a Stone , or Clay , or rotten Till , or some such thing . And the practique of Coallery is to trace the course of the Coal through that , till you overtake it in the other side . And before any thing be said to that part , you must notice , that some Gaes are of greater force than others , and their influence upon the course of other Metalls greater , whence you shall see a threefold effect . One is , that by some great Gaes , which a Coal meets with , it is quite cut off , so that in the other side thereof , there is not a vestige of that Coal , or of any other Metal that was above it , or below it , to be seen . And if there be any other Coal , as sometimes there are , they are quite different from them of the other side . I said by some , because there is one instance to the contrary , which is somewhat singular . In the Earl of Winton's ground at Cockeny , there is found a course of Coals and Free-stone , dipping to the SE in the Links ; and upon the full-sea-mark , there is a tract or course of Whin●rocks lying E and W , underneath which these Coals and Stones comes thorow without alteration of course , and are found within the Sea-mark , with the same Dipp and Rise upon the North side , they had upon the South side of the said Rocks : and yet the Coal is encountered upon the South hand by a Gae under ground , through which it passeth , not without a considerable alteration .

The greatest of these Gaes , that I know , is that which takes its beginning , that we see on Land , at the Harbour of the Pans , called Achisons-Haven , which hath been cut by Preston-Grange , for Level to his Coal , and goes from that to Seton , which may be traced above ground , almost the whole way ; and hath been cut at Seton●a ▪ for serving the Level of that Coal now wrought at Tr●nent . From thence it passeth through the fields of Long-Niddry , a place pertaining to the Earl of Winton , and through the Coats , which pertains to the Earl of Hadington , till it joyn with Pancreck-hills , a tract of Rocky-Mountains , from whence it is traceable to Linton-bridges , where it is v●sible in the Water , the Water of Tyn falling over it , and making a Lin , which they call Linton-Lin ; from thence to the East-sea . And it is known by Sea-men , that it keeps a course thorow the Firth from Achisons-haven , ( whence we reckoned its beginning upon Land ) towards the West and NW , it being found to the Southward of Inch-keith , and before Leith , where stands a Beacon , and so can be traced to the North Shore .

The second effect of Gaes , is to cut off the Coal quite , as to a part of the field , so that in the other side , having pierced the Gae , you shall not find the Coal , and possibly not within a quarter of a mile of the Gae , which cuts it off , and at that place shall only find the Cropp and the Body Dipping , as it did before it was cut off ; and if you shall measure between that side of the Gae , where you lost your Coal ( I suppose the Coal then being 24 fathom from the Grass ) to the place where the Coal in the other side of the Gae shall be found at the same deepness , it will be near 500 paces . For making this more intelligible , let us suppose a Coal Dipping SE , and in working to the Dipp , there is a Gae encountered with ( This was really done in a piece of ground I know , and so it is no meer supposition ) at which Gae the Coal is cut off ; for finding whereof the Gae is pierced , and nothing found in the other side , viz. in the SE side of the Gae , but at more than 100 paces distant , the Crop of a Coal , which lyes under the Coal , that was lost , was found , after which it was easie to find the other . Now , that it was the same Coal , that was lost , upon the North side of the Gae , is not only evident , by the kind of Coal , and all the Metals above , and below keeping the same course , but by this , that the Gae wearing out towards the West , the two parts of the Coal that was separated by it , joynes themselves again , and continues in one body , as they were before separation .

The last effect of the Gae is , that it doth not quite cut off the Coal from the other side of it , but makes an alteration in the course , either in the Dipp , or in the Rise , or Streek , as was before noted : so that in meeting with one of these Gaes , having considered its nature , and pierced it , the Coal will be found in the other side , immediatly touching the Gae , but with an alteration of course . Now , in these two last effects , since the Coal is not totally cut off , it will be worth the inquiry , to find the surest way of recovering the Coal after it is lost . Therefore , where the Coal is not cut off , by a considerable distance , and having pierced the Gae , it is not to be found in the other side , you are to consider well the nature of the Metals you find approach to the Gae , and if they be such , whether Stone , or Coal , as you know to ly under the Coal that you have lost , then you may be sure the Coal is to be found above in its course , which is to be traced by the Dipp of the Metals you find . As sometimes I have seen , when a Coal hath been cut off by a Gae , happly there is another Coal under it 12 fathom , after the Gae hath been pierced , and the lost Coal not coming near to it in the other side , that hath been found there , by which it was certainly concluded , that the uppermost Coal behoved to be there also , though a little back , conform to its course . But , if the Metals or Coals , under the lost Coal , hath not been known , then you are to take notice of the Dipp and Rise of these Metals , you find on the other side of the Gae , which you have pierced , and making that your rule , range back over the Metals , conform to the direction to be given afterwards , and you shall find the Cropp of the Coal you want , and after which you were inquiring .

