A short treatise of magneticall bodies and motions. By Marke Ridley Dr in phisicke and philosophie latly physition to the Emperour of Russia, and one of ye eight principals of elects of the Colledge of Physitions in London

A SHORT TREATISE OF MAGNETICALL BODIES AND Motions .

CHAPTER I.

Of Bodies Magneticall .

THAT we define to be a Magneticall body , which seated in the aether or aire , doth remaine and place it selfe in one place or kind of situation naturall , not alterable ; as all starres do , and the great regent Globes of Saturne , Mars , Iupiter , the Sunne and the Earth do ; or such as with respect and attendance follow other Globes , as the two starres which support Saturne , the foure attenders vpon Iupiter , lately discouered by the trunke spectacle , the two trauesers about the Sunne , called Venus and Mercury , and lastly the Moone , which doth follow , or go about the Earth , and respecteth the same alwayes with one pole : and therefore hath a peculiar Magneticall vertue that guideth her in this kinde of situation .

All Magneticall Globes haue some parts of their bodies which be also Magneticall , which being seperated from their proper globes , and no way hindred , will seate themselues or be seated vnto the naturall situation of their particular Globes .

The Earth , whereon we liue and moue , hath two minerals that be Magneticall , the one is the Magnet or Load-stone , which draweth iron vnto it , and this iron or steele is the other . Either of these two being conueniently , and artificially placed in the aire , or in a boate on the water , freed from all obstacle and renitency , will place and rest certaine parts of themselues , which be called the poles of their body , respondent vnto the poles of the Earth , which situation we call North and South , because they be parts of the Magneticall globe of the Earth , who by her attractiue and disponent vertue , doth thus direct and situate them .

CHAP. II

Of the Magnet stone , his forme and caps .

THe Magnet stone is heauie and massie , like vnto iron , hauing much steele and iron in it , this stone will attract , hold , disperse , and compone like a little earth other lesse Magnets and Magneticall formes of iron and steele to his conformitie of axis and poles . This stone is called the Magnet , of a countrey in MACEDONIA so termed , where plenty of them are found , it is called Hercules stone , of a City of that name , and it is called the Iron stone of drawing it , we call it the Load-stone , the Adamant stone , and the Osmound stone in our Iron-mongers shops ; because of his leading directiue and attractiue qualitie , and it is well termed the Osmound stone , because he is as it were Os mundi , the bone of the world : for by his vertue Magneticall he is like a bone and pillar whereby this world and globe of the Earth is sustained and supported in his iust situation , as the litle world of the body of man is supported by his bones .

The colour of the Magnet is like to duskish iron , of a sad browne and sanguine colour like a liuer , some of them are cole-blacke , blewish , ashey , or of a whitish colour . Some are as heauy as iron , firme and sollide , other rare porouse as a spunge , some very hard not to be cut with axe or chisell , but must be ground and fashioned on the grind-stone , other are very soft .

The best and strongest are commonly found of one intire peece , such as be of one mine and broken from the rocke are of one strength , if they be suddenly seuered ; some Magnet stones be very weake and of little force to take vp , only good to moue the Needle . The stone is not so scarce , but that in all countries one sort or other of them are to be found .

Tab: I diagrams

The first forme of the Magnet , which I offer vnto your eyes , Table I. Fig. 1. is a large one , in fashion of a round ball , boule or globe , and we do call it a Terrella , or little earth , because that vpon this figure of the body of the Magnet stone , we shall hereafter shew how to find naturally the poles and the rest of the circles of the Spheare , prouing vnto your eyes all kinds of Magneticall demonstrations on it , and shall after , most fitly and naturally , declare how to obserue them in trauelling or sailing vpon the great Magneticall globe of the earth . This forme may be artificially capped and armed with steele , or iron , at his two poles , Tab. I. Fig. 1. a. b , for to take vp iron waights , or to touch Magneticall needles withall .

The next fashion is a round and flatforme , of a reasonable thicknesse like a coite , cake , halfe boule , Holland-cheese , or part of a columne , Table I. Fig. 2. and may be called a Semiterrella his poles , Tab. I. Fig. 2. a b must be situated in the middest of the sides of the roundle . This forme may be capped artificially at either pole , Tab. I. Fig. 2. a b with two square teeth of iron , Tab. I. Fig. 2. a b , descending at right angles to the line of the axis , Tab. I. Fig. 2. a b , and this is almost as conuenient as the former in the first figure of this first Table for all Magneticall demonstrations , which are performed onely vpon a Meridian circle that passeth by the two poles , which this forme hath . And the stone for this forme is more readily procured then that is of the first and globous fashion .

The Oual and long forme like an egge , Tab. I. Fig. 3. is thought to be the best fashion , by some , for to touch the needles of the sea Compas withall , and to take vp waights at one end , Tab. I. Fig. 3. a b , because he hath a long diameter line , Tab. I. Fig. 3. a b.

The long egge forme flatted at the bottome with two iron teeth from the two poles , Tab. I. Fig. 4. a b , as the Semiterrella hath , Tab. I. Fig. 2. a b , the square formes with foure teeth from the two poles , Tab. I. Fig. 5 & 6. a b , two teeth at one end , all these are very fit fashions to take vp great waights , and to touch Magneticall bodies and instruments withall , as shall be hereafter set foorth .

There be many other fashions that may be inuented and wrought at pleasure of the Cutter , or as the Load-stone will be fittest for , as the sixth square , Tab. I. Fig. 7. the sixe angles vnequall , Tab. I. Fig. 8. The foure angles , Tab. I. Fig. 10. and of many other fashions , as Tab. I. Fig. 9. 11. 12. which may be described , all which being flatted or rounded at their poles , Tab. I. a b , hauing their caps with one or two teeth , will take vp by them both , or seuerally , and are good to touch needles , wiers , kniues , daggers , and such like long formes , to giue them vertue to take vp smaller wiers , sowing-needles and such like small waights , or to giue the vertue polar .

You may cap and arme some kinde of formes of Magnets with foure teeth , two teeth from the side flatted at either pole , as we haue described Tab. I. Fig. 7. which hath foure square iron teeth , like a foure footed stoole , to raise vp waights with foure teeth together .

If you had a Magnet stone of a flat forme , that had his poles in the center of the stone , as these I haue described haue their poles in the ends , then you might place one side with his pole downeward , and the other side vpward , and prouide you a cap for the vppermost side , like a Greeke 〈◊〉〈◊〉〈◊〉〈◊〉〈◊〉 , and a cap for the nethermost side like a Slauonian 〈◊〉〈◊〉〈◊〉〈◊〉〈◊〉 , and these being artificially and discussiuely fastened to this Loadstone , would take vp waights with fiue teeth , as it were an hand with fiue fingers .

I haue drawne a line a b in all these formes , paralell to the axis of the Loadstone , to the end that the caps of iron , crossing the poles and axis a b at right angles , may be the better perceiued .

Neuerthelesse , in fashioning of some Load-stones , the axis cannot so aptly be alwayes placed in the midst of the ends of the Load-stones being flatted , vnlesse there be a greater part of the Load stone taken away , & the bulke very much deminished , which will lessen much the strength of the stone : for the greater that the bulke is , the more is the strength of the Magnet .

Therefore I haue set downe a type in the last place , Tab. I. Fig. 12. where the diamiter a b lieth awry , and the poles be situated higher and lower at the ends , and yet the Loadstone shall take vp as much in waight as if his diamiter lay not obliquely .

The hilly knobs and angulous parts of the Loadstone may be sawen away with sand or emer● , without any hurt to the vertue of the stone , and sometimes many ounces may be cut away without any losse of Magneticall vigor , especially if any substances of other nature be intermingled and agglutinated to the Magnet , which may be knowne by their colour and hardnesse very easily .

Also , if there be any cauities and hollow places , or broken parts of the Loadstone that do diminish his vertue , or disfigure his forme , this may be supplied , mended and filled , either with a peece of another Loadstone , or with a cement of the powder of the Loadstone , and the filings of steele or of iron brayed and grinded very small vpon a painters stone , mixed with rozen and waxe , melted and coloured to the colour of the Magnet that is mended , putting into this cement more or lesse of the filings , according to the strength of the Loadstone . Some with this cement , and such like glutinous matter , make diuerse formes of Magneticall bodies artificiall .

It is very conuenient for makers of sea-compasses , and maisters of ships to haue a Magnet well capped , that taketh vp at one end halfe a pound waight at lest , for it is not wholly necessary that the same should be of the best vigour and strongest rocke : for all Loadstones , both of great and lesse vigour , haue the same facultie Magneticall to all intents and purposes . The greater stones of the same rocke haue a larger vertue then the lesse , and euery part and small peeces of Magnet stones haue euery one of them the same vertue and vigour Magneticall the great ones haue , sauing that they be more weake , and not alwayes proportionable in strength vnto them .

CHAP. III.

Of Jron .

IRon is a mettall decocted out of the Loadstone , or out of a mine of that kind . The best iron-mine and Loadstone is all one thing and body Magneticall , for it being placed artificially , either in the aire or vpon the water , moueth North and South , attracteth other iron vnto it , and performeth the same conclusions that the Magnet stone doth .

This mettall is heauie and of a blewish blacke colour after that it is tried from the drosse , and is made of certaine iuces and vapours in the conuenient bowels of the earth by a specificall vertue working him . Besides the mine this mettall is excocted out of diuerse stones , sands , earths and clayes of diuerse colors , which haue much Iron like matter in them .

If some clay 〈◊〉 burnt in the fire , being of a long forme , cooling North and South , after being hung on 〈…〉 in the aire , or put into a dish in the water , it will turne and moue it selfe too and froe , till it rest North and South , and some clay being burnt , will shew a little iron vpon his sides that was melted out of him , so that this Magneticall substance of iron is not very scant to be found : for in all countries and regions there is great store of this mettall , being the principall matter of the externall barke of the globe of the earth .

Steele and iron are the best Magneticall materials for Magneticall vses ; because by the Smithes skill they will be extended and fashioned into diuerse formes , fit for the practise and vse of Magneticall demonstrations . Of this mettall are made caps for Loadstones of diuerse formes with teeth , to take hold of , and lift vp great and small fashions of waights of iron , and diuerse other Magneticall needles and formes .

Tab II diagrams

It is good to haue long plates of iron reasonable thicke , Tab. II. Fig. 7. round plates of iron , Tab. II. Fi. 9. and round rings of iron of diuerse weights and bignes , Figure 8.

It is conuenient to haue diuerse directory Magneticall needles , great and small , Tab. II. Fig. 10. 11. for dyals and instruments , and needles for Compasses , Tab. II. Fig. 12. & 13. to fasten to the Cardes , or to take off at pleasure : we vse short wiers fastened to thrids ; and a little Loadstone in a thrid to take vp a waight .

Also it is necessary to haue Inclinatory-needles , Tab. II. Fig. 16. to put into his ring , and a short one with a Lute-string in the middest , Tab. II. Fig. 17. or else put in a frame of brasse or siluer , as Tab. II. Fig. 18. to find the pole of the Loadstone , and to demonstrate his oblique inclination to the Loadstone , as he is caried about him , or else to haue a little round Loadstone put into a frame with an axletree , hauing his poles marked Fig. 19. which applied about the Loadstone , turneth and conucrteth it selfe diuersly , also it is fit to haue a short and thicke needle , Tab. II. Fig. 20. into the end of it , there is to be put a wier of filuer , brasse , or of a peece of a Whale-bone , for vses hereafter to be declared . Also a long wier thrust through a corke , Fig. 21. serueth for Magneticall vses in the water . These formes of iron , with others that the ingenious will easily inuent and make , are very fit for Magneticall demonstrations , as well as the variety of Magnet stones are .

CHAP. IIII.

Of the Earth .

THis great Globe of the Earth whereon we moue and trauell , is found to be a Magneticall body , by such as haue trauelled and sayled round about her , as Sir Francis Drake did , and M. Candish , whose Magneticall Compasses were alwayes directed Magnetically , that is , the Lilly of their Compasses was turned alwayes towards the North-pole in all places wheresoeuer they sayled , by the vertue Magneticall , and disponent faeulty of the Magneticall Globe of the Earth , as it is demonstrated in the XXV . Chapter of this Booke . Also by such as haue made their course northerly and southerly , it hath bin obserued that the Magneticall Inclinatory-needle doth in euery eleuation of the pole conforme and apply it selfe , or rather is conformed and disponed vnto the axis of the Earth , according vnto certaine correspondent angles to the Latitude , as it is demonstrated in the XII . XIII . XXXV . & XXXVI . Chapters of this Booke , whereby it is demonstratiuely to be concluded , that the Earth is a Magneticall body , directing both her selfe and the other two Magneticall bodies into the North and South , by the vertue of her Meridian circles and parts , as is demonstrated in the IX . chap. and others .

Moreouer , the Earth hath naturally two Magneticall poles , vnto the which these meridionall parts do direct , bend & force , not only Magneticall bodies neere the Earth ; but also her owne mighty and massie situation , stability and firmenesse , and seateth her selfe so strongly vpon her two poles , by her naturall and Magneticall vigor , passing from her meridionall parts to the poles , as if she were tied by many mighty strong cables vnto two most firme pillars , farre stronger then any Hercules pillars , not to be remoued by any force from her naturall position ; which thing , if it might chance that it should come to passe , yet certainely she would returne againe vnto her former firme seate and place , as all Magneticall bodies and directory needles do , as is demonstrated hereafter .

Thus we proue that the Earth is placed and firmed by her Magneticall vertue , and not by her grauity and waight , though that the parts of the Earth do conioyne and adhere together by their grauity mouing to their Center . But the Magneticall nature moueth , conformeth , and firmely seateth it selfe to the poles and Axis .

Now for that the poles of the Earth do alwayes , by their natural vertues hold the Earth North and South in one certaine and vniforme situation , eleuation and place , there is no doubt but that the whole globe of the Earth , inwardly stored with many materials and rich minerals , & outwardly adomed with many trees and excrescences , all for the vse of man , with liuing creatures innumerable , as also in reason it is an vnfallible certainty , that the Earth hath , at her first creation , bestowed vpon her a globous and starlike vigor , or intelligence , whereby she may , hauing her whole parts vnited together , by the vertue of grauity vnto the center , and her place made sure Magnetically by her poles vnmoueable ; yet moue naturally , keeping her place circularly & diurnally out of the West into the East , to the end that all creatures should receiue the comfortable and liuely beames of the Sunne , and the influences of the rest of the Planets and Starres .

This motion many learned men haue attributed vnto the Earth , for the benefit of calculating the motion of the Planets the better , which naturally she hath in her selfe ; for euen as it were needlesse for a wheele to haue her naue , spokes and rimme about her , if it should not be vsed to turne about ; so it were to no purpose that the Earth should naturally haue a globous body , two poles , an axis , meridians and aequator , as shall be demonstrated hereafter , parts fit for circular motion , and not for to turne her aequator and paralels about , as the wheele doth .

Although these arguments will hardly perswade vs to beleeue the earths motion ; yet because that it is lately obserued vnto our sences by helpe of the trunckespectakle , both by Galileus and Kepler , famous Mathematitians , that the great body of the globe of Iupiter , being twelue times greater then the Earth , doth turne about in lesse time then a day vpon his axis and poles , who also haue obserued foure Moones , attendant on Iupiter , which moue round about him , the slowest in 14 dayes , the next in seuen dayes , and the rest in shorter time . So likewise Iohn Fabricius hath obserued , that the great globe of the Sunne , hauing three great spots , like continents in him , and being sixty times greater then the Earth to moue about his axis and poles neere the time of ten dayes , or there abouts , so Galileus and Kepler haue seene the Planet of Venus to moue about the Sunne in ten moneths , and to haue her light from the Sunne in this time increased and diminished vpon her body , as we see the Moone here neerer vnto vs to haue ; therefore it being certaine by obseruation , that the globe of Iupiter and the Sunne do turne about their axis and poles , whose materials we know not , we need not doubt that the Earth should haue a circular motion for her great good . But how the Earth doth turne circularly we cannot well see it , with the sence of our eyes , vnlesse we had them placed in another globous body and starre , as if they were in the Moone , where we might see the spots of the Earth to turne about , as well as now we see the spots in the Sunne , and Iupiter to moue circularly in their place . And as contrariwise our eyes here on the Earth do see that the Moone doth not turne about , by the placing of her spots , alwayes in one fashion vnto vs : for we may obserue with our eyes , that the Moone hath poles of a kind of Magneticall nature , which do alwayes hold her to behold the center of the Earth , and so stayeth and conformeth her , that howsoeuer she moue , higher or lower , or wheresoeuer she be , yet alwaies the spots of halfe her globe be alike apparant vnto our eyes , and conforme her to behold the center of the Earth with one pole : neither doth the Moone turne about her body vpon two poles , as the Earth doth vpon hers , but is kept firme and vnmoueable from circular motion , about her axis , by other two poles that be vpon the edges and aequator of her body , because her spots be alwayes alike on her East and West side , that hold her firmely & stiffely that she can by no meanes turne about vpon her first two poles : For it is the vertue polar and Magneticall that holdeth all globes in their position whatsoeuer . Besides , the Moone hath another vertue giuen her at her first creation , whereby beholding alwayes the center of the Earth , and mouing neerer and further from the Earth , as tied with an axletree , she moueth , slideth , and passeth monethly about the Zodiacke , that all the parts of her globe may be illuminated and refreshed with the beames of the Sunne , and influences of the Starres : for as a ship vpon the water is directed euen forward by the sterne and ruther , which hath not only a right line to direct forward , but also a right angle descending downewards , that she waue not sidelings or turne about ; yet hauing this position , if ankors be layd out , either forward , or backward , or sidelings , with their cables on boord , if there be force or vertue on boord to hale forward , she moueth forward , if drawne backward , she goeth backward , if pulled by the cable on the left hand , yet keeping her position , she betaketh to that hand , and so to other parts . Euen so the Moone being seated , as afore is said , doth moue on her axis , higher or lower , on this side or on that , according to the vertue & strength of the multiplicity of her axletrees , being her limbes to stay and moue withall , as the body hath armes and legges , with variety of muscles to moue on all hands .

But the Earth , whereon we liue and trauell , hath neuer bene found by any to haue any poles in the aequator of her body , or neere the same : for if we were so happy to find any in the East or West of the earth , then the matter of longitude would be perfectly attained vnto , which hath so greatly busied all the ingenious wits of the world : and therefore we affirme that the Earth doth turne about , because there are no poles in the aequator to hinder her , as there is in the Moone from circular motion . But leauing these motions to others that do labour more therein , here in this booke I purpose onely to intreate of the great globe of the Earth , as she is a Magneticall body , which shall be first performed , by way of imitation , in a little Magneticall earth , or Terrella and Semiterrella , made of a round Loadstone and Adamant , whereby we shall plainely and sensibly demonstrate , that there be two poles , an axis , meridians , paralels , and an aequator in euery Loadstone and Magnet , and we shall produce many other pleasant demonstrations , manifest Theoremes , and sensible practises vnto your eyes and vnderstanding , which we shall after illustrate to be in the globe of the Earth , to proue it to be a third Magneticall body , different in substance from the other two Magneticall bodies , spoken of in the two former Chapters .

CHAP. V.

Of the two Poles , and how these points are found out .

THe ancient Mathematitians and Astronomers of formes times , obseruing the diurnall motions and apparences of the Planets and Starres , fained certaine fixed poles , and other circles in the heauens , by which they discoursed of the risings , settings , motions , and of the places of the planets and starres ; neuer imagining that these fained matters were naturally and sensibly to be found in the globe of the Earth , much lesse to be seene naturally , and in a round Loadstone , and in all other formes of the Magnet stone , being long seuered and kept from touching and couching in the bowels of the Earth .

I will first proue how the two poles are found out in the Magnet stone , which are very necessary to be knowne , before that the Load-stone be fashioned into any forme , for the better proportioning of the same ; and this matter may be accomplished sixe or seuen manner of wayes .

The first way is to role the Load-stone in small and cleane filings of iron , and about those parts where the points and poles be , there the filings will cleane fast in great multitudes , and at the pole will stand and be erected vpright , marke these places with Chalke , Tripoly , Red-oker , or with an hard file for the poles .

The second way is to hang a sowing-needle by a thrid , or a small wier , Tab. II. Fig. 3 14. or as in Table III. Fig. 1. ouer those places of the Loadstone whereabout the poles are likely to be , and the needle and wier will moue from his perpendicularity , and hang directly ouer the point , and desire to touch the pole . So likewise , if there be a small peece of a Load-stone , Tab. II. Fig. 15. cemented to a thrid , and held so that one of his poles bend downewards , and it will affect to touch and to vnite it selfe to to the contrary pole in the stone .

Thirdly , take the needle of a dyall , or some of the directory needles , before described , Tab. II. Fig. 10. & 11. place the same , being touched Magnetically vpon his pin or stake , Tab. III. Fig. 1. then turne the Loadstone round about , holding it somewhat neere vnto the needle , and it will point at the pole of the Magnet , desiring to touch it .

Fourthly , take a peece of small wier , of iron or steele , such as is made for Virginall-strings , Tab. II. Fig. 6. and cut off a part as long as a barley corne , and set it vpon the Load-stone , and it will sticke fast at one end vnto it , but erect it selfe ▪ at the other end , and being put forward , will stand vpright onely there , where the pole of the Magnet is , Tab. III. Fig. 2.

Fifthly , take a little Inclinatory-needle , before described , Tab. II. Fig. 17. that hath a Lute-string put through him , or take that Inclinatory-needle which is placed on a frame , and borne vpon an axis , Tab. II. Fig. 18. and cary either of these round about the Loadstone , and they will conforme themselues obliquely vnto the stone , and onely at the poles will direct the points of their ends perpendicularly ouer the same . Also take the litle round Magnet , before placed vpon his axletree and frame , Tab. II. Fig. 19. hauing his two poles marked , and this stone will turne and conforme it selfe to the Loadstone , and apply his contrary pole directly ouer one of the poles of the Loadstone .

Sixthly , place a small wier vnder the Loadstone , and it will follow to the pole thereof , and cleaue and hang to the pole it selfe , which is to be marked .

Seuenthly and lastly , take that wier that is thrust through a corke , Tab. II. Fig. 21. and put it in water , holding a Loadstone vnto it , and it will draw neere , and bend it selfe to ioyne to the pole of the Magnet .

If a stone be diuided and sawen in two parts from one pole to the other , or by a paralell , Tab. III. Fig. 3. the poles will be in their paralell place , Tab. III. Fig. 3. a b , and are to be found in the middest of the substance of the Loadstone , vnlesse they be drawne aside by excrescenses and leuities .

CHAP. VI.

Of the vertue of the Poles .

Tab: III diagrams

Magneticall bodies haue two poles or points , the one is North , and the other is South , which be knowne either by hanging a Loadstone leuelly in a third , or putting it in a wodden dish to swim in a basen of water , and then the one Pole will alwaies turne to the North , and the other to the South , which are to be marked accordingly .

But whether that Pole that seateth it selfe South or North may be termed by that part which it respecteth , some haue laboured much to cleare . If you chance to find out the rocke where the Loadstone doth grow , where you purpose to take out a part of the same , marke your part with notes for the North and South , then cut out your peece out of the rocke , and put it into a bole to swimme on the water , and your markes will be turned to a contrary situation , to that they had in the rocke , and the North note will be turned South , and the South North , and so would the rocke of the great Magnet it selfe , if it were so placed , make the like alteration in his situation , by the generall conformation and direction of the mighty Magnet , the globe of the Earth . Therefore the reason why that the Loadstone in the boat vpon the water , turneth , bendeth , and seateth it selfe to a contrary situation , to that he receiued and had primarily , whilest he was in the bowels of the Earth , and vnited with the body of the great Magnet , is because that euery peece and part of a Load-stone , being seperated from the whole whereof he was a part , is now become a perfect , complete , and sole Magneticall body , and is as it were , a little earth of it selfe , hauing all the proprieties Magneticall that the great Earth hath , as his two poles , meridians , aequator , and such like : and therefore according vnto the nature of Magneticall vnion , hereafter spoken of in the XXII . chapter , will in no wise indure , and cannot be suffered to match and seate it selfe as he did before , but thinketh it more naturall , and a thing of more perfection and conueniency to turne his aspect a contrary way , to that he had primarily at his first making and endowement with Magneticall vertue .

This alteration of polity is to be obserued likewise in Magneticall needles , and long peeces of iron that be touched , and animated , and adhere to that part of the Load-stone , which seateth it selfe North , which being at liberty and seperated from the Loadstone , will turne that part and end that was touched at the North pole , and seate it alwayes in the South , and it shall be sufficient for vse to know and marke with a note which is the North-pole of your Magnet , and which is the South-pole .

There is another vertue in the Poles of the Loadstone , and that is , that the South-pole turned downeward , will take vp more then the North-pole will , and the North pole will erect a greater waight th●n the South part or pole will , as some say , Tab. III. Fig. 2. a b. But I haue alwayes obserued , that the Pole of the Magnet that seateth it selfe North , is alwayes the most vigorous and strong Pole to all intents and purposes : vnlesse he lacke the quantity and like substance the South part hath .

These Poles which be in the great Magnet of the globe of the Earth , haue a maruelous strong Magneticall power imparted vnto them , that they cannot be turned either higher or lower , or moued to the right hand or to the left , but hold the Earth continually in a true and certaine position and place , and would if any force or power should moue their great strength awry from the true syte and meridian latitude , returne to their right syte and place againe , and this is the true vertue of the Poles of globes , which the Sunne and Iupiter haue as well as the Earth .

These Poles be most certaine and sure markes for all Magneticall bodies , conueniently caried to direct themselues vnto , Tab. III. Fig. 9. as appeareth by our Compasses , which in all places of the world turne their Lilly into the North , whereby the Marriner knoweth what course to take . And the Magneticall Pole , & Poles of the world , both articke & antarticke , are all one and not diuerse , as some haue imagined , which haue lost both their oyle and their paines ; and this is true , by the demonstrations and motions of the Inclinatory-needle , although there be many momentary causes of variation .

These Poles hold the Earth certainely in her polar position , while she turneth her selfe about to receiue the Sun-beames , and influences of the starres and planets , for the generation and maintenance of all inferior bodies , vpon her , in her , & proceeding out of her .

Lastly , these Poles of the Earth , in certaine great number of yeares , haue naturally a little inclination in the polar circles of the Zodiacke , for the receiuing and moderation of the beames , lights , and influences of the starres , whereby the progressions and anticipations of the aequinoctiall , and the mutations of the greatest declination of the Sunne are perfectly vnderstood , to preuent the faining of many Spheres aboue the starres , as the ninth , tenth and eleuenth , and their impossible motions .

In fashioning the Loadstone , it is conuenient to make flat or roundish the ends of the Magnet , where the Poles are the better to cap and arme them with iron or steele , to lift vp their conuenient waights , Tab. III. Fig. 2. & 12. and as the most are , Tab. I.

At the Pole the Inclinatory-needle doth not incline obliquely to the axis , Tab. III. Fig. 6. as the needle c c to a b the axis , as in other places , but aspecteth the Pole directly and perpendicularly , as Tab. III. Fig. 1. the needle c respecteth the axis b a directly , & maketh one line with it .

Also at the North-pole that point of the directory-needle , and compas , that did behold the South of himselfe , being applied to the North-pole , doth turne , as some thinke , but this is true only at the aequator in the spaces between the aequator & the 34 degree , as is demonstrated in the XII . chap. & not at the Pole it selfe , and the places neere adioyning : for at the North-pole , if the Magnet be truely placed , that point that pointeth towards the South , doth point to the South directly , and in the places neere adioyning doth it obliquely . A wier touched Magnetically hath two Poles , as Tab. III. Fig. 5. the one end a is North , and b of the nature of the South .

CHAP. VII .

Of the Axis .

THe Axis or axeltree of the Magnet , is a line that passeth from the one Pole to the other , by the center of the body of the Loadstone , and after this order there is an Axis ▪ vnderstood to be in the Earth , Tab. III. Fig. 1. 2. 3. & 9. 10. In fashioning of Magnets , if a peece be taken away paralell from the Axis , then in these two Loadstones the Axis with his poles will be remoued into the middest of the stone , as Tab. III. Fig 3. a b , the Axis in either peece is in the middest of the stone , so whether that bunches be taken away from the Loadstone , or any cauities filled , the Axis will alwayes be placed in the middest of the most vigorous bulke of the Load-stone , as a b in euery figure .

It is said in the latter end of the V. chapter , that if a Loadstone be sawen in two parts , from one pole to the other , vpon the Axis , that the poles and Axis will be found in the middest of the bulkes of the two peeces paralell to the old Axis , Tab. III. Fig. 3. and the poles of the lesser peece will be altered .

Also when as a side of the Load-stone shall be made flat and paralell to his Axis , that side will attract , hold and vnite vnto him long peeces of iron sidelings and paralelly , Tab. III. as Fig. 4. c the peece of iron is adioyned paralelly to a b the Axis , as the pole erecteth perpendicularly to it , Tab. III. Fig. ● . the waight c is attracted plim-wise to the Axis a b. And also two Magnets somewhat long , in forme swimming in their vessels vpon the water , wil adhere and vnite in a meridian paralell to their Axis , Tab. XI . Fig. 5. that if one of their vessels be haled , the other vessell with the other Magnet his loading will follow , both being fast grapled together , so that they cannot part asunder .

Likewise , take two Magnets , that be armed with their teeth of iron or steele , descending from these poles at right angles to the Axis , to take vp , with both teeth together , & haue their Axis both of one length , as Tab. III. Fig. 12. place the teeth descending from the South-pole , vnto the teeth that haue the vigor from the North-pole , and they will cleaue and vnite together as one body and Load-stone paralell-wise to the Axis , and the one , though he be the weaker , will lift vp the heuier perpendicularly .

Also all Magneticall bodies , whether it be at the aequator , at the poles , or at any intermediall part , betweene these two , do all of them apply , conforme , and vnite their bodies together , according to a correspondency of their Axis , as shall be declared hereafter , and not with their center to the center of the others body .

If a wier be touched Magnetically at one end , the vigor will run through all the wier , or Axis , and haue a contrary vertue in the other end , the one North , the other South , and halfe the Axis will be of one nature , and halfe on another , Tab. III. Fig. 5. the end of the wier at a is of the nature of the North-pole , and the end at b is of the South-pole .

We sayd in the IIII. chapter , that the Moone doth alwayes turne one Pole of her body toward the center of the Earth , and moueth neerer & further from the same , as if that a long axeltree were passed through her body , & fastned in a ioynt to the center of the earth , on which she should make her Epigeum and Peregeum ; in like maner , it is to be probably gathered , that the earth may naturally haue a Helicall & Spirall vertue to moue on the Cilinder of her Axis in spirall lines , not vnlike the arches of the longitude of the day , to performe the Zodiacall motion , partly illustrated in the XXII . chapter by the bead , in an instrument of rings for the finding of the variation , where the bead , as an earth , is placed in the Axis , higher and lower , according to Zodiacall direction , and Magneticall vertue will permit this spirall motion , like as the sap passeth in the earth from the North hemisphere , to the South prouince .

It is a thing worthy of better obseruation from the Truncke-glasse , to know whether the Axis of Iupiter and the Sunne be paralell one to the other , and with the Axis of the Earth , which is to be examined by the turning of the spots about .

CHAP. VIII .

Of the Aequator .

IN all Magnetical bodies there is an Aequator , or middle fence , that diuideth the whole body in the middest betweene the two Poles , like a middrift , into two equall parts , hemispheres , and prouinces : outwardly in the middle part in the greatest circumference from the poles , there is an Aequator , circle , or line , that deuideth the North-part of the stone from the South part , as by a border-marke , so that if a directory-needle touched Magnetically , be conueyed to any part betweene this Aequator and the poles , presently the end of the needle that is of the nature of the other prouince beyond the line of the Aequator , will turne about from that part , and the other end of the needle that hath affinity and naturall conformitie with the pole of that prouince , will offer it selfe , as Tab. III. Fig. 6. 7. 9. 10. in the prouince of the North-pole a aboue the Aequator and pricked line , the bearded ende of the needle doth only offer it selfe , and desire to apply and vnite to that part , but the crosse end of the needle wil flye from it ; so this crosse end of the needle will only affect to behold the south prouince vnder the Aequators pricked line to the pole b , and the bearded end of the needle will shift away . This assertion is not only found to be true in the Loadstone , but also in other formes of iron and steele , and in the great Earth it selfe . As take a round plate of iron that hath laine some time quietly without stirring , as Tab. III. Fig. 6. or a ring of iron , Tab. III. Fig. 7. and offer the sides of this plate , or ring , vnto the needle , turning them about , and the bearded point of the needle will respect the one halfe of these iron circles , and the crosse part of the needle , being of the nature of the other semicircle , will apply and haue respect thereto . Here in these iron formes the Aequator and limit of the two semicircles , is better perceiued where it should be marked , then the poles are : for when the Magneticall needle is once past the bounds of the Aequator , presently he turneth about his other point that respecteth the contrary semicircle , or rather hemisphere , the which for distinction sake might be painted of a red colour .

Moreouer , if a directory-needle , or Marriners compas be placed neere the Aequator of a Loadstone , of these iron formes , or of the earth , they will situate themselues paralel to the axis of the poles , as Tab. III. Fig. 6. 7. and Tab. VI. Fig. 1. Tab. VII . Fig. 1. 2. and incline neither to one pole , or the other , being placed in a right sphere , where the poles lie in the Horizon , the needles standing in equall ballance with the Horizon , looking North and South , paralell to the axis .

Whereas it hath bene declared in the VI. Chapters before of the vigor of the poles , that the vigor and strength Magneticall proceedeth by little and little from the Aequator to the poles , increasing in their passage by the meridians vnto the poles , to the end to augment their vertue of retaining , & consisting most firmely and constantly in the North and South , wherby the Aequator of the earth is left voide of all vertue of consistence , and left free , or rather depriued of constancy and retaining of any firme situation , and remaining naturally , by reason of his great circumference and weake renitency , most apt and prone for circular motion , which by her star like vigor and intelligence , hauing this her globous body so firmely fastned naturally in her poles , as it were in two strong pillars , and fitted in the Aequator and paralels , as in Chariot-wheeles : for circumuolution turneth her selfe daily about from the West into the East , to meet with , and receiue the pleasant beames and influences of the Sunne , Starres , and Planets , for to cherish , comfort , and inuigor all those goodly creatures that be placed vpon her , grow out of her , or be bred and conceiued in her , as also for the continuall change and vicissitude of seasons , being a thing more naturall and fit that the earth should thus moue for her owne good , then that all the heauens should furiously moue to serue her .

It is to be obserued in fashioning of the Magnet stone , that when the axis of the same shall be cut shorter , that then the Aequator remoueth necessarily to the middest of the body of the Loadstone , as if a long Magnet should be sawne and deuided into two peeces , as Tab III. Fig. 8. vpon , or paralell to the Aequator , the poles will be in the middest of the stones , and the Aequator will also be in the middest of either stone , as a b , and the pricked lines be .

For euery peece and part of a Loadstone hath his poles and Aequator , with the rest of the circles , as well , and as naturally as the earth , or any great Magnet hath , and will be deuided into two iurisdictions by his Aequator though before all his part was but of one prouince and nature . Euen so if you part a needle , or long , wier Magnetically touched , in two peeces , the parts will haue their seuerall poles , as Tab. III. Fig. 5. the poles a b are in either part of the wier .

CHAP. IX .

Of the Meridians .

THe Meridians be great circles drawne by the aequator vpon the Loadstone , or as may be obserued by the needle vpon the face of the Earth , from the one pole to the other , where they do all touch , as in the centers , Tab. III. Fig. 9. they be naturally in euery Loadstone , and in the earth , and are thus found out : for they be the pathes whereon all Magneticall motions are trauersed and directed . Lay a wier of a reasonable length vpon the Magnet , as Fig. 9. a b , and it will turne and seate it selfe vpon a Meridian , and point to the poles , and if he be moued from the Meridian by any force , he will soone returne to the same againe , and by this wier you may marke out a Meridian ; Likewise take a little directory-needle of a small diall , and set it vpon a small pinne with a foote , setting them vpon the Terrella , Semiterrella , or any Magnet , Tab. III. Fig. 9. and the needle will point towards the pole , make a marke , remouing the needle forward , and make more , then ioyne all the points together , which make a part of a Meridian , and being continued forward runne to the pole , so a small and short wier placed vpon the Magnet from place to place betweene the aequator , and the pole , will sticke fast at one end , and erect the other obliquely , and the seuerall places , being noted with chalke or emery , will set out a Meridian to the pole , at the aequator , being no longer then a barley corne , will lie flat to the stone , put him forwards toward the pole , and then he will erect himselfe a little , sticking at the other end vpon your Terrella , Semiterrella , or Magnet , put him more forward , and he will be erected lesse acutely , and about 34 degrees from the aequator , he will make a right angle with the axis of the Magnet , and being brought and placed vpon the pole , standeth vpright in one continued axis , with the axis of the Loadstone , Tab. III. Fig. 9. This variety of application to the Magnet , doth produce a certaine kind of motion Magneticall , which may be called the motion of inclination , conuersion , or conformity of one Magneticall body vnto another ; but the little directory-needle demonstrateth this motion best , being caried about the Terrella and Semiterrella , as shall be demonstrated in the XII . Chapter following .