Where the Coal is not quite cut off by the Gae , but hath its course only altered , you are to consider , in searching for it , before you pierce your Gae , that which the Coal-hewers term the Vise , or some of them the Weyse of the Gae , which in effect is nothing else , but a dark vestige of the Dipp or Rise , that the body which now constitutes the Gae , should have had naturally , if it had been perfected ; which when it tends downward , then must the Gae be put over that way , and in the other side shall the Coal be found , and Down , as they term it ; that is , the Dipp which it had naturally , augmented . And , if the Vise be Up , the same way must be taken for piercing the Gae , and the Coal will be found Up , that is , its Rise augmented . But these things cannot be made so intelligible , as by seeing , there being many things in the alteration of the course of Metals very curious , and worthy of Observation : as when a Coal is cast down out of its natural course by a Gae , and so made sometimes under-Level , it riseth as much to another hand , and the Cropps go so much farder out , which still makes the Level useful , the use whereof would have been judged lost by the down-casting . Sometimes a Coal made to have four contrary courses , as is evident from the eighth Figure , where there being a Gae at E , makes it take such another course , in stead of coming out to the grass . Sometimes , before the Metals overtake the Gae , they are made to ly like a Bowe ; one instance whereof is visible above ground in some Metals lying between Bruntiland and Kinghorn , at a place called the Miln-stone , where there is a small Coal with Free-stone above it , all Dipping to the S E , and Rising to the N W. Upon the Rise they meet with a gae , which is a great Whin-rock . In their course to the grass , before they touch the said Rock , they take a contrary course , and dipps into it , and are there quite cut off . The manner whereof is to be seen in this tenth Figure following .

Figure 10.

Where AB is the Rock : EF the Coal : CD the Free-stone . Now , whereas they should have risen towards A , they turn at D , and dipps into the Rock , which any may observe in passing that way . Many other such motions are observable , which I pass , and leaves them to the observation of the curious .

The third thing I promised to speak of , was of Damps , and as they are termed by the Coal-hewers , Ill Air. These do deserve a more accurat inquiry into their kinds , their causes , and effects ; then I am capable to make , there being many things in them very con●iderable , and worthy of a narrow search : therefore following the course I have hither to observed , I shall shew my own Observations thereof , and leave the more curious search to the spirits fitted for that purpose .

This Damp then makes an obstruction of respiration in Men , or other living Creatures , in Subterraneous spaces , as Caves , Coal-rooms , Levels , Sinks , and such like ; which obstruction proceeds principally from two causes , both which goes under the name of Ill Air , among the vulgar . The first is the corruption , or putrefaction of the Air , whereof there are two sorts ; one is in places where hath been fire kindled , which burns the Coal under ground , the smoke whereof , being full of Sulphur , and other Bituminous matter , and not having free passage to come above ground , filleth all the waste Rooms under ground , and infects the Air so , that the smell of it , even at a distance , is intolerable , and amongst it no living Creature is able to breath . Of this there are examples in Dysert in Fife , and Fauside in East-Lothian . This was kindled on design by a Fellow , who for his pains was hanged in the place , and hath burnt these 50 years , and more , the fire whereof is sometimes seen near the grass , with abundance of smoke , as it runs from one place to another . The second , where the Air is corrupted without the mixture of smoke , or any other gross corrupting body , which is the most considerable of all Damps , and hath the strangest effects , in killing Animals in an instant , and so hath been alwayes most prejudicial in the works , where it is found , many persons having thereby lost their lives , without access to cry but once Gods mercy , to some instances whereof I have been witness . I shall not offer to determine about the cause of this Damp , but shall give an account of somethings I have observed about it , which when duely pondered , may haply lay a foundation , at least of a probable conjecture , whence it may proceed .