I haue , spoken before somewhat as concerning the making flat of a side of the Loadstone , paralell to the axis , which is a Meridian line paralell thereto , whereby waight may be apprehended , Tab. III. Fig. 4.

Therefore hauing a Magnet stone first made flat at the ends , where the poles are , and after a side made plaine and straight , paralell to the axis for a Meridian , then you may forme the stone into what fashion you please , as into a foure-square , into a figure of 5 , 6 , or 8 equall angles or sides , or into vnequall sides , as hath bene thewed in the first Table in many types .

Cut a part from a Magnet stone meridionally , and that end which was placed South when it was whole , being seuered , will turne North , though naturally at first it was the South point , as in Tab. III. Fig. 3. the poles a b in the little peece are turned contrary to the poles a b in the greater Magnet .

CHAP. X.

Of the Paralels .

THe Paralels be circles and parts equidistant from the pole , and Paralell to the aequator , and do possesse the whole space betweene the aequator and the pole , as Tab. III. Fig. 10. these circles are pricked out , as the aequator is , and are found by the Inclinatory-needle , being caried at one angle about the Terrella , and in all these places the small wiers , Tab. III. Fig. 9. and directory-needles , Tab. III. Fig. 10 do apply their axis or line of length obliquely to the axis of the body of the Magnet a b , or of the earth .

For to find out these oblique angles in euery Paralel , and what correspondency they haue vnto them , there be diuerse operations , diagrammes , instruments , and calculations found out to demonstrate , and to know what angle of inclination will answer to euery Paralell : for in euery Paralell of the earth the Inclinatory-needle maketh a diuerse angle of inclination to the axis , but one angle , and of one sort , in one and the same eleuation of the pole or Paralell , and by this meanes of the Inclinatory-needle in a ring , the latitude of the pole is knowne on both sides of the aequinoctiall , without any sight of the Sunne and starres , by the Magneticall disposition from the earth .

If in forming of the Loadstone , some Paralels be cut away , as it should seeme in the Terrella , by cutting and flatting the end where the pole is , Tab. III. Fig. 11. yet in truth they remaine still vpon the Magnet , though the Meridian lines be changed from crooked lines to straight lines , and this is to be obserued , that alwayes the Paralell neere 34 degrees in the perfect Terrella , Semiterrella , and round Meridian , or straight Meridian , where the directory-needle aspecteth , that edge , or angle , at right angles , vnto the axis , Tab. III. Fig. 11. and Tab. VII . Fig. 2. as the most protuberant and middle place betweene the pole and the aequator , as in this Load-stone truncated and flatted at the pole .

In the Paralels of like distance from the pole , all Magneticall bodies do apply and conforme alike , and haue the like inclinations of their axis , that denotate like eleuations of the pole , and do attract and retaine with like forces and vertue , Tab. III. Fig. 11.

Place two wiers vpon a Paralell of the stone , as you would say East and West , and they will not conioyne or vnite together , Tab. III. Fig. 11.

Rub the needle of a dyall Paralell-wise on the Loadstone , and it will hardly be excited and animated , vnlesse the touching be neerer vnto the pole .

CHAP. XI .

Of the Horizon .

THe Aequator , the Meridians , the Paralels , the Poles and Axis , are all naturally in the Globe of the Earth , and in euery Magneticall body , and not imaginary in the heauens , as Astronomers heretofore haue thought , not knowing in what body to find them naturally . Now it remaineth to write of the Horizon , which is a great circle that deuideth the Globe of the Earth into two hemispheres , or into two equall parts , like as the aequator doth deuide the Magnet into two prouinces , and though that the Horizon be of great vse in Magneticall practises ; yet I cannot affirme that the Horizon is naturally in the Earth , or any other Magneticall body , as the aequator is , onely euery point and place vpon any meridian and paralell may be the center of the Horizontall circle , which center is Magneticall , and of many vses in Magneticall demonstrations , both to know on what paralell and eleuation of the pole , aboue the Horizon the inclination and conformation of the Inclinatory-needle is obserued , whereby we come to the knowledge of the angle that inclinatory maketh with the Horizon , in euery paralell of the earth , and by a respondency that it hath with the axis of the eleuation of the pole we come to know , as hath beene sayd , the latitude of the pole in all places of the world , without the vsuall helpe of the celestiall bodies , hauing as certaine an helpe from the materials of the Globe of the Earth , and their vigor for this conclusion , as from any other globe whatsoeuer .

This center of the Horizon also is the place whereon the Pilot placeth his Compas , and composeth the same leuelly and parallelly to the circle of the Horizon , so that by the firme direction of the Lilly of the Compas to the North , he knoweth which way to steere his ship to the desired port .

The Horizon therefore of vse is a plaine and paralell superficies vnto the horizontall circle it selfe , and is to be deuided into 360 parts , from which lines are to be drawne to the center of this horizontall circle , and may be called the lines of position , verticals , and Azimuth , whereof one of them is of principall note , and is called the Magneticall meridian line , from whence the rest are to be numbred , and by which we are helped to knowe the declination of the Marriners Compas from the true meridian of the world , which thing is commonly called the variation of the Compas . For although that naturally the directory and Magneticall needle , or Compas , should place it selfe vpon the true meridian , by the disponent vertue of the Magneticall globe of the Earth , yet by reason of the neighbour-hood and approching of other eminent , forcible , and great Magneticall continents , this needle is turned awry from the true meridian and varieth , and declineth to the one side or the other , certaine parts and degrees to be reckoned vpon the horizontall circle .

Whereas it is sayd by some , that the horizontall circles make alwayes right angles with the axis of the earth , this assertion cannot alwayes be true , but this circle of the Horizon maketh alwayes a right angle with the meridian , whereon he standeth .

CHAP. XII

Of the two circles that the Needle maketh about the Magnet .

HAuing explained before the nature of the poles , the axis , and the circles , and parts of the Magnet to be naturally in the same , and in the globe of the earth ; Now it followeth that we demonstrate how the Magneticall needles and wiers doe conforme themselues to the meridian of the round Magnet , whether it be a Terrella or Semiterrella .

For this purpose it is very necessary to haue these formes truly rounded , to be caried artificially vpon a foote , and fitted within the head of the same , in a circular and hollow cauitie , that may receiue the stone , so that the two poles of the Magnet do lye leuell with the Horizon , leauing a thin ring of the foote about the stone , vnder which there is a shoulder , a quarter of an inch thicke , left of the abatement of the height of the foote round about , to beare a round verge or limbe of past-boord , brasse , or siluer , for a meridian or right circle , as is vsed to be done in the placing of all globes in their frame or foote , whereon may be made diuerse situations of needles , and descriptions Magneticall , as Tab. IIII. Fig. 1.

Tab: IIII diagrams

The better to vnderstand this foresaid demonstration , I would wish you to haue in readinesse a little directory-needle , with a foote flat and round , and a pinne in the center of it , to carry the needle , as in the third type of this IIII. Table . Let this circular foote be deuided into foure parts and quadrants , with lines crossing each other at right angles in the center ● , where the pin that carieth the needles , and at the beginning of euery quadrant set these figures , at the first 1 , at the second 2 , the third 3 , and the fourth 4 , now in the limbe , free from all needles , set downe this needle with his foote at the aequator d , and the needle will seate it selfe paralell to the axis of the Magnet a b , then turne the foote of the needle about , that the diamiter of the figures 1 , 3 , may be directly vnder the needle , thus in this syte carry the foote and this diamiter of the needle alwayes paralell to the axis of the Magnet , and place it in m , where it will point ouer the figure 2 , the beginning of the second quadrant hauing finished one quadrant of circumuolution about the foote or epicicle , then carry this foot with the needle with this diamiter paralell to the axis , as before , and place it against a the pole , and the needle will point to 3 the figure of the foote : hauing finished halfe the epicicle of his foote , then remoue the foote with the diamiter 1 , 3 , paralell to the axis of the Magnet , and rest it at o in the rimme , and the needle will point at 4 , hauing perambulated three quadrants , and then rest him at the aequator c , where he will point to the figure of 1 , againe , hauing finished a whole epicicle about his foote , in this iourney about halfe the Magnet : so likewise if the needle be transported beyond the aequator to trauell by the other pole b , to finish another epicicle , the point of the needle , that is of affinity with this iurisdiction , will offer his seruice , whereto place the figure of 1 , to stand iust vnder him at the aequator e , which here likewise will be situated paralell to the axis of the Magnet , and the foote being in this sort aequidistant-wise to the axis conueyed in the limbe to p , the pole b to n , and lastly to the aequator d , againe the needle in this hemisphericall part of the body of the Magnet will describe another epicicle about the foot that carieth him , so that it is most apparent that the needle in his circūambulation about the Magnet , doth turne himselfe twise about , and make two whole circles , or epicicles in this voyage , as hath bene demonstrated .

Whereas the needle in his progresse from d the aequator to m is but almost 34 degrees from the same , in which space he maketh his first quadrant , but the way from m to the pole a , is almost twise as large , in which he maketh another quadrant , it is necessary that this circumuolution of the needle from the aequator d to m not 34 degrees , should be much more sudden and swift , being in so little a space of the quadrant d a , then that forming of a quadrant by the needle vpon the epicicle of his foote when he passeth from m to the pole a , being a space almost as large againe , and therefore the mouing of the needle in making the second quadrant of his foote , should be almost twise as slow as the finishing of the first quadrant , if like time be allotted to both their passages . I thought good to set this needle and foote in the III. figure , vpon the limbe in the next Tab. V. which will serue also for the demonstration in the chapter following .

Yet it may be noted to the contrary hereof , the case being altered , that if there were a cutting away made of part of the paralels about the pole , and that the pole were made flat and plaine , as it hath bene shewed Tab. III. Fig. 11. that then the application of the needle at right angles , to the axis , at the angle and edge of the Magnet , being the most protuberant place , and the needle would describe but one quadrant from the aequator to this angle , and the other quadrant of the needles conuersion , betweene this angle and the pole , would be on the flatted end ; and then in this truncated body , the motion from the aequator to the angle , for the first quadrant would be very slow , and the motion for the second quadrant would proue far swifter .

Now for Magneticall attraction and apprehension , it is to be obserued , that at the poles the Loadstone doth attract and retaine Magneticall bodies perpendicularly and most strongly , and at other places most weakly and obliquely , and neerer the pole more strongly . But where the poles be flatted , as is sayd , and the application at right angles , there the erection of waights is altogether as strong as at the poles , taking vp in paralell-sort vnto the axis of the Load-stone by two teeth , and at right angles by one tooth .

Lastly , for the vse of the application of the Inclinatory-needle , I haue set downe a second figure , and in the margent haue delineated out in pricked lines , what application the needle hath , and maketh in euery tenth degree of the quadrant , from the aequator to the pole in the limbe of the quadrant C B , as likewise in the quadrant D A , there is set forth how the small wier and short erecteth it selfe in euery tenth degree in that quadrant , a thing hereafter more plainely demonstrated by a diagramme in the XXXVI . chapter , by calculation , and by ring , but indeed the matter will be more naturally and truely demonstrated in the chapter following .

CHAP. XIII .

Of one circle the Needle maketh round about the Magnet .

EVen as in a semicircle if sights be applied Euc. 3. Prop. 2 ● to the diamiter , and a plim line fastened to one end of the diamiter , this semicircle will serue onely for the vse of one quadrant , though it haue two quadrants contained in it , so this Chapter will abreuiate the motion of the needle in the former Chapter , as the quadrant doth the semicircle that in the former Chapter described two circles about the Magnet , and shew a way and deuice how the needle , being alwayes caried about the Magnet , shall make but one circomuolution about the circle of his foote , although before he made two circles about it , and this demonstration is of most necessary vse for to find out the angles of the Inclinatory-needle , with the axis of the Earth in euery eleuation of the pole , and what they are from the Horizon , and knowing what number of degrees they include in any place , the altitude of the pole in the same place shall be accordingly knowne .

Tab● . ● diagram

In the Terrella or Semiterrella let the poles be A for the North , and B for the South , and the aequator C D , part the semicircle A D B into two quadrants at D , then make other semicircles in the verge without A D B for the degrees and figures in each quadrant , as is vsed to be done in other quadrants , then deuide each quadrant , and euery one of these into three other parts , then deuide these parts into smaller parts , and if the circle be bigge inough , deuide these last into fiue parts a peece , and thus haue you either quadrant deuided into ninety parts , then set the vsuall numbers of tens at euery tenth part to ninety , ending at D , as in this type , Tab. V. Fig. I.

Then about a quarter of an inch aboue c in the verge , draw a line at I , at right angles to C D , and from I as a center describe vpward a semicircle to touch that line F I G , deuide this semicircle into two parts and quadrants at H , ioyning I H together in one line , after draw other semicircles within the semicircle F H G for the degrees and other numbers , as you did in the former quadrants , then diuide each of these quadrants into 90 parts , beginning the diuisions at F G , and ending at 90 in H , then set the figures at euery tenth degree , as is vsed to be done . Lastly , vpon this center I , place the Magneticall needle vpon his pin , Tab. II. Fig. 20 , that is , the needle that is thicke and short , hauing at the one end an hole drilled , for to receiue a wier of brasse or siluer , to counterpoyse the thicke head of the needle , and to reach vnto the farthiest circle of the deuisions of the two quadrants of this semicircle : this needle and semicircle would be couered with some glasse and slude , as dials vse to be couered , for a little aire and the breath of your mouth , when you looke neere to see what deuisions the taile of the needle cutteth , will moue the needle and driue it away .

This limbe and verge thus furnished with these two semicircles , and this needle being placed about the Terrella or Semiterrella , so as it may very easily without any great force be turned about ; in this situation of the needle , as it is in the type , the needle seeth it selfe at the aequator C , paralell to the axis of the stone A B ; we will call the inner semicircle of the limbe A D B , that is next to the Terrella or Semiterrella , the meridian circle of the altitude of the pole ; the outward externall semicircle F H G , we will terme the meridian Inclinatory semicircle , because the needle Inclinatory doth shew in these quadrants certaine parts and degrees , answerable to euery degree of the eleuation of the pole , of the Terrella , or Semiterrella , declared in the inner quadrants of altitudes of the pole .

For practise hereof , if it be desired to know where the pole is eleuated ten degrees aboue the Horizon , what degrees the Inclinatory-needle will point at in the Inclinatory meridian semicircle answerable thereunto . Here turne about the limbe and verge , vntill ten degrees of the semicircle of altitude be placed iust with the pole A , the pole being eleuated so many degrees aboue the Horizon , then looke in the quadrant of the meridian inclinatory semicircle , and his needle will point to 20 degrees , the very true parts , the Inclinatory-needle being placed in his ring and meridian circle , hereafter to be described , will point at in trauelling where the pole is eleuated ten degrees , after this manner seeke out what will be correspondent where the latitude of the pole shall be 20 or 30 degrees , and this needle will point out the correspondent degrees of the angle of inclination in the meridian-inclinatory semicircle , to these or any eleuation that shal be desired .

Therefore here you see how profitable , and of what great vse this demonstration is , in helping to attaine to the reason & true knowledge of the Inclinatory-needle , which placed in his ring , and caried about the earth in the meridian , doth only shew his angle and inclination to the axis , but this demonstration directeth from the stone it selfe what will be the number of degrees that the angle of the inclination maketh aboue the horizon , and what degree of the eleuation of the pole wil be answerable thereto , and from hence Tables may be made and collected what degrees of the Inclinatory-needle wil be answerable to euery eleuation of the pole .

CHAP. XIIII .

Of the distance and Orbe of the Magnets vertue .

Tab. VI diagram

Place wiers , about an inch in length , within their length in the orbe of a good Magnet , and they will skip vnto the Magnet , as though they were quicke , and will vnite and adhere fast vnto it , vntill they be taken off .

The celerity of motions , attractions , and conformities within the Magneticall orbe is according to the goodnesse of the Loadstone , the greatnesse of his bulke , conueniency of his figure and smoothnesse , and in the shortnesse of the distance in the aire , or in water ; yet further then in these the Loadstone extendeth his vertue by contaction and continuation in a long wier set vnto his pole , which wier will moue a needle , or adhere to another wier at the end of his length ; but this is done by augmentation of the Loadstones vigor , as shall be declared .

Although that such substances , which be not Magneticall , be placed betweene the needle and Loadstone , yet they cannot hinder the orbe and proceeding of the Magneticall vigor , as if a Loadstone should be inclosed in a boxe of wood , stone , tinne , siluer , or brasse , yet the Loadstone will extend his Magneticall orbe , wherein many pretty and ingenious Magneticall practises may be wrought admirable to behold , as hauing the formes and protractors of creeping things , beasts , footmen , horsemen , and flies drawne in past-boord , hauing but a short wier closely conueyed into them , and placed vpon a trencher , paper , or plate , shall be caused to moue , stirre , passe on , and flicker , as though they were aliue , onely by mouing the pole of a good Magnet directly vnder them .

Also if a Magnet be fastened in the roofe , or ouer a doore , it will hold an iron waight in the aire , Tab. VI. Fig. 2. that hath a thred fastened to it to hold it short that it be not drawne close for to be vnited vnto the Load-stone .