This kind of Damp then , and Ill Air , is never found in Coal , or other Metals , where there is Water to be found ; I mean , whence the Water hath not been drawn away by a Level , or Aquae-duct : as in Coals , where there is a necessity to lave the Water from place to place , or to pump it along the ascent or rise of the Coal , to the bottom of the Sink , from which it is drawn out above ground , this Ill Air is not found . Nor is found frequently , if at all , in these Coals where the Water is drawn from the Coal by a Level , or Aquae-duct under ground , till it come of its own accord to the bottom of a Sink , which is in place of a Cistern , out of which it is forced also above ground , and differs only from the other , that the Water runs here of its own accord by a descent to the Sink , which is termed a drawing Sink : in the other it must be forced by the Rise of the Coal , because happly , a Sink upon the Dipp would be of such a deepness , that no force could draw it up in a perpendicular .

But this kind of Damp is found ordinarily in these Coals from which the Water is drawn by a Level , the beginning or mouth whereof is above ground , and carried along by a right Line under ground , till it overtake the Coal , which it is to d●y : so that the Water which comes from the Coal , runs without being forced , and is sometimes so considerable , that it makes Mills go , without any other addition , as is to be seen in the Earl of Wintons Lands of Seton , where four Mills goes with the Water that comes from under ground , out of the Coal ; which kind of Levels are only found where the Coal lyes in a Field , which hath a considerable Rise , or ascent above ground ; there being a necessity to make use of the other two wayes spoken of , for drying the Coal , when the Field in which it lyes is a Plain .

Further , of these Coals , which are dryed by the Free-level ( for so they term the Level that runs unforced ) there are some to which this kind of Damp is more incident , than to others . The cause of which difference is found to be , the solidity and clossness of the Metals , whether of Coal or Stone , wherein some exceeds another . There being some , that are full of rifts , or empty spaces ( I mean empty of any part of the same body where they are ) which will sometimes serve , to convey a considerable quantity of Water in place of an aquae-duct or level ▪ which spaces are termed by the vulgar , Cutters , which sometimes proves very profitable in the ground where they are found , both in regard of the use they serve for , in stead of Level , and for rendring the Metals wherein they are found , more easie to work , in making them yeeld easily to the force of the wedge and leaver . Other Metals there are , wherein few of these Cutters are to be found , and if water be to be conveyed through them , there is a necessity of cutting a passage through them for that effect . Now , this Damp , whereof we speak is sound most frequently , and most violent in the first sort of Metals , viz. in these which are full of Cutters or Rifts , which gives some ground to this conjecture of its cause . These Spaces which are found in Coal , or other Metals , as Stone or Till , before the Coal begin to be dryed by a Level , are full of water , which is still in motion , as are all subterraneous springs , whereof some are more violent , some more slow , conform to the passage they have to the fountains above ground , where they discharge themselves . Now , for drying these Coals , and rendring them workable , there is a necessity to cut a passage , thorow which that water discharges it self quickly , it being large , and admitting a great quantity at once , by vertue whereof ; a great field is drained at once , and the Sourse not being able to furnish so much water , as the Conduit is able to convey , these Spaces in the body of the Metals , being emptied of Water , must needs be filled with Air , which Air having little contact and commerce , with the great body of Air above ground , and so hath little or no motion , corrupts in these places , and thereby becomes poisonable , so that when any Animal is necessitat to draw it , and respire by it , it choaks them on a sudden , just as standing Water , which being without motion corrupts , and becomes poisonable , though haply not in so great a degree as the Air : the Air , being a body much finer and purer , than Water , that holding good in it , corruptio optimi pessima . This is much confirmed by what is before asserted , that in the Coals , whence the Water is drawn , and they drained , but not by free-course , but by Force , as Pumping , and drawing by buckets , these Damps are seldom or never found : because the passage of the Water being forced , it does not so suddenly dry the Metals , as the other , whereby there is alwayes left in these Spaces some Water , which being it self in motion , keeps the Air also in motion with it , and thereby the Air is kept from corruption , at least in such a degree , as it is in the other . Hence we find , that in these kinds of Coals , the Rooms under-ground are alwayes wet , or for the most part they are so : whereas in the other , there will be no Water found to wash a mans hands : and sometimes the Coal through want of Water , becomes so dry , that it cannot be wrought in great pieces , as others , but crushes in the very working , and when wrought , is rendered useless , and will not at all burn . This puts me in mind of a very pleasant conception of a worthy and learned Person , Doctor George Hepburn of Monk-ridge , with whom I had occasion one day to discourse on this Subject . He is of opinion that the Water is the Mother of the Coal , whereby it is preserved fresh , and incorrupted , and that when the Water is drawn off , and this Damp follows , it is not the Air , which succeeds in place of the Water , and is corrupted for want of motion , that occasions it . But as we see , when the corruption of a Liquor within a Vessel , when the Mother is gone , corrupts the Vessel it self , and occasions an ill savour or taste in the Vessel ; so that the Coal being corrupted by the want of its Mother , the Water ; corrupts the Air in the subterraneous Spaces , as in Coal-Mines , Sinks , Caves , and other such like . He had likewise another pleasant conception about the generation of Coal , judging it to be formed gradually out of another Metal , as of Till , by the help of Water , of which he himself may perhaps give an account . And though I be not of his opinion in that matter , yet I must acknowledge , I was taken with it , and shall be glad to see a more full account of it from him , than he had access to do in the short conference we had .

The effects of this Damp are first , it hinders the burning of all combustible matter , as Candle , Coal , Pitch , Sulphur , &c. so that if you take a Torch lighted , and let it down to a Sink , where the Ill Air is prevalent in the time , it shall straight extinguish it . Or take a Coal , which is burning , and let it down , it shall not only extinguish the Flame , but shall make the Coal in an instant dead , and as cold as never heat had been in it . But the most dangerous effect is , its killing of living Creatures , whereby many persons have been suddenly killed . Some in going down to a Sink , where it hath been powerful , have fallen out of the Rope , and perished . Others have been choaked , and yet have gotten out by the help of others in a sudden , and have remained a considerable time without the least appearance of life , but yet have at last recovered . Yet it hath been observed , that some of these persons that have been so struck with the Damp , and recovered , have had alwayes some lightness of Brain thereafter , and never so settled as formerly . This I know to have happened to one , whom I have seen so , many times thereafter .

What hath been its effects on some Animals , whereof you have made Experiment , I leave to the account you have given . One thing I shall only mention , which to me seems somewhat strange , that notwithstanding these Damps are so effectual , and causeth so suddenly the death of Animals , yet the Ratts , which are in some of these places , where the Damps are most violent , are not reached by them . For sometimes , when they are so powerful , that nothing that lives can enter under ground , without sudden death , yet they continue there , and are not found to diminish , even where they have no access to escape , by coming above ground . Or if it should be imagined , they removed to some other place of the ground , where the Damp is not , how is it , they are not as quickly choaked with it , as Dogs are , and other Animals , which at the first encounter are killed ?

If it be inquired , how comes it to pass , that in these Fields of Coals , which are dryed fully ( as was said ) and to which these Damps are incident , because of corrupted Air that remains within the Body of the Coal , or other Metals , how comes it to pass ( I say ) that they are but sometimes incident , and are not alwayes found ? For clearing this , it is certain , that even in the grounds , where these Damps are most frequent , for the reasons above mentioned , yet they are only powerful when the Wind blows from such a certain Point , as some Chimneys , that do only smoke , when the Wind is in such an Airth . This is so generally , and well known , that the Work-men observe it , and when they find the Wind in such a Point , whence they fear the Damp , they will not enter under ground , till trial be made of the Air , which they do in Sinks , by first letting down a lighted Candle , or some burning Coals : which if they do not burn , then there is no access to enter .