Likewise if a short peece of iron , or cap , be held within an inch of a strong Magnet stone , Tab. VI. Fi. 3. it will take vp great waights in this orbe , though not so much , as if it touched the stone and pole : but if the cap be held ouer the pole , it will hold a waight vp rather then the pole , Tab. VI. Fig. 6. I hold it needlesse to demonstrate how all the needles of dials , Magneticall instruments , the Marriners compas , and inclinatoryring do all of them moue within the orbe of the Magneticall vigor of the earth , onely I will shew you a prety practise or two for delight . Get a wier of foure or fiue inches in length , and thrust it through a corke , then it being touched with the Loadstone , place it in a basen of water , and it will moue and direct it selfe North and South , by the vigorous orbe of the earth , Tab. VI. Fig. 4. and also incline and conforme a conuenient angle with the Horizon and axis of the earth . This practise is profitable for trauellers , who hauing sowing needles touched , may pricke them vpon any peece of wood , and place them in the water , and it will set out the North and South insteed of a compasse : but if for pleasure-sake you take another wier , thrust through a round corke , and let his vpper end be touched at the contrary pole , and placed in the bason of water , these two after some time will take knowledge of each other , and will begin to moue and stirre , and draw neerer and neerer together , Tab. VI. Fig. 5. and comming neere , will moue the faster , and suddenly ioyne together at the vpper ends , on these wiers paper-tilters on hors-backe might be fastened , and they would runne their course together vpon corkes in the water , &c.

CHAP. XV.

Of Applications .

Tab VII diagram

Take a long Magnet that hath the poles in the middest , Tab. VII . Fig. 1. as A B and the aequator C D , the needles placed in the middest , apply directly vpon the axis , and at the ends , and at the other places obliquely . The second stone is a long Magnet , that hath his poles A B in the ends , and the aequator C D in the middest , Tab. VII . Fig. 2. here the needle against the aequator standeth at right angles vnto it , and paralell vnto the axis , but at the either end of the Loadstone the needles apply themselues at right angles to the axis , and paralell to the aequator , and in the intermiddle spaces the needles apply obliquely to the Magnet .

Now I would haue you to prouide two long Loadstones , that haue the poles in the middest , like that Tab. VII . Fi. 1. and before him place three Magneticall needles , two at the ends , and one against the middest , or pole , as in Tab. VIII . Fig. 1. the middle needle will behold the pole , and the other will apply obliquely , as before in Table VII . Fig. 1. now bring neere the second Loadstone , that hath his poles in the middest , and place B the South-pole toward the needles that behold the South-pole B of the first stone , and these needles will , betweene these two South-poles , respect neither pole of these two stones , but seate themselues paralell to both stones , and make right angles with these two poles of one nature , as Tab. VIII . Fig. 1.

Now take away one of these stones , and after turne the North-pole A , towards the needles that behold the South-pole B of the other stone , and they will all of them situate themselues equidistant-wise , and at right angles to the aequators of both stones , as Table VIII . Fig. 2.

Tab: VIII diagram

Moreouer , take other two Magnets that are long , with the poles in the ends , like that Tab. VII . Fig. 2. and lay it before you , and place three needles before it , two at the end , & one in the midst against the aequator , which will apply paralell to the axis of the stone , and those two at the ends will seate themselues at right angles to the axis , as before ; then set the other long Magnet that hath his poles in the ends with the North pole A , against the North-pole A of the first stone , Tab. VIII . Fig. 3. and all the three needles will apply themselues in a straight line paralell to the axis , somewhat like the order of the first type , yet contrariwise .

Now take away this second stone , with the poles in the ends , & turne it , and place the South end B , against the North end A , as Tab. VIII . Fig. 4. and then the 3 needles will stand at right angles to the axis , and paralell one vnto another , and to the aequator .

This is to be obserued in these applications , that the neerer the second Loadstone is placed to the needles , in aspect with the first Magnet , the better will they shape out these figures of applications , & in the approching they will vary , by little and little , from their first situation , vntill the vertue of the two Loadstones be equall in their orbe .

It may be imagined that these applications , for the most part , should be found naturally vpon the earth in trauelling or nauigating betweene two great Ilands or high Magneticall continents , but the first & fourth figure of this eighth Table cannot be found naturally in any place , Tab. VIII . Fig. 1. and Fig. 4.

There is also much variety of variation in one needle neere two Magnets , or a Magnet and Magneticall body , as place a needle on a little foote vpon the Terrella , Semiterrella , or Loadstone , and it will direct it selfe rightly vpon the meridian of the stone , as hath bene proued before , Tab. III. Fig. 9. but if you hold a little peece of iron toward the point of the needle , the point will flie from the iron , and deflect from his meridian a little . Yet let this peece of iron touch the Load-stone and be vnited vnto it , and put it towards the needle a farre off , and the needle will turne from his meridian , and decline and vary towards it , the contrary is to be sayd , if this iron be put towards the taile of the needle .

Now take two long Magnets , that haue their poles in the end , and place a needle before the aequator of one of them , and it will apply paralell to the axis , then bring the other Loadstone , and place the end where the pole is against the aequator of the first Loadstone , as Ta. VIII . Fig. 5. and then the needle will vary his position , and seate it selfe at right angles , to the axis of both Magnets .

So also take two Loadstones , and let one of them haue the poles in the middest , and the other in the ends , and you shall behold much artificiall variety of the application of one needle vnto them . Place a needle before the middest of the Loadstone , that hath his poles in the middest , and it will behold the pole : after lay downe the other Magnet , that hath his poles in the ends , and set his aequator against the needle , and it will vary his position , and stand paralell to the aequator of the former Magnet , whose pole he beheld before , as Table VIII . Fig. 6.

Tab. IX diagram

Set a needle against the end of the Load-stone , that hath his poles in the ends , and it will rest it selfe at right angles to the axis , then apply the second Magnet to the needle that hath his poles in the middest , Tab. IX . Fig. 2. and the situation of the needle will be altered to be paralell to the axis he beheld at right angles at first .

Place at the corner of that stone that hath the pole B in the middest , a needle , and it will apply obliquely , then lay the end of the other Loadstone that hath the pole A in the end , and the needle will apply at right angles to the axis of both the stones , as it is Table IX . Figure 3.

But set a needle afore the end of the stone that hath his pole B in the middest , and set the end of the other Magnet that hath in the end the pole B of the same denomination , as Tab. X. Fi. 1. and the needle will apply , as is to be seene in the type in a straight line to the last , and paralell to the axis of the first .

Also apply the aequator of this second stone , that hath the poles in the endes vnto the needle , placed as afore , vnto the first stone , Table X. Figure 2. and the needle will be paralell to both axis , let the needle stand against the corner of the first stone obliquely , and apply the end of the second stone with the pole in it , Tab. X. Fig. 3. and the needle will apply , as in the Tab. IX . Fig. 3.

Tab X diagram

CHAP. XVI .

Of preseruing the vertue of Magnets .

HAuing treated of the parts of the Magneticall bodies , of their motions , and applications , now we will speake of his other naturall vertues and properties . Some haue thought it very conuenient to keepe the Loadstones in filings of steele and iron , to preserue their vertue and vigor , thinking that the Magnet is fed , or , at least , very much refreshed with them , because they will cleaue so fast to the sides neere the pole ; But I do not allow this way so good to preserue them , rather I like the keeping of them in a bag , or cloute of woollin-cloth , close from the iniury of the heate and cold of the weather , or in a case or boxe fit for them , and it is very necessary to wipe them often from dust and grease , and to haue a care that they do not rust .

Also it is very commodious and naturall for them that they be layde vp , and placed according to that naturall situation the which they would affect and respect , if they were caried in a place and fashion free from renitency and resistance in the aire or water ; therefore they would be laide vp , or hung accordingly as their poles and pointes do particularly respect , to the North and South , which will comfort them exceedingly .

Besides , if the Loadstone be sometimes polished , it will strengthen and releeue the body of the Magnet very much . If a weake Magnet be rubbed at one of his poles with a stronger Loadstone , he will be bettered by it in his vigor and vertue , if not augmented therein .

Set a Magnet of no force or strength , that can easily be perceiued , vpon a Loadstone of good strength and vigor , especially vpon his poles , and he will shew a vigor , as if he were as strong as the Loadstone is , whereunto he is vnited , but after that he is taken away , he will be as weake as before , vnlesse it be often done .

CHAP. XVII

Of contributing the vertue Magneticall to Iron or Steele .

THe iron barres in windowes , being there placed North and South , do receiue a polar vertue , and directory faculty in time from the vigour of the orbe of the Magneticall globe of the earth , and hauing marked them with notes to know which end was South , & which North in the window , take them out and tye a thrid about the middest of them , that they may hang leuelly in the aire , and the end with the South note will turne it selfe into the North , and the other note will behold the South , contrary to their place in the window , where they were first animated Magnetically .

Likewise , if a long peece of iron be forged North and South , and laide by to coole in the same situation , he will be animated and indewed with a polar vertue , and moue in the aire , being hung in a thrid , or put in a boate on the water , and turne to the contrary pole to that from which he first receiued the Magneticall vigour .

If a rod of iron , a wier , or directory-needle , be ouer-heat in the fire , so that they haue lost all Magneticall vigor to direct them North or South , yet let them be touched with the Loadstone at one end only , and they will be excited with a directory and polar vigour at both ends , and the one end of the semidiamiter will be of the North , and the other of the South prouince and nature , and being placed according to Magneticall orders , will direct their points to the North & South , contrary to the pole that animated them with this vertue polar .

Also take rods of iron , wiers , and Magneticall needles , that haue neuer bin touched with the Load-stone , and rub them vpon the poles , caps , or teeth of the Loadstone at the ends , and they will be much refreshed , vigorated , and animated with the polar and directory vertue at both ends , both of the North and South-poles , as though they had a new life of quicknesse infused into them , and these shall refresh other needles that shall be touched with them , and apprehend and draw them away like captiues , and will not let them loose from them , vnlesse by force you seuer them .

The best way to touch , incite , and giue the polar directory and Magneticall vigour and faculty vnto needles & Marriners compasses , is to rub them from the middest of the needle where the aequator of their axis is vnto their points vpon the pole , cap , or tooth of the Loadstone , drawing them thus from their middle to the ends , vpon the cap , pole , or paralell neere the same , vnto the axis , or at right angles to it , them after draw the other end vpon the other pole , cap , or tooth , diuerse times , as afore , and these needles , wiers , and plates for compasses , shall be perfectly touched and vigorated .

In long Loadstones that haue the poles in the ends , if a wier be drawne paralell to the axis , from the poles end to the aequator , it will be incited with that pole .

It is doubted whether the touch and polar vertue wil be giuen as wel from a paralell some distance from the pole , as from the pole it selfe , it is plaine , that from those paralels and parts , neere adioyning to the pole , the greatest vigour of politie Magneticall doth proceed , yet in paralels , neerer the aequator , it will be giuen likewise , & the vertue directory will be very sufficient .

If you touch the needle amongst the paralels , it is the best way to rub the needles alongst the meridians towards the pole , rather then to rub the crosse the meridians , in a paralell manner , yet this way will giue the polar and Magneticall vertue also .

Some haue thought it better to touch compasses , and Magneticall needles , rather on the Loadstone then vpon their caps , thinking that the vigor and faculty Magneticall will continue longest that is giuen from the bare Magnet stone , the truth is to be obserued in time . Yet the cap and tooth giueth and imparteth a stronger vigour to the needles then the bare stone doth , because the vertue of the Loadstone is increased as much by the armor and cap as if his bulke simply were tripled .

Needles and wiers of steele , heated to an height , and reduced backe to a blewish colour , will receiue a stronger touch , and retaine it ten times longer then iron will , howsoeuer he be hardned , yet iron is best for caps placed neere the stone .

That end of the needle , whether directory or inclinatory , which is to be touched , ought to be somewhat lighter then the other , especially for the North , and most vigorous touch end of the stone , because that the touching will sway downe a little , and the needle hath two motions , one of direction , the other of inclination , and then the needles and compasses will play more leuell and aequidistant to the horizon for the sayd vses .

When any Magneticall needle or wier is touched from the North-pole , or tooth of the Adamant , that end of the needle will respect the North-pole of the Magnet , but being seuered out of the orbe of the Adamant , it will be directed into the South by the Magneticall vertue of the earth .

But if a round globe or ring of iron be touched with the North-pole of the stone , the place touched will haue the vertue of the South-pole , & the North-pole will be in the opposit part , and being seuered from the Magnet , it will not turne to the contrary part , as it falleth out in long Magneticall needles & compasses , as before .

If a ring of iron be touched , the correspondent pole will be in the opposite part , but if this ring be cut asunder , and made a straight wier , then both ends will haue the vigor of one pole onely .

Excite a directory needle at both ends from one pole , and they will both be of one nature , and looke what point was last touched , and that will turne , as if he onely were touched , and direct more surely , with lesse wauering too and fro , then the other touchings will , spoken of before .

Let a long peece of clay newly burnt , coole North and South , and it will receiue power Magneticall from the earth .

Set two Loadstones with their poles of one denomination , at the ends of a peece of clay whilest it cooleth , and both ends will be of one nature .

If a long wier be touched in the middest by the Loadstone , and passed through a corke , and set for to swim in the water , it will wauer vp and downe vncertainely , as though it were not touched : but if it chance to rest it selfe towards the pole , in time it will be indewed with his vertue .

Set a peece of iron vpon a Loadstone , as you did a weake Magnet in the end of the former chapter , and it wil haue a great force , but take it away from the stone , and almost all the vigor will be departed .

CHAP. XVIII .

Of augmenting the vertue of the Magnet .

THere is a meanes found out whereby the Load-stones that will take and lift vp a very small waight , may by being armed with a corselet and teeth , be enabled to take vp more ounces with his armor , then he could , being naked and vnarmed , lift vp scruples and graines .

The first way is by fashioning caps of iron or steele to either pole , as hath bene described , Tab. I. in the second Chapter , whereby the Magnet will lift vp a great weight of Iron at one end perpendicularly to the axis , and after , if you turne the other end to the weight , it will by his force lift vp the same weight also , if the stone be good and of equall substance and fashion .

This way or arming is most vsuall , for those Loadstones that be of a long ouall forme where at the poles there is fitted and placed two concaue peeces of steele , which are fastned and held close to the same by three or foure long narrow plates of siluer or brasse , not vnlike to that order which is vsed in tipping of cuppes with siluer , that be of Ostridge-egges , Indian-Nuts , Mace-wood , and Stone , which from the bottome to the verges and edging , haue siluer plates for to hold the edging and bottome together : some trimme their Load-stones all ouer with siluer , and guild both the siluer and the armour , ioyning altogether with pretty ioynts , as in a case to open and shut .

There is another way of capping and arming of Load-stones when they haue a side parallell to the axis , made straight , plaine , and flat , and the pole rounded or flatted in the end , such as are the Semiterrella , or halfe ouall forme . Tab. I. Fig. 2. 4. and of many angles , as in the types of the first Table , all these formes may haue their armour on the ends , where the poles are of such breadth , as shall be comely , but the larger they are , the better it is , and from these cappes to haue two square formes of Steele or Iron , like vnto teeth , a little descending lower then the bottome of the stone , of bignsse and length , as the bulke of the Magnet shall permit , these teeth because that they do descend at right angles from the poles , will iointly take vp great weights , Tab. XI . Fi. 12. 13. parrally to the axis of the Magnet , and yet at one of the teeth Tab. XI . Fig. 11. will lift vp as much as any cap doth directly , and in one axis from the pole , the weights for this forme , ought to haue the heads of their weightes , like an headlesse crosse , as is described , Tab. II. Fig. 2. 3. 4. Heere obserue what weight one of these teeth will eleuate ●n the aire , for both teeth ioyntly lifting and holding one weight together , will take vp from the ground foure times as much in weight . There be some Magnets that will take vp with two teeth , sixe times as much as one tooth shall , and one I haue seene that will take vp twelue times as much with both teeth , as hee will do with one tooth , these teeth are to be fastened to the stone , with plates of siluer or brasse , by the skilfull workeman .

Such Magnets as be made plaine at both ends , hauing the axis in the middest of the stone , Tab. I. Fig. 5. 6. 12. may haue their armour with teeth on both sides , two teeth on the one side and two on the other , these will take and lift vp with like strength on both sides .

More-ouer , the vertue of the Load-stone may be further augmented , by increasing the number of teeth and shaping them so , as that they may take hold with foure or fiue teeth , as Tab. I. Fig. 7. and Tab. XII . Fig. 11. where the poles being in the ends of the stone , and haue had two teeth descending on either side , now the sides be turned , and these are also turned , in forme of a Greeke 〈◊〉〈◊〉〈◊〉〈◊〉〈◊〉 , and the stone hath his force multiplied and is made to take vp with foure teeth , hauing two teeth descending from either end where the poles are , which two teeth , are of one nature , and the other two of another ,

The other fashion for to take vp with fiue teeth , as it were a hand with fiue fingers , must haue the pole in the midst of the stone , which being made , the bottome must haue his cap , for this part , to haue three teeth , like a Slauonian 〈◊〉〈◊〉〈◊〉〈◊〉〈◊〉 , as Ta. XII . Fi. 12. and the other cap from the top must descend with two teeth like a Greeke 〈◊〉〈◊〉〈◊〉〈◊〉〈◊〉 , as in the type .

There is a way to cap the Loadstone , so that it shall take vp with eight teeth , vsing foure at one time , and foure at another , the stone would haue two broad sides where the poles are , and the teeth would bee in forme like a Romane X. or S. Andrewes crosse the center hereof would be placed on the pole , and the teeth artificially fastned .

If there bee two Load-stones that bee capped with their teeth descending from either end of like Diameter and length , then place those teeth together that be of a contrary nature , Tab. III. Fig. 12. and Tab. XII . Fig. 10. and they will vnite and adheare together , and if they continue thus some time , the weaker will lift vp a better weight .

CHAP. XIX .

Of the decay and decreasing of the Magnets vertue .

THe vigour of the Load-stone is much diminished by the euill keeping of it , as when it is laid in the open aire against the heat of the Sun , and subiected to cold , and all change of weather , or laid vp , as some do , in a boxe with rusty fylings of steele and yron , in a place neere a pan of char-cole to keepe it warme in winter .

There is nothing that hurteth the Load-stone more then the fire doth , for if the Load-stone be burnt in the fire it will leese all his Magnetical vertue and strength , the which may be a little restored by touching a good Magnet , and how weake so euer he be , he will be a conuenient Magneticall medium , to carry the extent of the Magneticall vigour to a farther orbe .

Aqua fortis will eate the Load-stone , and burne and mortefie him , as he doth eate into Iron .

The Magneticall Needle being touched and excited by the Load-stone will not pursue and point out the vaines of such Iron as be very stony and full of drosse , as not worthy the labour to be digged , because they haue little Magneticall matter and Iron in them , and if that part of the Myne of Iron be beate and stamped into powder , the Magnet will take vp very little of this dust , declaring the Myne to be nought , vnlesse the Myne be heat .