Secondly , the wind in which this Ill Air is most noxious , and hurtful , blows from that Point , where the Field of Coal lyes , that 's not yet wrought , which seems somewhat strange , and yet when duely considered , it will appear abundantly consonant to reason . An example of this is to be found in the Coal of Tranent and Elphingston , the Streek whereof goes to the rise of the Hill above ground , from NE to SW , as hath been formerly observed . So that the beginning of their Level , is at the NE point of the Streek , from which the Coal hath been wrought up along the Streek towards the SW , the Wastes lying all towards the NE. Yet when the Wind blows from NE , or N , or almost from any other Point of the Compass , they are not troubled with this Damp. But if it blow from SW , and blow hard , they are in hazard to encounter it . And though the Damp is not alwayes found when that Wind blows ( whereof there may be some particular cause ) yet it is never observed in another Wind , whether it blow less or more : the reason whereof may probably be , that the Wind blowing from other Points , as from N , or NE , hath more access to enter the Wastes under ground , and move the Air that is in them , towards the face of the unwrought Coal , whence is supposed to proceed the corrupted Air , that lurks in the Rifts and Cutters thereof , ( from which the Water is drawn away , ) and occasions the Damp. Now this Air being moved by the force of the Wind , keeps the corrupt Air from coming out , it being stronger then the other . Whereas , upon the contrary , while the Wind blows from SW , it entering the empty Rooms , drives the Air under ground from the face of the unwrought Coal , down towards the old wastes , which have their course from the beginning of the Level . By which means , the Air , that is corrupted within the bowels ( to speak so ) of the Coal , comes out to the Wastes , without resistance , it being certain , that Fluid Bodies , as Water , and Air , inclines to move towards that place , where they meet with the least resistance . Hence is it , that the more direct the Wind be , in blowing against the face of the unwrought Coal , as is the Wind from NE , the Ill Air is the more repelled and driven back , but the more oblique it be , as are the Winds from these Points , that are nearest to SW , the Air is not so good and free : which difference is known by the burning of Candles , they burning with greater difficulty in these Winds , than in others , which blow from these Points nearest to N , and NE. Some are of opinion , this Ill Air ( in those places we have been speaking of ) comes from the great Wastes , that ly above the un-wrought Coal , and by strong SW Winds is driven thorow the Cutters thereof . Or the Wind blowing from that Point , and coming thorow these Cutters , brings the corrupted Air alongs with it , even as , after a showr of Rain , a spait of Water comes , and carries alongs with it , both the foul Water and the clean , it meets with . Though this may be probable , which seems to be your own opinion , yet the other seems to be more probable .

The other sort of Damp , is that which they call want of Air ; and though the term be not altogether proper ( there being no space without some Air ) yet there is a want of Air , which is sufficient for respiration of Animals , or for the burning of fire . This is ordinarily found in the running of Mines under ground , for conveying of Water from Coal , or other Metals , or in the waste Rooms of Coals , where the Sinks are very deep , and to evite the charge thereof , there is some necessity to work as far under ground for winning of Coal , as is possible , without new Sinks . The cause seems to be , that the Air under ground , in such cases , wants communication with the Air above ground , because it is found , that by giving more communication , the evil is cured . Whence comes the necessity of Air-holes in Levels , which are so many Sinks set down , for no other use , but for giving Air to the Workers ▪ Some are of opinion , that this defect might be supplied by the blowing of Bellows , from above ground , through a Stroop of Leather , or of some other thing , which must run along to the end of the Level , for keeping the Air there in motion . But I have not yet heard , that it hath been made practicable .

The effects of this Damp are not so dangerous , as these of the other . 'T is true , it will kill Animals , and extinguish burning Coals and Candles , but not so suddenly as the former ; and so people are not so readily surprized by it . The other seems to kill by some poisonous quality : in this Animals dies for want of sufficient Air for respiration . Therefore in advancing in a Coal Room , or Level where this is , you shall see the flame of the Candle grow less and less by degrees , till at last it be totally extinguished , and the person entering , shall find the difficulty of breathing grow greater , as he advanceth forward , till at last he cannot breath at all . Hence it is , that few or none are killed by this kind of Damp , and all its prejudice is , that it renders the work more chargeable , when there is a necessity to remove it .

For that , which they call Wild-fire , it being a thing not incident , but to very few Coals , is less known , than any of the rest of the accidents that follows Coals . The account I have heard of it , is , that in some Coals , which naturally are full of Oil , and that are ( as they call them ) fa●t Co●ls , there is a certain Fire , which is as a Meteor , and I judge , that from its resemblance to Ignis fatuus , which the Vulgar termeth Wild-fire , it hath the same name . It seems to be composed of some fatt oily vapour , that goeth out of the Coal , the Pores thereof being once opened , which is kindled after the same manner , as those fires above ground are , which are most ordinarily found in fatt , and marrish ground . Of this fire it is reported , that in the day time , while the Work men , are working in the Coal-roomes , it comes to no height , though it be sometimes seen in little holes of the Coal-wall , shining like kindled sulphure , but without force : but when the Work-men are once removed , and have stayed out all night , it gathers to such a strength , that at its first encountering with fire , which the Coal-hewers are necessit●te to have , by taking in of light , it breaks out with such a violence , that it kills any person , it finds in its way . The reason , why it is without this force , while the Work-men are in the place , seems to be this , that they working with such violence , and motion as they do , do certainly move the Air considerably , it being contained in so narrow a place , as a Coal-room . And this Air being violented by motion , moves that oily vapour , whereof the fire is formed , so that it gets not liberty to unit it self , being dissipated by the motion of the Air. But so soon , as the Air is still , and quiet , after the Work-men are gone home , it units it self , and gathers force , and therefore , so soon , as it meets with fire , which is more forcible , than the flame that is kindled in it , it rarifieth ; the sulphurious parts being kindled , and forceth it self out , as powder out of a Gun . For it hath been observed , that if any person stay in the Coal-sink while it breaks within the Coal-room , they are in danger of being killed . The ordinary way by which the hurt of it is prevented , is by a person that enters , before the Work-men , who being covered with wet sack-cloath , when he comes near the Coal-wall , where the Fire is feared , he creepeth on his belly , with a long Poll before him , with a lighted candle on the end thereof , with whose flame the Wild-fire meeting , breaketh with violence , and running alongs the roof , goeth out with a noise , at the mouth of the Sink , the person that gave fire , having escaped , by creeping on the ground , and keeping his face close to it , till it be over-passed , which is in a moment .

The place , where this was most known , was in a Coal be-west Leith , in a piece of Land called Werdy , which for want of Level , and the violence of that Fire , the Owners were forced to abandon .

I come now to the last part , which I promised to speak of , namely of the best way for trying of grounds , to find Coal , where never any hath hitherto been discovered , and of carrying on of Levels , for draining the Water of Coals and making it workable . As to the first part , there are but three wayes . First by sinking , which is most chargeable , in regard , that in such grounds , where the Metals are all intire , Water abounds , and this doth not only bring the Master under a necessity of great expence for drawing the Water , but also rendereth it impossible to get sinked to any deepness , which may suffice , for giving an account of all the Metals to be found , within the field , that may be rendred workable . There was a second way invented to supply this defect , which is by boaring , with an instrument made of several Rods of Iron , which boareth thorow the Metals , and tryes them . This way in my opinion , is worse then the former . For first , if the Coal ly deep , in the place where you try by boaring , it becomes almost as tedious , and expensive , as sinking , the drawing of the Rodes , consuming so much time , in regard it must be frequently done . Next , in boaring , suppose the nature of the Metals , be found , yet thereby their course can never be known , till they be sinked , which is one of the things most considerable in the search of a Coal , because thereby is known , whether it be workable , with advantage or not , and whether it be possible to draw Water from it by a Level , or otherwise . Lastly , this way leaves the Master at an uncertainty ( notwithstanding the Coal had been found ) of its goodness , as to its nature , and as to its thickness . As to its goodness , because all that is found of the Coal , by this boaring instrument , is some small dross , which remains after the washing of the thing that 's brought up in the wumble , by which none can judge of its goodness , or badness . As to its thickness , because it is impossible to discern exactly , when the boaring-instrument hath passed the Coal : all the rule for trying thereof , being the kind of Metal that is brought up in the wumble . Now , I have known in my experience a Coal boared , which the B●arer by that rule hath judged four foot in thickness , yet when it came to be sinked , hath not proven one . The reason whereof , is obvious , because the boaring-irons , being long , and weighty in lifting them up , and down , they break the Coal , already pierced ; and this falling down among the Metals , they are piercing , and being found in the wumble with them ( especially when the Metal under the Coal , is a black Till ) gives g●ound to imagine , that all that time , they have been peircing a Coal , and so consequently , the Coal must be of such a thickness .

The last , and best way of trial , is that which is termed an ranging over the Metals . For doing whereof , this method , is to be observed . Suppose there be any place within in the ground to be searched , where the course of Metals can be seen , as in the banks of a River , or Rivolet , or Sea-banks , when the place is near the Sea , then consideration must be had how far the lowest of these Metals , can go before they Crop out to the Grass , which will be known by observing the Dipp or declination of the Metals , and the Rise of the ground above , whereof a just allowance must be given , and having digged before the said Crop , you shall certainly find , the Metal , that is next under it , and if that prove not Coal , keeping the former proportion , you must advance , and digg before its Crop , and so shall you find , the next Metal under it , and so still , till you have tried your ground , and found the Crops of all your Metals within it . But if there be no Water-banks , or such like , to give you the first view , of the course of your Metals , then must you sink first at random , and having once past the Clay , you will readily overtake some Metals , whereby you will know the course of the rest , and having once found the Dipp and Rise , you must follow the method of ranging already prescribed , except the ground so to be tried , contains not within it self the Crops of the Metals , the body whereof lies in it , whether of Coal , or Stone , in that case , there is no way to try , but by sinking , or boaring . The way of ranging is conspicuous in the following figure .