Crocus Martis wil not be attracted by the Load-stone , because his Magneticall vigour is cleane defaced and euaporated by the fire .

If a Magneticall Needle , lately touched and inuigorated by the Magnet , bee heated red hot in the fire , he will leese all his potency polare , and directiue faculty .

It is also conueient to vnderstand , that hauing touched and animated a Needle Magnetically , if contrary to this excited , the Needle be rubbed from the point to the middest vpon the pole of a Magnet , cap , or tooth ; so any long peece of Iron , or Steele else , as knife dagger , or sword , which before would haue attracted and lifted vp Magnetically , other Irons of some weight by being thus rubbed backe againe from the point to the middest , haue that vertue taken away , which they receiued before from the Load-stone , and are as void of all vertue attractiue , as they were before they touched the Magnet , so that they neither will adhere or lift vp the least weight , which was nothing to that they would haue done being excited .

If two Magneticall bodies be ioyned together at their poles , these two poles that touch together , haue the nature of the aequator , and will not then excite or hold a needle thus touching .

An Adamant doth loose much of his strength , if hee bee diminished , and haue any part of his body taken from him , especially if his figure was good before .

Some haue thought that certaine formes of the Magnet , which may be allowed for conuenient figures , do lessen the Magneticall vigour , chiefly in their attraction , as a sphericall or plaine superficies in the poles , of globes , and of square and angulous figures , but these full and obtuse superficies and flat formes at the poles do attract best with their cappes , and lift vp most , as hath bene declared in the eighteene chapter before , for this vigour proceedeth from the substance of the Adamant , better then in long and piked formes , which haue very little substance left about the poles , yet this assertion is partly true in such like formes of Iron , for in this mettle the long fashion is best .

A round plate of Iron to the pole , cap , or tooth of the Magnet , disperseth and diminisheth the direct extent of his vigour , like-wise a long plate , or square peece of Iron or Steele , Tab. II. Fig. 9. 17. applied to the two teeth of the Load-stone , doth deforme the figure of the body and depraue his vertue .

CHAP. XX.

Of the Commutation of the vertue Polar .

THe Polar vertue is said to be changed , when as the North-pole is made the South-pole , and the South-pole altered into the nature of the North-pole in Magneticall bodies ; this thing is effected , in a weake Magnet , by placing him a long time by a Magnet that is stronger , vnnaturally , which is done by adioyning the two North-poles , or the two South-poles of the two Load-stones together a long time , where the strong Magnet , will by his neighbour-hood take away that contrary nature of pollity that was in the weake Load-stone , and will make , and infuse into him that polar vertue , which doth naturally vnite vnto the pole of the strong Adamant , making that point and pole to be South which was North.

This thing is not onely experienced in two seuerall Magnets lodging together in one chamber and boxe , but also if you shall agglutinate and cement diuers Magnets of diuers strengths together , they will all of them be conioyned and vnited together , as if it were one stone and body , and may bee made and fashioned into a conuenient figure , and will be endued with one vigour Magneticall of one prouince , though separated they were of diuers polities and iurisdictions .

Magneticall needles and long formes of iron , as kniues , daggers , wiers , and such like , if at one time they be touched and excited with the North-pole , and made of his nature in all operations Magneticall , then another time let these North points be touched , as is vsed to be done with the South-pole of the Loadstone , this end now hath lost his former nature , and is made of affinitie and allegeance vnto the South-pole , and after if you shall bestow vpon him , by touching him againe at the other pole , the vertue of the North-pole againe , and then he will march vnder his banner , and looke by which pole he is last touched and relieued , he will remaine at his seruice alwayes after and beare his badge . Put clay of a long forme in the fire , after let him coole North and South , and it will receiue a polar vertue : after burne it againe in the fire , and let that end which cooled first North now coole South , and it will be commutated into the nature of the South , and the other North. Furthermore if a strong Loadstone be held somewhat neere such compasses and needles , as haue bene excited and touched with the vertue directory from the north by the Magnet , although they be in their boxes , yet the other end of the Loadstone will alter their situation , and the Lilly of the Compasses will be cleane turned , that that part and Lilly that should alwaies turne North , will either stand South , or else moue vp and downe vnperfectly , and weakly , hauing his first polar vertue changed for another , or else taken away .

This conclusion maketh many affraide to let two Magnets come too neere together , lest the one should rob the other , but this will not be effected presently in the Loadstones themselues , though that it be proued soone to come to passe in the Magneticall bodies of steele and iron .

If a directory-needle be excited at both ends from one pole , it will haue the vertue of that pole at both ends , but if both ends be rubbed backe from the points to the middest , on the same pole , both ends will haue the nature of the contrary pole , and if one end be passed from the point to the middest , that end will haue the nature of the contrary pole , and the other end will keepe his nature still .

CHAP. XXI .

Of the discord of the two Points of the Adamant .

THis Proposition is demonstrated by two Magnets swimming in their boates , in a bason of water , as Tab. XI . Fig. 5. 6. for if by force , their two North-poles or South-poles be placed together , they will abhorre the one the other , and part asunder by speedy flight .

Tab XI diagrams

When two Adamants shall confort , and keepe together , at their contrary poles , at the approching of a third Magnet they will be separated and flie asunder Tab. XI . Fig. 1. because that the pole of their Adamant , that is offered vnto them , is of the nature of the pole of one of the two Loadstones , which the stone of that denomination perceiuing , flyeth away from the company of the other , because two South-poles and two North-poles , in diuers Magnets , be at discord and war together , and cannot abide to dwell as neighbours together , but each of them , placed out of the others Orbe , will both aspect the North , with their North-poles , and the South with their South-poles , and thus two needles excited as Tab. XI . Fig. 2. will each of them , out of the others Orbe , haue respect to their propper pole , but if the needles bee within the Orbe one of the other as Tab. XI . Fig. 7. then they will moue and adhere together at their contrary poles , but if a third Needle be brought neere vnto them as Tab. XI . Fig. 8. then one of those Needles that did adhere , that had his pole of the same nature , with the pole of the needle that doth approach , doth cast about for to offer his other end of the contrary quality vnto it , and thus the first two Needles will aspect this third with their points of one denomination .

But this discord is not found betweene the Adamant , and the Magneticall Needles that bee excited and animated from one of his poles , for as long as the Needles bee within the view and orbe of the Adamants Magneticall orbe , so long they will behold and aspect him with a certaine dutifull conformity , application and respect vnto his axis , as it hath beene demonstrated in Globous & Angulous Magnets , but being seuered out of the Adamantine Orbe of the Loadstone , then they will flie , as from a foe , from that pole from whence they receiued their life and vigour Magneticall , and by the vertue of the earth conforme themselues to the contrary pole .

Contrariwise , take a large Globe or Ring of Iron , and touch them with the North-pole of the stone , and the animated place will haue the vertue of the South-pole , and adhere to the North-pole of the Magnet , and being seuered will keepe the same situation in the water , contrary to all Needles that turne the touched part to the contrary pole , as afore .

Set two short and slender wyars vpon the pole of a Magnet , Tab. XI . Fig. 3. and they will adhere at the lower end vnto the same , but whereas they should erect their other ends perpendicularly , those ends of the wyers will decline a great distance asunder , vnlesse by force they be vnited and ioyned together .

Contrariwise it will fall out if these two short wyers bee fastened to two seuerall thirds with wyer , and hanged ouer the pole , then neither of their ends will behold the pole , but for the hatred that the one beareth to the other , they beare off asunder in a great distance , desiring rather that their vpper ends , farthest from the , Loadstone should vnite , then that they should doe it .

Hold a knife to the Needle of a Dyall that is touched Magnetically , and the one point of the Needle will come to it and follow it , and if that the knife bee offered to the other end of the Needle it will flie away from the knife , so one end of any wyer , though vntouched , will attract the Needle at one of the ends , and driue the other end away , Hereof more hath bene written in the sixth Chapter . Some thinke that this quality of the poles , thus to flie off the one from the other , that it is no enmity , but proceedeth from a disponent vertue , to cause these Magneticall bodies to moue and turne away , to the end that they may better frame and dispose themselues to a conuenient and naturall vnition .

CHAP. XXII .

Of Magneticall Vnion .

MAgneticall union is when one Magneticall body naturally conformeth it selfe to vnite vnto any other Magneticall body , by conuenient angles & positions , that is , the South-pole of the one Magnet will apply and vnite vnto the North-pole of the other , as may be seene in Loadstones , carried in their boates vpon the water , and in Magneticall Needles and Wyers of Steele and Iron .

If two Magnets , or two Needles do vnite at conuenient points , a third Magnet or Directory Needle will first separate one of them till hee turne his contrary part , at the which hee will vnite with the third as Tab. XI . Fig. 1. 8.

There is a strong vnion , of body to body , and a weak , the strong coniunction is three manner of waies .

The first is commonly obserued to bee at the Poles , where one body Magneticall is conioyned and vnited vnto the other in a right line , vpon the axis at the pole Tab. XI . Fig. 10.

The second strong vnion falleth out when the superficies where the pole is placed is made plaine , where at the edges , Magneticall bodies adhere at right angles vnto the axis , as Tab. III. Fig. ●● . and Ta. VII . Fi. 2. but more plainely , this strong vnion appeareth when as the Adamant shall be capped with two teeth at either pole , descending at right angles vnto the axis , for here a tooth will lift vp as much perpendiculerly at right angles to the axis , as it will at the pole in a right line . Table XI . Figure 10. 11.

The third strong vnion , and strongest , is when at a Meridian in the Loadstone there is a superficies made flat and plaine , paralell vnto the axis , where the coition according to the conformity in the aequator , inclining neither to one pole , nor to the other , is most strong , for whereas wyers and weights , at the pole , hang and adhere vnto it , but by one end onely , heere they will adhere alongst their axis , leaping more violently to adhere with their whole side and vnite , then they will from their endes vnto the poles , as Tab. III. Fig. 4. therefore the Adamant being armed artificially with two teeth , at right angles vnto the axis , will in this paralel-conformity vnto the axis , apprehend and lift vp weights heauier by many times , then the caps at the poles will , Tab. XI . Fig. 12. because these receiue their vigour from the forces sent out of both Prouinces of the Magnet .

The weaker vnition of Magneticall bodies together is in the other parts of the Meridians , where the conformity and applications of their bodies is oblique to the axis , though that neere the pole , the oblique coition is stronger then it is by the aequator , Notwistanding , there is an oblique coition , as strong as the strongest vnion , and will take vp as great weights , as the paralell vnition to the axis doth , and this is , as it were , a paralell coition also betweene the teeth and the head of the weight , yet oblique to the axis of the body of the Magnet , as Tab. XI . Fig. 13. hauing his supplies of strength from all the Magneticall body of the stone .

Vnition also , is either naturall , halfe violent , or else depraued ; the naturall coition is when the vnion and conioyning of Magneticall bodies is by the contrary parts , as in Adamants , by the poles North to South , and in needles by head and taile , as Tab. XI . Fig. 7. Tab. XII . Fig. 5. 6. 9. so two wyers swimming on their corkes in the water , being touched by contrary poles , will march and hasten to salute one the other , like two louers , Tab. VI. Fig. 5. Likewise in Adamants that be armed with two teeth , it falleth out that they will embrace the one the other , onely with the teeth and parts that be of contrary prouinces , and not with those of like nature and prouince . Tab. III. Fig. 12. Tab. XII . Figure 10.

Tab ▪ XII diagrams

Now that vnition , which Magneticall needles touched and excited at the pole of the Adamant haue , may bee thought to bee halfe violent and some-what strange , Tab. III. Fig. 1. 6. 7. Tab. IIII. Fig. 1. because that heere there is an affinity of two Magneticall bodies of the same nature and denomination , and not of the contrary , that it seemeth that the Magneticall nature , betweene the Adamant and the Iron , is both very different from all other Magneticall bodies and some-what imperiall ; for it is not to be seene either in Magnets one towards the other , though they be of the same rocke and peece , or in any wyers of yron or steele of one towards the other , or in the earth it selfe , with those that she doth Magnetically animate , that that pole which is excited , or animated with a pole of the same nature , should respect and conforme it selfe , being artificially , without renitency , carried vnto a pole of the same nature and denomination , from whence he receiued his first vigour .

Here therefore , no doubt , the Adamant is Masculine vnto his beloued the Iron and Steele , and these are Femenine , as more apt to obey , respect , and follow the Masculine , subiect to be attracted by him , whose presence quickeneth , reuiueth , and animateth them in all kind of vigor and commutation .

Thirdly , when yron is vntouched , and vnexcited , the coition is the weaker , but when a small peece of Iron shall be in a boate , with materials of other lading to be vnited to a Magnet in his vessell , heere the coition is depraued and weake , because the Magnet affecteth and draweth his owne beloued best , when she is not laden or mixed with materials that be of different nature not Magneticall , and for this cause the Adamant will take vp a greater weight , all of Iron or steele , then when a great weight of other subance , is fashioned to a small weight of iron or steele .

The greatnesse of the bulke of the Adamant helpeth vnition , so doth the length of the axis , and vertue disponent to set the Magneticall bodies in conuenient situation .

Besides , there is a vertue attractiue , besides the disponent vertue , and a directiue and inclinatory faculty in the Adamants , that bring Magneticall bodies to vnition and apprehension , the two first retaine them in vnion and coniunction , proceeding especially from the goodnesse of the stone , the latter two helpe the disponent vertue , and are to be found in all Loadstones , and in the earth it selfe .

CHAP. XXIII .

Of attraction Magneticall .

MAgneticall attraction is a naturall incitation and disposition conforming to contiguity and vnion of one Magneticall body vnto another , and no violent haling of the weaker to the stronger , being an appetite of vnity proceeding from both bodies that are separated , as two Magnets floating in their boates do not at first run together , as it were , from center to center of the bulke vpon a violent disposition or attraction , but the disponent vertue first worketh , then the allicient and Adamantiue vertue in them , both for vnition , doth shew his vigor to ioyne them by conuenient termes the one body vnto the other , Tab. XI . Fig. 5. 6.

Also the Adamant doth more strongly attract iron , hauing a more Masculine nature to attract her , and inableth her , bestowing vpon the iron , that he toucheth , a great quantity of his strength without any losse vnto himselfe , so that shee hath power to attract other iron strongly , which before the excitation from the Magnet shee could not doe , and therefore excited formes of iron and steele , are quicklier attracted , then such as are not touched , because they haue more Magneticall vigour in them .

Such Magnets as be armed with iron , attract more strongly then the bare stones doe , because that hereby their vigour is increased , being more strong , and extendeth it selfe further , as if a long iron wyer bee conioyned to the pole , or tooth of a Loadstone , and to the end of this , lay to another , and at the end of that a third , and so forward , the Adamant will hold them all , or most of them , according to his vigour and strength , Tab. XII . Fig. 1. all touching one the other , and cleauing together , as linked in a chaine .

Place a wyer some-what short vpon a Load-stone neere the pole , or further off , and hold an iron or Magneticall body towards it , and the wyer will rather bee attracted away by this weaker body , and leaue this strong Magnet , Tab. VI. Fig. 6. and before the yron touch it , it will decline and bend towards the yron that approcheth , so will needles directory deflect awry , being placed vpon the Magnet , from their conformity to any vntouched wyer , and be attracted by them , and this proueth , that the eminent parts of the earth being Magneticall , may attract the Compasse to vary from the true Meridian of the earth .

The naturall attraction of Magneticall bodies , is that the North-pole do attract the South-pole , and the South-pole the North , although betweene the Adamant and the iron there is that sociability , that the North-poles loue one and the same pole .

CHAP. XXIIII .

Of the strong apprehension of Magnets

THe apprehension of Magneticall bodies is a strong vnion , cleauing and sticking of them together , that they will hardly be seuered , being strongly retained by the vertue and loue Magneticall , as though they were tied , glued , and soudred together , this coniunction and agglutination is performed by certaine conuenient positions , whereof I haue spoken in the XXII . chapter of vnion ; according hereunto if two Magnets be swimming in their boates vpon the water , within the orbe and vigor Magneticall one of the other , they will moue to conioyne and be grappled together like two ships , and if one of the vessels be halled , the other will follow , Tab. XI . Fig. 5. 6.

A strong Magnet will hold but a very small Magnet at the poles , hauing the North-pole applied to the South-pole , for to lift the small Magnet in the aire , but offer a wier of pollished iron or steele , that is a good deale heauier then the fragment of the Magnet was , and the Loadstone will lift this up from the ground and retaine it firmely , Tab. XII . Fig. 5.

If Magnets be of one mine , the biggest will lift vp and hold the greater waight , for this purpose the longer forme from pole to pole is best , and bulke being compared with bulke , this forme will take vp the greater waight , because his diamiter is longest .

Take a long peece of iron or steele , as a knife , or dagger , or sword , that is finely polished , and touch and excite them Magnetically , and these shall take vp a greater waight of iron then the Adamant it selfe , so it be very good and little shall , that gaue them their vigor Magneticall to lift vp , and retaine firmely , Table XII . Fig. 2.

I haue a Loadstone that will vigorate a sword to take vp and hold a pound waight . Likewise Magneticall needles and excited wiers will strongly retaine and adhere one vnto the other at their conuenient poles , hale one the other , and lift them vp , and retaine them firmely , for such Magneticall formes of iron and steele as be touched and animated Magnetically , are sooner apprehended , held fast , and lift vp in the ayre then those that be vntouched and vnexcited , because that when the Magneticall vigour is infused , dispersed and spread through all the parts of the iron-waights , or of steele , these formes are sooner vnited and faster tied , as it were , with strong ligaments and cords , both vnto the Load-stone , or one vnto the other , Tab , XII . Fig. 3. therefore if sand or other matter that is not Magneticall be fastened and bound vnto a smal peece of iron , or this small peece of iron be fastned to a paire of seales , that haue strings to the scales , though iron be the waights of the scales : yet the Magnet will lift vp and hold a greater waight that is all continued iron , then he will do of these mixture and intermission of Magneticall medium , of diuerse and different substances , not Magneticall .

If a Magnet be fastened to the pole of another Loadstone by his conuenient vpper pole then a greater waight then before will be apprehended by the Loadstone and taken vp , because that the Load-stones , vertue is increased and augmented by the addition and adioyning of the other Magnet , Ta. XII . Fi. 6. 9. Euen so , for the same cause , if a wedge of iron be placed on the vpper pole of a Load-stone , the other pole that is downward will take vp a greater waight , Tab. III. Fig. 2.