Figure 11.

The piece of ground to be tried , is PN , where there are several Seams of Metals , that Cropps out at the Points KLMN . Suppose the lowest to be the Coal , viz. IN , for which you are to make trial . You Digg first at K , without the Cropp of the Seam FK , and you dig till you find the other Seam of Stone GL , at the Point C. Following the Rule before given , you advance before its cropp , and diggs at L , and finds the other Seam of Stone HM , at the point D : from which you also advance , and diggs before its cropp , at the point M , and finds your Coal at the point E. But , if by advancing over the cropps of these Metals , which comes out from under one another , you find no Coal ; then you are to range backward , for the cropps of Metals lying above these , where haply the Coal may be , as at O , and P. This in my opinion , is the most certain and exact way of trying Fields for Coal , or any other Metal of that nature , and least chargeable of all others .

The second of this last part , I promised to speak of , was in order to Levels , or Coal-Mines , which are nothing else , but Conduits or Gutters made under ground , for conveying of the Water from the Coal , and so rendering it workable . It seems that a very little time before this , that way of Mineing under ground hath not been fallen upon . For there are to be found Coals wasted in their Cropps only ; for conveying the Water whereof , they have made a Conduit , or Level , which hath been open to the Surface , like a great Ditch , some whereof have been ten or twelve fathom in their deepness .

The beginning of the Level ( to keep the term used ) must alwayes be at the lowest part of the Field , where the Coal lyes to be dryed . Some whereof , by the rising of the ground , and the Streek of the Coal rising that way ( as we shew before ) gives the advantage of a Free Level , that is , when the Water comes above ground of its own accord , without being forced by drawing . In others , there is a necessity of Engines to draw the Water from the lowest part of the Level , and bring it above ground ; which Engines are of several sorts . As when men draw with ordinary Buckets , or when there is a horse-work , or water-work , and that either by a Chain with Plates , and a Pump , or with a Chain and Buckets ; all which are very common , especially those we have in Scotland , they being capable to draw but a very small draught , making only use of one Sink for that effect . But there are to be seen in the North of England , in Bishoprick , Water-works , by which Water is drawn above 40 fathom in perpendicular , but not all in one Sink . The manner whereof is thus , there being a Sink from the end of their Level , to the surface of the earth , where their Works are going , 40 fathom deep , which must dry the Coal-Sinks at 60 or 70 , which ly above the Banks of the River , where the Water-works are scituated , there is first one 40 fathom deep from the Grass . Another in a right Line from that , of 24. Another of 12 ; upon all which there are Water-works . In the first Sink the Water is drawn from the bottom 12 fathom , and thence conveyed into a Level or Mine , which carries it away to the second Sink . By the second Work , the Water is drawn out of the second Sink 14 fathom , from the bottom , and set in by a Level to the third Sink , which being only 12 fathom deep , the Water-work sets it above ground . The form of the Engine is after this manner . In the first Sink there is an Outter-wheel moved , as other Milns are , by the Water of the River : upon the end of the Axle-tree of which Wheel , there is a Ragg-wheel , turning vertically , as doth the Outer-wheel . This Ragg-wheel by a Nutt , or Trinle turns another , which moves horizontally , the Axle-tree whereof goes right down in the Sink , and may be is 8 or 10 fathom ; at the end whereof there is another Ragg , which by a Nutt turns another Wheel , which goes vertically as the first Ragg , and causeth another Wheel with a long Axle-tree turn as the first , and so down till it come to the Wheel , which turns the Axle-tree , by which the Chain is drawn . The second Sink , hath such another Engine , but not so many Wheels , in regard it is not so deep . The third , hath only one single Wheel , whereby the Water is drawn above ground .