If there be a thin plate of steele or iron held or fastened vnto the nether pole of the Adamant , betweene the Loadstone and the waight , then the Magnet will lift double , and sometimes decuple , or ten times as much againe , from this practise begun and grew the arming and capping of Adamants with steele and iron , after diuerse manners , Tab. II. and as hath bene declared in XVIII . Chapter , Of the augmenting the vertue of the Load-stone ; by this arming of the Loadstones with steele and iron in conuenient places , their vertue and potency is greatly multiplied , both to vnite , attract , apprehend , and lift vp greater waights , and also to moue , turne , and conforme Magneticall needles a far off , and the needles by hauing a strong vigour infused into them direct and retaine themselues more firmely in their conformitie and direction Magneticall .

If a plate or cap of iron be held to any paralell betweene the aequator and the pole , crossing in any meridian , there will be an apprehension and retention of iron , wiers , and waights , much heauier then the bare vnarmed stone wil hold without this cap , Ta. XII . F. 7.

Where the superficies of the Magnet about the pole is flatted and made plaine , hauing armour applied to it , and a tooth descending from the point at right angles to the axis , here this tooth will take vp and lift as much as the cap at the pole will , Tab. XI . Fig. 10. 11.

Those Adamants that be capped to take , apprehend and lift vp at the pole onely , if there be three of them readily prouided , put the second to the nether pole of the first , and he will retaine him firmely , then adde the third to the nether pole of the second and the first , by vertue infused into the second , and the third , will strongly hold them both in the aire , Tab. XII . Fig. 9. all of them being armed and communicating their vigors together firmely to vnite .

So a dagger or sword excited , will lift vp one waight at the end of another , and if the vpper that touched the sword or Load-stone , be held an inch off , yet by the vertue that is extended within the orbe Magneticall , the waights will cleaue together still .

Set a short and small wier at the pole of a Magnet , and it will be erected , set another on this , and it also will be caried vpright , set on the third , and all three will be apprehended and borne vp , Tab. XII . Fig. 7.

Also set a short wier on the pole , and another on a meridian , not farre off the pole , or set them vpon two seuerall meridians , vpon a strong Magnet , then lay another short wier on their heads , & they will hold and carry it , and this also will carry another wier vpon his backe , Tab. XII . Fig. 8.

There be certaine formes of Magnets , as the Semiterrella , in fashion of an halfe boule , the long ouall made plaine at the bottome , the long square formes , described , Tab. II. all these may be armed and capped with two teeth , at right or oblique angles to the axis , which being thus prepared , will apprehend great waights , and retaine them most firmely in the aire , Tab. XI . 12. 13.

If two Magnets , armed with two teeth apeece , be set before vs , the one being strong , the other weake , or much lesse , whose axis or diamiter betweene the teeth is equall of like length , then set the teeth of these together that come from contrary poles and parts , and the stronger will apprehend and lift vp the weaker , and the weaker being vnited and incorporated with the stronger , by the vertue that he receiueth from the stronger , will lift vp from the ground , and retaine the stronger and greater very firmely , although he be much heuier then the waight , the small stone doth ordinarily lift vp , Tab. III. Fig. 12. Tab. XII . Fig. 10.

Let a Magnet be armed with two teeth descending , and two ascending , as Tab. I. Fig. 5. & 6. the vpper teeth will cleaue fast to a great waight of iron , and hold by the same firmely , apply a waight to the : nether two teeth , and all will be retained and held together most firmely by paralell vertue of the meridians from the axis .

Such Magnets as be armed to one superficies , with foure or fiue teeth , or more , Tab. XII . Fig. 11. 12. must needs apprehend more and greater waights , retaine and lift them vp most easily .

A peece of steele well tempered , being excited , will lift vp a greater waight then the like forme and bulke of iron will , also this tempered mettall in a kinde of forme might be capped like a Magnet .

It hath bene proued that the apprehension is better betweene the bare stone and iron , as also the armed Adamant , with the armed Adamant , is most strongly retained , and farre more firmely then the retention of one Loadstone is with another small and bare stone .

Now it is to be obserued that steele , by reason of his drinesse , 〈…〉 his vigor Magneticall , bestowed vpon him , better then the iron doth that is softer , which entertaineth the vertue Magneticall sooner , and retaineth it the lesse time where his substance is lesse extensible and glutinous ; so steele being very often excocted and euaporated in the fire , becometh very brittle , and will not receiue the Magneticall vigour , yet being reduced from that hardnesse , and easily tempered , not to be ouer hard , will retaine the vigour Magneticall better then iron .

Those Adamants are the best which are bare and naked without their furniture and armor to take vp their owne waights , or more , at one of their points and poles , and retaine the same firmely . Such Adamants will cleaue vnto a peece of iron by their meridian , and hang vnto it , and will retaine a great iron waight also adhering to the meridian paralell to the Axis .

CHAP. XXV .

Of Magneticall direction from the earth .

HItherto I haue discoursed of the Magnet , and other Magneticall bodies , parts , motions , applications , vertues and effects , as they haue one vnto the other , which haue bene of that qualitie , that they might be almost all of them experienced and obserued at home and in our houses , handling the Load-stones as little earthes and globes , and turning them about with our hands , to see , obserue , and vnderstand all the qualities , vertues and effects of the same whatsoeuer , comparing these Magnets , as diuerse earths and Magneticall globes together , with the motions , compassions , and conclusions , proceeding from a present , perticular , and vnnaturall cause and potency in the stone before our eyes .

And hauing before partly discouered the motions that Magnets haue with the earth , being taken out of the same , and bred , and animated therein , as also the motions of such irons as haue bene excocted out of the mines , and such like veines , or rather bones of the Earth , that haue bene also endued and excited with the directory and Magneticall vigour from the Earth , both at their first forging and forming , as also by their placing vpon the ground whilest they coole , and become tractable with our hands , and their position in houses , windowes and other places .

Also I haue shewed how this vertue directorie , polar , vigour , and politie is to be giuen to compasses for the sea , & to directory needles , that direct our moueable dials into the meridian line , and to the Inclinatory-needle , or any other needle or Mathematicall instrument whatsoeuer .

Now I am to declare how such demonstrations as haue bene learned at home out of the Terrella and Semiterrella magneticall may be put in practise and vse by such as saile to farre countries by sea , or trauell by land , for their great benefit , both to teach them how to direct their course , and to tell them in what place and climate they are in , which thing they may performe and learne very perfectly , hauing the directory in their compasses , and the Inclinatory-needle in the meridian ring artificially made about them .

In comparing the two Magneticall bodies of iron , and the Magnet with the earth , the great and mother Magnet of all Magneticall bodies , we shall see and behold , that not onely in the Load-stone the Terrella and Semiterrella , but principally in the great Terra and Magneticall globe of the Earth , there is naturally found the two poles , the North and South , the aequator , the meridians , paralels , axis , and horizon , whereupon all the motions and conclusions that haue bene made vpon the meridians of the sayd formes in the Magnet , are proportionably and agreeably to be found in the Magneticall globe of the earth , in passing about her meridians , for all Magneticall motions are performed vpon the meridians principally , as hath bene said . Therefore place any Magneticall body , as is vsed to be done , free from all obstacles , Tab. XI . Fig. 5. 6. that may hinder their motion and conformity , and they will be situated conformably vnto the meridian of the earth , because that the earth hath primarily , naturally , & from her first creation , all Magneticall faculty , vigour , vertue , power , and potency in her selfe .

And first if a Magnet whose poles are knowne by the Art before taught , be placed in a boate , or boule of wood , and put into a great bason or boule of water , it will conforme , direct , and seate it selfe North and South , according to the same position and meridian that passeth directly vnto the poles of the earth ; Likewise take a Magneticall needle that hath bene excited with the Adamant , such as be in moueable dyals , or else take the Marriners compasse , and place them in quiet situation , and they will be directed by the disponent vertue and Magneticall vigour of the earth towards the North , and Southpoles vpon the true meridian circle and line , if there be no obstacle .

All direction is obserued by Magnetical bodies , especially by the directory-needle and compasse vpon one certaine horizon , whose center is in a meridian cut by some of the paralels , and on this center the needle and compasse is supposed to be placed , being truly peased and composed , that they may play , turne too and fro , and rest leuell and paralell vnto the horizon , fitly placed vpon a pin of brasse or siluer , and be well touched and excited , to the end they may be directed more certainely towards the poles vpon the meridian , Tab. XII . Fig. 13.

All Magneticall needles would be touched with a good vigorous and bigge Load-stone , that being capped lifteth vp at least halfe a pound weight of iron , to the end it may carry the flie and card of the compasse more strongly to his true direction and situation ; all needles and compasses that are to be animated and excited with that part of the Magnet that seateth it selfe North , swimming in a dish vpon the water , by the disponent power of the earth , and being freed from out of the orbe and vertue of other Magneticall bodies , these are turned and directed by the vigor of the earth into the South vpon the meridian line .

Euen so a rod of iron that stath bene placed North and South in a window a long time , whereby he hath receiued a true touch of polar vertue from the Earth , being within the orbe of his vigour , and being remoued from this position , which would be noted with chalke , and hanging leuelly in a string in the aire , will moue his North part , and seate it in the South quietly .

Therefore all Magneticall bodies , whether it be the Magnet that is taken out of the Earth , or a part of a Magnet taken out from this stone , that was cut immediatly out of the earth , or any iron or steele that is excited , either from the earth , from an Adamant , or from another excited needle , iron , or knife , or long forme of burnt clay , all these whatsoeuer receiuing their directiue and polar faculty from another Magneticall body , being set at liberty artificially in the aire or water , to moue and turne , will seate and be directed to the contrary pole they were first reuiued by .

Euery part from the aequator to the pole doth giue a polar and Magneticall vertue vnto diuerse formes of iron and steele to moue vnto a contrary position , by the directiue faculty of the earth .

This faculty directiue is as strong vpon the aequator as elsewhere , though it do not bestow it to others , being fortified from both prouinces on either side , and when the needle and compasse shall be in the aequator of the earth , because their libration and leuelnesse is all one with the horizon : therefore here the direction is conformable and strong : but in other places , and neere the pole especially , the leuelling of the needles is more violent , because they would incline and make an angle with the axis , and therefore the direction here is thought by some to be very weake : yet in this place neere the pole in the Terrella and Semiterrella , the little needle on his foote beareth himselfe most strongly and stiffely , that being with a finger turned awry , it will turne againe to his direction very violently , though inclining to the stone , and rest it selfe very speedily , without many turnings to and fro , so that neere the pole the direction is very strong , neither by leuelling hindred .

Alwayes and in all places the Lilly of the compasse or crosse of the directory-needle standeth and is seated into the North , both in this North side , and on the other South side of the aequinoctiall line or circle of the earth , Tab. III. Fig. 9. Tab. XII . Fig. 13. contrary to the syte of the needle neere the Terrella or Semiterrella , because they are touched and excited at that point of the Load stone that in his boate resteth South , and being set at liberty from the Loadstone by the earth is turned North , as the point touched at the North-pole of the Adamant is turned South , neither needeth there here any conuersion of the compasses in sailing and going from one prouince of the aequator to the other , as the needle idoth towards the Magnet being masculine , and the needles of iron or steele feminine , but the needles to the earth are perfect Magneticall bodies , and do keepe their correspondency with the earth , as if they were Magnet stones , or diameters of little earthes : therefore the needles and compasses passing from one side of the aequator to the other , in a meridian and great circle , proceedeth on still in a right line vniformely , onely the points of the needles and compasses do take their turnes to be predominant in their direction in their owne prouinces , especially if their leuel would suffer the vertue Inclinatory to preuaile , which thing is most apparant by the Inclinatory-needle in his ring , that being on this side of the aequator erecteth his lilly aboue the horizon towards the pole , but on the further South side of the aequator dippeth his Lilly vnder the horizon , and suffereth the Point to respect his owne pole with conuenient angles to the axis . But this thing cannot be done by the compasse and directory-needle , which lye alwaies paralel to the horizon , but onely is demonstrable by the stone in the 4 and 5 tables before .

This were a fit place , to speake of the order of making Sea-Compasses , the instruments for Magneticall direction , the making whereof is very well knowne vnto Artificers , yet I could wish , that they were more artificially made then they are , though the price were some-what more , with some additions , which wee do partly touch in the Chapter following , and wish also that the points were 48. in vse , that euery point might be halfe an hower .

All direction is performed vpon the true Meridian respecting directly with the Needle the poles of the earth , as the Needle doth in the good and pollished Load-stone and Terrella , vnlesse it be weakened , depraued , and forced to decline from the true Meridian of the earth , by the causes of variation .

CHAP. XXVI .

Of the variation of the Compasse from the true Meridian .

Tab: XIII diagram

But because the Globe of the earth is knowne vnto vs , to bee very vn-euen and vn-equally mixed , with many materials , differing from Magneticall substance , hauing great and stony Mountaines , large Vallies , deepe Seas , long and high Continents and fore-lands , some with mighty scattered rockes of Loadstone , of Iron-Mines , and other Magneticall matter , and some without , as also the entrailes , and interiour substance , barke or scarfe of the earth , consisting of a great quantity of substance not Magneticall , whereupon it commeth to passe , that when the Magneticall faculty of the earth shall direct these Magneticall instruments of the Needle and Compasse , they are not composed or set directly vpon the true Meridian that passeth right on to the poles of the earth , but are drawne and forced awry towards some vigorous and Magneticall eminency of the earth , whereby the Meridian which the Needle and Compasse maketh doth decline and vary from the true Meridian of the earth , certaine parts & degrees in the Horizontal circle , which is called the variation of the Compasse ; the Meridian that this declination of the compasse & needle maketh , may be termed the Magneticall Meridian , to distinguish it from the true Meridian , and the space betweene the Magneticall Meridian , and the true Meridian is the difference of variation ; So that here the needle & Compasse do dispose themselues into the North and South obliquely , and not truely and exactly , and according to the diuersity and strength of the scattered Magneticall bodies , being the causes of variation , the arch of the declination is greater and lesser , as in sayling by great Continents , and High-lands Magneticall , either the point or taile of the Needle , and Compasse , is forced awry towards the East or West , as is demonstrated in the chapter of Applications , & in the XXIII . Chapter .

For if the Magneticall eminency , whether it bee iron like clay , myne of iron , or rockeof Load-stone , be contiguous vnto the Magneticall Globe of the earth and fastened in the same substance vnto it , then the Compasse and Needle will leaue the direction of the Magneticall Globe of the earth , and deflect towardes this eminency , but if this Mountaine Magneticall be not continued with the Globe , and haue other Materials vnder and about him , then the Needle and Compasse will be thrust awry , and flye from it , declining as much , in a maner , the other way , leaning vnto it by the other point or taile , as it is demonstrated in the rule of Application of one Needle , in his varrying vpon the Load-stone , vnto a peece of Iron , touching and not touching the stone .

And no lesse doth the Needle and Compasse vpon the continent and inner-land , decline Easterly or Westerly , when as a great part of the earth shall bee of a substance no way Magneticall , and the other part shall bee of a vigorous and Adamantine quality to attract vnto it .

For although all direction to the North and South by the Needle and Compasse , be from the vertue of the whole Magneticall Globe of the earth , yet a strong effectuall , and neere perticular cause , though weaker , as it is proued in the end of the XXIII . Chapter , varieth their direction diuersly , and erratically , by that Land especially which lyeth and treateth North and South .

Where as the vigor and potency Magneticall increaseth from the Equinoctiall to the poles of the Magneticall Globe of the earth , as it doth in the Terrella , whereby the like eminency Magneticall , in the parts neere the poles , be of more allicient and Adamantine property , then they are about the Equinoctiall , therefore it may bee thought , that in sayling vpon one Meridian , in like distance , from this eminency , enriched with this vigour , it will make a greater variation of the Compasse neere the pole , then it doth neere the Equinoctiall , but this matter may bee helped and lessened by the great vigour that the needle is directed withall from the Adamantine . Globe of the earth , especially if the Seas bee shallow , and the Needle in a neere Orbe vnto the same , for thus the Needle will very hardly bee remoued , because the force of the earth is great that directeth it , but marke that in the XXIII . chapter , where a smaller strength Magneticall altereth quickely the retention of the whole more vigorous Magnet .

Also it is thought , that the variation of the compasse is much furthered by the naturall inclination of the needle and his conformity to an high-land , along the Meridian , betweene the aequator and the pole , like the demonstration of the Tab. VII . Fig. 2. where the long Load-stone varieth the Needle from the Meridian by little and little to a right angle , so if it could bee found out , that a neere perticular cause were so potent to vary the needle , as the long-stone , there is the side of the land would vary much , but the cap farre more , also at the aequator , as in the Tab. VIII . Fi. 5. an eminent part of land , ending at the aequator , might vary the needle much , as is there demonstrated .

Although these applications be great inducements that there should be such positions of the Compasse , in some places betweene vigorous lands , to be obserued , yet because that these eminences from land , are not any particular and complete Magnets of themselues , but adherences and protuberances of some part of the Magneticall Globe , and haue their nature according to the vigour of that paralell where they stand , and haue not euery one of them a pole neere their caps and angles , as these Magnets haue , in their demonstrations set downe . I cannot wholy approue them for sufficient demonstrations of variation , though they may helpe very much for the vnderstanding of the same .

Therefore , for the better knowledge of the variation of the Compasse by the Terrella , it is very conuenient to apply a strong Magneticall body vpon the Terrella , alongst the Meridian , or a little obliquely , then carrying a little needle vpon the Terrella , the needle will vary more from the true meridian neere the aequator , then it will doe neere the pole , because the Needle neere the pole is directed very strongly and stiffely by those parts , and will hardly bee forced from his direction .

But let the eminency bee very vigorous thicke , and about twenty degrees high , then hold the Needle so high from the Terrella in that Orbe , then the Needle is to be conueyed from the aequator to the pole , and first bring this eminence towards the Needle , and it will beginne to vary from his direction , being within twenty degrees or parts of the eminency , and so increase his declination continually till hee bee varied towards sixty degrees , in the parts neere the aequator , and about fifty degrees , at the most , in the parts neerer the pole in the same Orbe , therefore the deeper that the Seas are , the greater is the Magneticall Orbe , and the more subiect to suffer the Needle to bee attracted by a neere eminency , and the shallower that the Sea is , the lesse is the Magneticall orbe of the earth , which more hardly suffereth the Compasse to vary .