The most curious of these Engines , that are to be seen , are at Ravensworth near to Newcastle , which belongs to Sir Thomas Liddel , a most ingenious Gentleman , who , for procuring a Fall of Water , which may serve the Wheels of all the three Sinks , hath erected the first work upon Pillars like a Wind-Mill , pretty high above ground , from which the Water falling , makes the second go closs above ground . And to make the Water fall to the third , the whole Wheel is made go within the surface of the ground , which terminats at a River under the Works , which Mine is of a considerable length . Where Water cannot be had to make such Works go , they use Horse-works , but not with so good success , being more chargeable , and not having so much force and power , as the Water-works . But I am of opinion , that Wind-works might serve well , where Water cannot be had ; and when no Wind should happen to blow , the same Works might be supplied by Horse : and that the Wind , when it blows but ordinarily , hath as much force , as so much Water , which is made use of for turning such Wheels , is to me unquestionable . For I have seen in Holland , a Wind-Mill , that by the motion of the Outter-wheel , caused seven pair of Mill-stones to go at once , besides another motion for bringing the Victual from the ground , four or five Stories high , to be Grund . And several Saw-Mills , which besides six or seven great Saws , they caused go , did by another motion bring up from the Water great Trees like Ship-Masts , to be sawen , and placed them right against the Saw ; all which could not be but of greater weight , than 10 or 12 fathom of Chain with Buckets , or Plates for drawing of Water .

But to return , for the right making of a Level , the true hight of the ground , where the Coal lyes must be first taken , that it may be known , how much of the field can be drained by it ; which must be done , either with a Quadrant , or with an Instrument made express . Then care must be taken , to take the lowest part for the mouth of the Level , that the field can afford , and from that it must be carried in a straight line towards that part of the field , where the Coal is thought to be encountered by the Mine . In working whereof , two things are in a special manner to be reguarded . First , that the Level be wrought without ascent , or descent : the best way for trying this , being by the surface of the Water passing through it , which ought to be as little moving , as can be : for the loss of one foot of Level , which the ground gives , is a loss of a considerable parcel of Coal to be digged , especially if it be state . If there occur any Metals , which are impregnable , in the course of the Level , so that it is impossible , to follow so straight a line , in regard the Mine must be wrought over the top of that stone , which is unworkable , in that case , there is but one of two to serve the loss of Level ; either the Coal rises in Streek towards which the Mine is carried , and if that be , then after that stone is past , the Level must be carried , as low , as it was before it encountered the same , and the course of the Water shall not be obstructed , because the sourse , viz. the Coal from whence the Water comes , rising higher than the Stone , the Water shall easily pass over that hight . Hence it is , that we see in some Coals , that have been wrought , at the lowest point of their Streek by a drawing-sink , and the Streek rising from that point , the Water that hath come off the Coal , being in its Sourse higher , than the mouth of that drawing-sink , hath made it to over-run , and serve to discharge all the Water , that comes therefrom . But , if the Mine be run to a Coal , that after it hath overtaken it , rises no higher in Streek , than the Mine it self , the Water that comes from it , will not pass over any hight in its way , but will be unquestionably stopped . Therefore , in case such an impediment could not be removed , as many times such Metals will fall in , which are unworkable in a direct line , the use of a Siphon might be tried , which would unquestionably supply the loss of about 32 foot of Level , this being the hight in Perpendicular , to which the Pressure of the Air , is able to raise Water up thorow a Siphon .

The next thing to be observed in carrying on of Levels , are the Air-holes , for which there is a necessity indispensable . In setting down whereof , care must be had , that they be not directly upon the Mine , lest rubbish falling thorow from above ground , should stop , and obstruct the same , and so obstruct the course of the Water ; and therefore it 's better they be set down at a side , their only use being to communicate fresh Air to the Work-men , which if it could be otherwise supplied ( as I think it not utterly impossible ) would render the charge of the Coal-works a great deal more easy .

Other things might be spoken to of Levels , as that some run with the course of Metals , they pass thorow ; and that some run against that course ; and of bringing Level from the Dip of an upper-Coal , which hath a Level of its own , to dry a Coal lying under it , which cannot be otherwise done . But these things being common and obvious to any , who have but the smallest skill and experience , I shall forbear .

This confused account , your importunity hath drawen from me , for which if your Book suffer censure , which I grant it may do , as to this part of it , you are to blame your self , and so I rest and am , &c.

FINIS .