This is to bee noted that high-eminences and lands neere the poles , being before the Compasse doe not cause the same to decline , but onely such eminences as are placed according to the Meridians , and trent North and South , or obliquely a little on either side , to these the Compasse will be attracted awry from his true direction .

But if there be a narrow passage betweene two high-lands , then the Compasse and Needle will respect neither eminency , but carry and direct it selfe paralelly betweene them both , when the strength of two high-lands is of equall force ; as it is demonstrated vpon the Terrella , and not vnlike to the figure , Tab. VIII . Fig. 3.

This is to be obserued also , that the middest of an high-land , by demonstration vpon the Terrella , doth attract most , and make the greatest variation , and towards the ends it decreaseth by little and little , and once passing by the eminency it varieth the compasse no more , and it is likely so to do vpon the earth .

If there be a Magneticall rocke lying sidelings vnder the water , it will make the needle vary a little from the true Meridian .

Therefore the farther that the Compasse is distant from an high-land , that attracteth , the lesse is the variation , and passing further out of the orbe of his vertue there will be no variation at all , vnlesse the deepes and substance of the earth bee partly Magneticall , and partly of different substance , For these causes it is obserued , that places of a small distance assunder do differ much in their variation , holding one proportion , neither in passing vpon a meridian , or on a paralell , yet in one and the selfe-same place variations neuer differ , but remaine certaine and constant .

The West-shore of a magneticall continent doth make the variation of the compasse Easterly , and the East-shore of a maine-land beholding the Sunne rising attracteth on the North-side of the aequator , the Lilly of the Compasse that it decline West from the true Meridian , on the South-side of the Equinoctiall the point of the Needle is attracted , Table XIII . Fig. 1. 2.

About the Ilands of Azores the Compasse hath little variation , as at Fayall the Compasse varieth to the East three degres , and at Coruo the variation of the Compasse foure degrees to the West .

Some thinke that Ilands , though Magneticall , make no variation , being too weake and feeble in regard of the great strength of the directiue globe of the earth , which directeth the needle and compasse , because that the Iland of Elba , neere Florence , being ful of Loadstones , causeth no variation of the compasse more then other places neere adioyning do , but if vpon the Terrella , as in the XXIII . chapter there be neuer so litle wiers applied neere a needle , it will deflect towards them , so that here perfect obseruation may be desired , which by the common rules is long and tedious to performe : therefore I will set downe ready and easie wayes to obserue the true meridian by the Sunne , that the variation of the compasse may be plainely perceiued , and that in a moment , by one obseruation only , to the end that industrious and skilfull pilots will in time furnish themselues and the world with the true obseruation of variations in all parts of the world .

CHAP. XXVII .

Of finding the variation of the Compasse by one obseruation .

FOr this purpose there are certaine things to be knowne , and obseruations to be had in a readinesse before this conclusion be found out , first the place is to be set downe by name or note , where this obseruation is made ; then the altitude of the pole in that place is to be knowne and set downe , after the day of the moneth ; and the declination of the Sunne are to be set downe , all these things skilfull pylots know very well to performe . Then hauing a good sea-compasse for the water , and a large directory-needle for the land , it is necessary vpon the outmost part and circle of these to haue a limbe or verge a quarter of an inch broad for the horizontall circle , and to haue the one halfe of it deuided into two ninties of degrees , with his conuenient parts and figures , as is vsuall in all quadrants , beginning the numbers from the meridian-line , and ending them at East and West .

Next prouide a diamiter somewhat longer , then that of the circle , of brasse , wier , or siluer , hauing in the middest or center of it a small wier of the same mettall , fastened and soudred vnto it at right angles , as a Semidiamiter , all this being framed will be like in fashion to the beame and tongue of the ballance of a paire of scales , Tab. XIII . Fig. 3. and iust at the East and West put this diamiter through two holes of the sides of the compasse , or fasten it there with two loopes of brasse , that you may turne the semidiamiter vp and downe iust ouer the center of the compasse and needle , and this may be set vpright at either end , with two little shoulders of brasse to keepe the semidiamiter vpright and perpendicular vnto the horizon .

Hauing the compasse and needle thus furnished , place the needle and Lilly of the compasse iust against the beginning of the diuisions , then set the compasse before the Sunne , with this semidiamiter erected where the compasse and needle standing in their Magneticall meridian , the shadow of the Sunne from this semidiamiter will shew vpon the degrees of the limbe the Magneticall position , and azimuth of the Sunne , which is presently to be noted downe , as it is East or West .

Note that at sea if the ship turne any thing about , the boxe of the compasse must also be turned , that the meridian of the flie may be alwaies against the beginning of the diuisions .

Likewise , because of the ships vnsteadinesse at sea , it is fit to haue a wier erected from the center of the flie , whose shadow among the diuisions , vpon the flie of the compasse , will shew the Magneticall azimuth .

Then instantly hauing a Iacobs staffe at sea , and a quadrant at land , take the altitude of the Sunne , which is to be noted downe , and after at pleasure and leysure , hauing these petitions , the variation of the compasse for that place may thus be had .

Take M. Blagraues Mathematicall Iewell , or the Astrolabium Catholicum , set out first by Gemma Frigius , which is not so ready as this , because it lacketh the rete which this hath ; place the horizon of the rete to the altitude of the pole for that place , and looke where the Sunnes altitude that was obserued and almicantareth crosseth and meeteth with the paralel of the Suns declination for that day before set downe , and the azimuth or verticall circle that crosseth these two in that point where they touch , and this is the true azimuth of the Sunne from the true meridian , which differing from the Magneticall azimuth as first obserued vpon the compasse , the difference of these two azimuths is the arch of the variation of the compasse , and of the Magneticall meridian from the true meridian , which is to be set downe , that this is the variation of the compasse towards the East or West for that place .

CHAP. XXVIII .

Of finding the variation of the Compasse , by the circles of the Astrolabe .

FOr this purpose the petitions required in the former chapter , are to be writ down , and in a readinesse , as the place of the obseruation , with the altitude of the pole in that place , the day of the moneth , with the declination of the Sunne for that day , the

Tab: XIIII diagram Magneticall azimuth , and the altitude of the Sun for that one instant of obseruation . Now in describing the circles of the Astrolabe for this purpose , first vpon a line B E D at the center E make a circle a B C D , and by the center E draw the line A C at right angles to B D from A towards B , number the altitude of the pole , to which point apply a ruler from D , cutting the line A C into the zenith point F , set one foote of the compasses in F , and describe an arch towards B at any distance aboue and below , after the compasses vnremoued set the foote of the compasse in B , and cut the former arches into points , vnto which applying a ruler , draw an obscure line to deuide the line A C produced into K , from the center K , according to the distance to F , describe the verticall circle F G H I , making the line K G I at right angles to F H , now from A towards B number the declination of the Sunne for the day proposed for the North signes , and towards D for the South signes , place a ruler to this point and to D , cutting the line A E into L from the center E , as is the distance E L , describe a circle for the paralell of the Sun , next from D towards A , number the altitude of the pole to M and by the center E draw an obscure diameter M , E , N from M N towards A B number the altitude of the Sun before obserued , applying a ruler from D to each deuision , to cut the line A C in two points from the middest , as a center betweene these two , and by them describe a circle for the almicantarath of the Sun , deuiding the paralell of the Sunne at O , from O and F make obscure arches to cut one the other , from whose center P to O F , describe an arch of a circle for the true azimuth . Which to know what it is , draw an obscure line from F by P , to the circle F G H I vnto q , then deuide the arch q h in the middest at r , and the arch g r resolued into degrees , shall be the distance of the true azimuth from the meridian . The difference of the Magneticall azimuth from this azimuth , sheweth the distance of the meridian of the compasse from the true meridian , which distance is the variation of the compasse for the place obserued .

A short way vpon land to draw the meridian line vpon a plaine superficies leuelled to the horizon ; immediatly before the obseruing of the altitude of the Sun , hold a plummet by a thred , that the shadow light on this superficies , in this shadow make two prickes to be ioyned together in a straight line , after out of this type set the angle g k r , which shall be the meridian from the line of the azimuth mad●●y the shadow .

CHAP. XXIX .

Of finding the variation by the Analemma .

BEeing furnished with the petitions , before recited in the former chapters , make this Analemma , about the horizontall line A E C , describe a meridian circle , and make the verticall diamiter B D by E , at right angles to A C , then from A to F in the quadrant A B , number the complement of the altitude of the pole , and by E draw a line F G for the intersection of the aequator & meridian , them number from this aequator on both sides the declination of the Sun for the day of obseruing , being 10 degrees , and from the points draw the line H I for the paralell of the Sunne , next in either quadrant aboue the line A C , number the altitude of the Sunne before obserued to be 30 , to k and l ioyne these two

Ta: XV diagrams together in a line paralell to A C the horizon , passing through the center of the Sunne , and cutting the verticall line B D into M , and the paralell of the declination of the Sunne H I into N from M a center , describe a semicircle to k l , and from n draw a perpendicular line with k l vnto this semicircle , deuiding the same in O , and ioyne m O by a line together for the distance of the azimuth from the true meridian , which being resolued into degrees , and compared with the Magneticall azimuth , the difference betweene these azimuths sheweth the degrees of the variation of the compasse .

CHAP. XXX .

Of finding the variation of the Compasse by an Equinoctiall Diall .

PRouide in a readinesse , an vniuersall Equinoctiall Dyall vpon a plaine , that may artificially be erected to the height of the complement of the Latitude of the pole , for the place of obseruation , and vpon the center of the Equinoctiall-circle place a ruler , and at eitheir end of the ruler erect a plate of brasse , little more then a quarter of an inch broad , that may with iointes conueniently bee raised at right angles , to the ruler and superficies of the Dyall , and vpon these plates place the diuisions of the Trigon of the twelue signes , after this manner . Tab. XV. Fig. 2.

Draw a straight line a b , and from a center , describe a quadrant of a circle to c , and let c a cut a b at right angles , then deuide the quadrant c b into ninty degrees , then from b towards c number the greatest declination of the Sunne , which is 23 degrees and an halfe , ending in d , and at d draw a line at right angles , to a b , which is d b , and set the length of the line d b from a to h in the line a c , then produce the line a b , obscurely to e , and from b as a center according vnto the distance b d , make an obscure semicircle ouer the line a b e , deuide this semicircle into sixe parts , for sixe signes , euery diuision containing 30 degrees , when it shall bee sub-deuided then ioyne these diuisions together in paralell lines to a b e , for the beginning of the sixe South-signes , then from d b draw a paralell line f g , according to the bredth of the plate , and from d to f make a paralell to a b e in d f , the plate being some-what higher , make an hole , as in a Diopter , that the Sunne may shine in at it in Summer time , vpon the other plate at a h for the North-signes , which plate a h i k , would bee of the same bredth and height that b d , f g is , then let the obscure paralell lines of the beginning of the South signes bee drawne vpon this plate , place ♎ Libra aboue the line b g , ♏ Scorpio aboue next line , ♐ Sagitary aboue the next line , and vnder the line d f place ♑ Capricornus , vnder the next ♒ Aquarius , and vnder the next ♓ Piscis , the other plate for the North-signes , mnst haue the same paralell lines in it that this hath , for the beginning of the North-signes , and an hole in it for the Diopter , that the Sunne may passe through it to the first plate of the winter-signes to shew them that part of the plate or end that hath the Diopter in it is to bee placed in the line b a k , contrary to the situation of the paralels in the first plate , & vnder the vpper-most line h i , place ♈ Aries , vnder the next ♉ Taurus , vnder the next ♊ Gemeni , then aboue that line that hath the Diopter , in it place ♋ Cancer , aboue the next ♌ Leo , and aboue the next ♍ Virgo , so is all the characters of the signes placed in their plates , let the ruler be of the bredth of the plates , and in the middest of it draw a line , and in the middle of it make a hole of the center L , the better to bee fastened to the center of the Equinoctiall : k and m must bee artificially ioyned with ioynts together and g n , at which the ruler from l is produced to make an Index vpon the Equinoctialldyall to shew his howre as it is Tab. XV. Fig. 2.

More-ouer , there is to be placed in the foote of this Equiquinoctiall Dyall , a large directory-needle , hauing his outer-most circle diuided into foure ninties , beginning to number the parts from the Meridian to the East or West .

This Equinoctiall Dyall being thus furnished with the ruler and plates for the Zodiake and the directory-needle , and erected to the Equinoctiall of the place , where the obseruation is made , turne the whole frame of the Dyall and ruler about with his plates , vntill the Suune-shine directly vpon the signe and parts that he is in for that day , then his whole frame will stand in the true meridian , and the directory-needle will stand in his Magneticall meridian , and point out so many parts in his horizontall circle , as his variation in that place is to the East or West , which is to bee noted downe , and the ruler in the Equinoctial circle sheweth the true hower and part of the Sun , for that day and instant .

Tab: XVI . diagram

CHAP. XXXI .

Of finding the variation of the Compasse by Rings .

THere is an other instrument consisting of foure ringes of Brasse , one to bee placed within the other , which is an vniuersall Dyall , hauing a directory-needle in a boxe , fastened at the bottome of the same , which doth shew likewise presently the variation of the compasse hanging perpendicularly , Tab. XVI .

The first two rings of this instrument are two meridians , the outer-most is broad , and hath a ring to hold it by , fastening it to the vpper end or top , and the North-quadrant towards the ring or handle is diuided into ninty degrees for the numbers of the altitude of the pole , also this ring hath fastened vnto it at the bottome a directory-needle in his boxe , the limbe whereof is diuided into two ninties from the meridian to the East and West .

Within the ring of this broad meridian , there is an other meridian-ring placed , so kept on the sides , that it may bee moued higher or lower , so that his broad Index , fastened vnto one of the foure quadrants , may bee set to point out the degrees of the altitude of the pole , this Index hath a lower end for to stay the fourth ring that carrieth the Trigon of the signes , and a thred like an axis with a moueable beade thereon .

The third ring within the second is for the Equinoctiall circle , and it is fastened to the moueable Meridian-ring at right angles to the eleuation of the pole by two pinnes , whereon it may bee moued at right angles to the meridian , though it will be laid within the said meridian , in the inner part of this ring there is a circle to bee drawne for the Equinoctiall circle , and to bee diuided into 24 parts , for the howres of the day , from the meridian ; and sub-diuided with conuenient lines and figures .

The fourth ring is fitted within this Equinoctiall ring , and at sixe of the clocke , or at the East and West is fastned to it with two pinnes , to moue at right angles vnto the same , this carrieth an axis which being moued about is stayed by the nether end of the moueable meridians index , descending into a nicke in it to hold it at right angles with the aequinoctiall-circle in manner of a sphere , and holdeth the said circle at right angles with the meridian , within this fourth ring , whose axis is stayed by the Index from either side of the aequinoctiall , hauing the center in the aequinoctiall at the side of the ring , there is described aboue it , and below it , the greatest declination of the Sunne , and the arch betweene the same and the aequinoctiall is diuided into such parts for the beginning of the twelue signes as the plates before were in the former chapter , adding the characters of the twelue signes , as it was there done ; then at the sides of this ring in the aequinoctiall where the center of the fore-said declination was taken , fasten the head of a pin of brasse , and from it beholding the signe & place on the other side that the Sun is in that day , and betweene the eye and that place in this line place the beade vpon the axis and so fixe it .

Now hauing this instrument thus prepared , set the Index of the moueable meridian vnto the altitude of the pole , and mouing the Equinoctiall circle , and the colure-circle or different of the signes , and fasten it firme at the lower end of the Index , hold the instrument by the ring , or handle , like a sphere perpendicularly , and turne it too and fro till the shadow of the bead light vpon the middle line of the aequinoctiallring , thus the meridian of this instrument standeth vpon the true meridian , the shadow of the beade sheweth the howre and his part of the day , & the needle in the boxe pointeth out the variation of the compasse in the limbe of the horizontall circle .

These rings , at pleasure , may bee folded one with in the other for conueniency of cariage , and in time of vse set abroad like a sphere .

Any vniuersall , or Astronomers ring , would bee of especiall vse for the finding of the true meridian , as well as these , and hauing the needle added vnto them , the variation of the compasse would be found .

CHAP. XXXII .

Of finding the variation of the Compasse by an Horizontall Dyall .

WHen I was a yong student in the Vniuersity and delighted in making of Dyals , I was alwaies wont to place the lines of the twelue signes in them , that when I set any bodies of Dyals in the Sunne , vpon a leuell foot , I alwaies directed them by the shadow of the Sunne vpon his signe and part into the true meridian and South , and hauing a large horizontall Dyall for any Region , with the lines of the twelue signes described in it , placing the same vpon a leuell plat-forme , and turning it vntill the nicke of the shadow of the stile light vpon the place and signe that the Sunne was in for that day , then fixing a compasse or needle with his meridan paralell to the meridian of the Dyall , the needle will shew in the limbe of the horizontall circle the variation of the compasse , and the Dyall sheweth the howre and his part of the day .

This Dyall might bee made vniuersall as well as the aequinoctiall , if that in trauelling North the North side were eleuated by meanes of a quadrant , that the plaine of the Dyall might alwaies haue the pole of the Dyall erected aboue him to that latitude for which it was described , and in passing Southerly the South-side of the Dyall would bee situated by the quadrant to his propper eleuation .

And if that the Azimuths and Almicantars were put into this Dyall , then the Azimuth and altitude of the Sunne , with the place of the Sunne and howre , would be presently shewed by the shadow of the stile , so that for these purposes , this horizontall Dyall would bee made vniuersall , as a generall Astrolabe or Astronomicall ring .

CHAP. XXXIII .

Of finding the variation in degrees and minutes by the doctrine of Triangles .

WHereas many may be desirous to know precisely the degree & minutes of the variation of the compasse , for to satisfie these mens appetite , it is very conuenient to vnderstand the doctrine of Triangles , for by the Tables of sines , Secants , and Tangents , with the Axiomes and consequents , & the Golden rule this , matter wil be attained vnto . And therefore for this purpose , I would aduise you to obserue and marke the frame of the Analemmaset set downe before in the XXVIII . chapter , Table XV. Fig. 1. with the obscure lines pricked therein .

First in this Analemma let G C equall to A F bee the eleuation of the aequinoctiall line , consisting of 38 and an halfe , which being called to C L 30. the Sunnes altitude at the instance of obseruation for that day , and the some of these will bee 68. ½ whose Sine is the obscure pricked line L P , now take A K 30. degrees being the Sunnes altitude , out of A F the aequinoctiall Altitude 38. ½ there resteth K f 8 1/● , whose sine is the obscure line pricked q K , which added to L P. produced make L P S , 77.

Diuide S L into two equall parts ending in t , and take from S t , being 38 ½ the sine of the Sunnes altitude K q 8 ● and take also out h r being 10 , the signe of the Sunnes declination , and there will remaine t V being 20 , then ioyne t and m together in an obscure pricked line , and make a line at right angles to this from m to x being 20 , and is equall vnto t V , so haue you this demonstration , and if you looke into the Table of sines for the numbers , you shall finde them set downe in their place .

And as the sine of t l is vnto the sine of l m , so is the fine of x m vnto the sine m n.

So that the angle M B K in the Analemma being the complement of the angle M B N , will be the Azimuth you sought for , and it is equall to the angle O m D in the said type , which compared with the Magneticall Azimuth , the difference betweene them sheweth what the variation is from the true meridian .

Secondly , it is to bee noted , that if this obseruation , or taking of the Sunnes altitude be before 6 a clocke in the morning , or after at night , when the Sunne is in the North paralels , that N the intersection of the Sunnes altitude and paralell of the Sunnes declination bee on the same side of the Analemma that t is on , then take h r the sine of the Suns declination out of l t , and there will rest t V , ioyne t and m together , and make a small line at right angles from n to x , equall to t V , for as t l is to k m , so is x n vnto n m , &c.

Thirdly , and lastly , if obseruation bee made when the Sun is in the aequinoctiall , then make the smal line m x equall to P t , and looke what proportion t l hath vnto l m , the same hath x m to m n where n is on the aequinoctiall line , &c.

CHAP. XXXIIII .

Inclinatory-needle to the axis of the Earth .

WE haue shewed how the compasse and directory-needle do apply and order themselues in the Magneticall meridian towards the pole , and of the correcting of his erring from the true meridian and pole , being caried leuell and paralell to the horizon , and seated in any part of the terrestriall globe , whereby , and to the end the traueller by sea and land may take his course certainely , to any coast or part of the world . Now it remaineth that we treate of the vse of another needle , called the Inclinatory-needle , which being artificially placed in his ring , is as profitable to all Nauigators and trauellers , as that formerly spoken of ; for by this they may know the eleuation of the pole in all parts of the world without the sight of the celestiall globes and lights .

This Inclinatory-needle fitted in his ring , and placed in the Magneticall meridian , doth apply & conforme it selfe vnto the axis of the Magneticall globe of the Earth ( whereas the directory-needle doth apply vnto the meridian and pole ) and that diuersly in diuerse eleuations of the pole , for sailing vpon the aequinoctiall of the earth , this Inclinatory-needle maketh a paralellline with the axis of the earth , being vpon the pole , this needle will make one continued line and axis with the axis of the earth : passing from the aequinoctiall to either pole , this Inclinatory-needle will conforme it selfe vnto certaine acute angles with the axis of the earth , which increase from the aequinoctiall in largenesse , and proue lesse acute in euery paralell , so that the angle of the earths axis , and the axis of the needle is at the greatest about 42 degrees of the poles eleuation , and the difference betweene these two will be neere 22 degrees and a halfe , being here at the largest , after it decreaseth continually towards the pole , where the needle will stand directly vpon the axis of the earth .

Now to know and find out this angle what it is , it is necessary to learne what angle this Inclinatory-needle maketh with the horizon in euery latitude of the pole , because if the eleuation of the pole be taken out of this angle with the horizon , which is alwayes the larger , ( vnlesse it be at the aequinoctiall and the pole ) and hath the axis of the earth alwayes betweene him and the horizon , the remainder is the angle of this needles conformity with the axis of the earth .

Therefore we will leaue to speake of the Inclinatory-needles most naturall and true conformity with the axis of the earth , and hereafter shall deliuer by what meanes the angle betweene the Inclinatory-needle and the horizon may be knowne , to the end that the eleuation of the pole may thereby be found out .

CHAP. XXXV .

Of the Inclinatory Ring and Needle .

WHereas the horizon is very easily found out by any massie substance , which naturally will hang perpendicular and plumbe , by hauing a leuell line made at right angles vnto the same , therefore it shall be conuenient to place this Inclinatory-needle in a ring of brasse or siluer , so artificially , that this frame being caried about the meridian of the earth , this needle may make all kind of acute angles with the horizon in the varieties of his inclinations vnto him , as at the aequinoctiall this needle lieth leuell with the horizon , so at the pole it standeth at right angles to the horizon , and directeth it selfe in one line with the axis of the earth , and passing from the aequinoctiall , it doth eleuate it selfe aboue the horizon twise as fast as the pole doth , vntill the pole haue about an 11 degrees of latitude aboute the horizon , but after the needle slacketh his pace by little and little , vntill he come to the pole where both ioyne together without any angle at all in one line directly .

Also this needle maketh alwayes one kind of angle with the horizon in one paralell and altitude of the pole , and a diuerse arch from the same , but one certaine in one latitude , as by this instrument following shall appeare , and euery where be obserued .

Tab: XVII diagram

After prouide two narrow plates of brasse or siluer , to be fastened on either side of the ring paralelly to the horizon , and in the middest of these , as it were , against the center of the ring , drill and make two little holes almost through the sides of the plates for the short axis of the Inclinatory-needle to play and moue in , vp and downe , according vnto this kind of Magneticall and Inclinatory conformity . Lastly , this instrument would be couered with two glasses for both sides to keepe the Inclinatory-needle from wind and weather , and a care had that the instrument hang truly perpendicular .

In time of vse in trauelling , hang this instrument South and North in the Magneticall meridian , and this Inclinatory-needle will fall with one end vnder the horizon in euery eleuation of the pole , and beare vp his other end in euery paralell and altitude of the pole to a certaine angle with the horizon , which may be called the Inclinatory angle for that place , which being noted in the meridian of this ring , with the degrees he pointeth at , is to be reserued as proportionable to that eleuation of the pole where the obseruation is made , this matter was demonstrated by the round Load-stone in euery part in the XIII . chapter before , which being collected by the sayd demonstration and practise , are to be placed in their correspondency in a Table for the altitude of the pole , wherby in all places it may be had readily what will be the angle of the Inclinatory-needle , and what is the latitude of the pole , caused onely by the disposition of the Magneticall globe of the earth , and also by the diagrams following it is shewed .

CHAP. XXXVI .

A Diagram of the needles inclinations to the axis of the earth , and horizon in any latitude .

THis demonstration sheweth most manifestly vnto our eyes , both what angle the Inclinatory-needle maketh to the axis of the world , or earth , in all regions , and also what angle or arch he pointeth at aboue or vnder from the horizon in any latitude of the pole whatsoeuer , hereby most euidently setting out the meanings of the two former chapters , and of the XIII . chapter before them , where it is demonstrated from the stone it selfe , that this Inclinatory-needle will make but one circumuolution about the meridian of the earth , as it doth about the Loadstone , the Diagram is this .

Tab● XVIII diagram

In like manner from the other ten partes , or 90 degrees , in the quadrant B D draw paralell-lines to the 〈◊〉 A D produced , and from euery part as a center extending the compasse from the same to C , describe arches from C to those lines , diuiding them into 90. parts a peece , and take like number of parts answering to these parts in the quadrant C D for the axis of the latitude , then draw an obscure line from A to the same part , in these larger arches , and that will shew the angle that the Inclinatory-needle maketh in his inclination to the axis and horizon in that latitude . We haue onely for example-sake deliniated the inclination of this needle to the axis and horizon , in the latitudes of 10. 30. and 60. the like whereof might bee performed in euery one of the other degrees of latitude , which thing is omitted to auoide confusion of lines .

What this angle of the inclination of the needle would bee in euery latitude of the pole , although by the Diagramme , already set downe , it might bee Mechanically taken out of the quadrant C D , as it is reduced into ninty partes . Yet I will set downe , how out of the cannons of Triangles , the arch from I to C , may bee exactly knowne in degrees and minutes .

In the Diagram G , A , B 30 ; the eleuation of the pole being set for an example , draw from G these obscure lines , as G F , G K , G C , G A , and A F , the line of inclination , the content of the angle A G C is 15 , C G K is 15. K G F is 20 , so that the angle of the Triangle F G is 18 , 50 , and the summe of the opposite angles , which marked vpon the semi-circle , will bee 130 degrees , whose halfe is 65 degrees , the tangent whereof is 214459690 , then wee finde that the line G F in the triangle is equall to G C , the Suhtenses of 150 degrees , the halfe or sinus hereof is 75 degrees , whose parts out of the Table of sines are 96592583 , which being doubled make the side G F 193185166. The side G A hath for his parts the totall sine 100000000 , the summe of these two sides is 293185166 , and the difference of them is 93185166.

Now multiply the tangent of 65 degrees 214459690 by the difference of the sides 93185166 , and diuide the product 42891938 by the summe of the sides 293185166 , the quotient will bee the difference of the tangents 146296413 , which taken from the parts of 65 the middle tangent 214459690 , the tangent parts that remaine 68163277 giue by the Table 34 degrees 16′ 47. ″

Here take 3416′ 47″ out of 65 degrees , there resteth 3043′ 13 , for the lesse angle A F G , so adde 34 16′ 47″ vnto 65 degrees , and it maketh 99 16′ 47″ , for F A G the greater angle , heereto adde 30 degrees the eleuation of the pole there amounteth 129 16″ 47″ for the angle F A B , which taken from the semicircle 180 , there remaineth 50 43′ 13″ for F A C the inclination of the needle vnto the horizon where the pole is eleuated 30 degrees .

I haue heere set downe a Table calculated out of this diagramme of the degrees and minutes of the angles of the Inclinatory-needle , with the horizon answerable to euery eleuation of the pole , by Mr. Brigges the Geometry reader in Gresham Colledge , who hath farre more ready and easy waies to make the fore-said Table , then I haue set downe vnto thee , and I thinke that this Table will agree more truely with the motion from the stone it selfe then that which is made by the same man out of the diagramme in the Chapters following .

TABLE. Eleuat . poli Inclinat ad horiz . G. M 1 2 2 2 4 4 3 6 6 4 8 8 5 10 10 6 12 11 7 14 13 8 16 13 9 18 12 10 20 10 11 22 5 12 23 59 13 25 50 14 27 39 15 29 25 16 31 9 17 32 50 18 34 28 19 36 4 20 37 37 21 39 7 22 40 34 23 41 59 24 43 21 25 44 40 26 45 58 27 47 12 28 48 24 29 45 35 30 50 43 31 51 49 32 52 54 33 53 56 34 54 56 35 55 55 36 56 52 37 57 48 38 58 42 39 59 35 40 60 26 41 61 17 42 62 6 43 62 54 44 63 40 45 64 26 46 65 11 47 65 55 48 66 38 49 67 20 50 68 2 51 68 43 52 69 23 53 70 2 54 70 41 55 71 19 56 71 57 57 72 34 58 73 11 59 73 47 60 74 22 61 74 58 62 75 33 63 76 7 64 76 41 65 77 15 66 77 49 67 78 25 68 78 55 69 79 27 70 80 0 71 80 32 72 81 4 73 81 35 74 82 7 75 82 38 76 83 9 77 83 39 78 84 10 79 84 40 80 85 10 81 85 40 82 86 10 83 86 39 84 87 9 85 87 38 86 88 7 87 88 35 88 89 4 89 89 32 90 90 0

CHAP. XXXVII .

Another Diagram of finding the angles of the Inclinatory-needle in any Paralell .

Tab: XIX diagram

But to make vse of this motion for the inclination , we shall onely set downe what aspects or angles the needle maketh with the axis of the earth at euery tenth degree from the aequator to the pole , where in this Diagram there be lines to the inside of the quadrant D B for the inclination of the needle , which may also be produced outward into the orbe of Magneticall vertue vpon the limbe , as it is set out in the twelfth chapter , Tab. III. Fig. 2. both in pricked lines , and also in the erection of a short wier at euery tenth degree of the quadrant : therefore for the better preseruing of this matter , we shall set downe the order of the making of this Diagram , as followeth .

Describe vpon the center E a meridian circle , as it were of the round Magnet A B C D , which diuide into foure quadrants , ioyning A and B for the axis , and C and D for the aequator , together with straight lines , which cut the one the other at right angles in the center E , deuide the quadrant of the poles eleuation D B into ninety parts , beginning from D , and ending the numbers in B , with the vsuall figures .

At D draw an obscure paralell line D F for the horizon , and from D , as a center according to the semidiamiter D A , describe an obscure arch of a circle A B F , deuiding the line D F in F , next vpon E , as a center according vnto the semidiamiter E F make an arch of a circle F G , and from B a center , according to the semidiamiter A B make an arch of a circle that cutteth the arch F G into G.

Then place the foot of the compas in euery part of the quadrant D B , as in center , extending the other foot to A , and describe arches to F G , and first place the foote of the compasse in the deuision of 10 in the quadrant , and opening the compasse to A , describe the arch of a circle from A to the arch F G , and deuide this arch from H into ninety parts , first into 3 parts , then part euery one of these into 3 parts , containing ten parts apeece , if they were subdiuided into them , then from 10 in the quadrant , to 10 in the arch from F G draw a straight line 10 and 10 for the line of the inclination , now draw an obscure line from E to the degree of 10 in the quadrant , and from this line at 10 make an obscure line at right angles for the horizon to E to , then take the semidiamiter D E , and place one foote in this line from 10 to H , and from 10 as a center describe an obscure arch H L to the line 10 and 10 , and this arch shall be the angle that the Inclinatory-needle maketh with the horizon , where the pole is eleuated ten degrees aboue the horizon , and the angle 10 E and 10 is the complement of the former angle .

Next place the foote of the compasse in the twentieth degree of the quadrant , and stretching it to A describe the arch of a circle from A to the arch F G , which being diuided into ninty parts , first into three parts , and these into three parts , againe draw a line from 20 in the quadrant to 20 from the arch F G , now make an obscure line from E to the 20 degree in the quadrant , and from this line at 20 make an obscure line for the horizon at right angles to E , 20 , take the distance from E 20 , and place it in the line 20 I , and from 20 as a center , the compasses being vnremoued , describe the arch I M , cutting the line 20 and 20 into M , which is the angle the Inclinatory-needle maketh with the horizon , and being set in the arch D B , the number of the degrees of this arch of inclination will appeare .

According to this order draw arches from A to F G , making the diuisions in the quadrant the centers , and their distance from A the semidiamiters of them , diuiding these arches as afore is done , and drawing right lines to the correspondent diuisions in their seuerall arches from the seuerall degrees in the quadrant , whose respondent angles of inclination is knowne by making at the same and describing arches according to their semidiamiter from E , as hath bene declared in the two former examples , which being reduced into degrees , by placing the arch in the quadrant D B , from D towards B , will shew the quantity of the needles inclination vnto the horizon and his angle with the same .

CHAP. XXXVIII .

Of finding by the Needles inclination vnto the horizon , the altitude of the Pole by an instrument .

〈◊〉 XX diagrams

Moreouer describe a moueable quadrant of the same bignesse and semidiamiter that E D B is of , to be moued vpon it in a paper apart , past-boord , or some mettall , whereon this instrument may be described , ( the larger the instrument is , the better it will be for vse ) therefore , according to the semidiamiter E D , describe a quadrant A B C Tab. XX. Fig. 2. from A the center , & deuide it into ninety parts , first into nine parts , then euery one of these into two parts , and euery one of these diuided into fiue seuerall degrees , thus will the whole quadrant be deuided into ninety degrees ; and at 90 degrees make a center at C , and from B to C set the figures on the outer space in the limbe vnto euery tenth part , as is vsed to be done , after a little halfe inch distance ; from the center of the quadrant A , describe a little limbe or stay , then cut out the inward part of the quadrant C B to this limbe or stay , and from the limbe to A cut out a part , that the semidiamiter A C may serue for an Index or ruler , Ta. XX. F. 2. Now bring this quadrant A B C thus cut out , & place , and fasten the degree of 90 where the center is at C , vpon the center E , on the instrument where the spirall line is on the same , Tab. XX. Fig. 1.

In the time of obseruation by the Inclinatory-ring , before described , marke what degree in the ring the Inclinatory-needle pointeth at in the meridian circle of the same , then in this instrument here described , note the degree obserued in the ring vpon the moueable quadrant from B to C , and turne this quadrant about till that this note or degree doth touch the spirall line ; here stay the moueable quadrant , & his index C A will shew in the quadrant D B , the altitude of the pole in that place .

So back wayes set the index of the moueable quadrant to any eleuation of the pole , and where the spirall line cutteth the limbe of the moueable quadrant , the degrees and parts shew what should be the number , due to the angle of the Inclinatory-needle , and what parts he would point out in that place . A Table of the inclination of the needle , answering to euery eleuation of the pole , might be made by this instrument .

CHAP. XXXIX

Of finding the needles inclination in euery latitude by Table .

THe way to find the angle , which the Inclinatory-needle maketh with the horizon in any latitude , or the degrees correspondent , by a table , is most profitable and ready , because that knowing any one of these two , that is , either the altitude of the pole , or the angle of inclination to the horizon , the other is presently knowne by the table .

Seeke in this Table following the altitude of the pole in the left collumne , and in the next place towards the right hand you shall find the degrees and minutes of the needles inclination , vnto the horizon , answerable for that latitude ; as for example . I would know what would be the arch of the angle of the Inclinatory-needle where the pole is eleuated 60 degrees , I to R make the angle S R N to consist of 52 degrees and 12l , which being subducted from the angle of E R N , containing 63 deg. and 17l , the angle S R E will retaine onely 11 degrees and 5l , whose complement S R T consisteth of 78 deg. and 55l , declaring the inclination of the Magneticall needle vnto the horizon R T , where the latitude of the place is 60 degrees .

CHAP. XXXX .

Of finding the angle of Inclination , the Magneticall meridian , and the Azimuth together .

IT is very conuenient at sea to haue a large Inclinatory-ring with his Magneticall needle of a foote diamiter , that the diuisions of the meridian circle being large , the degree of the mouing needle will the better be perceiued , and to haue a waight of diuerse pounds fastned at the bottome to hold this ring plumbe and steady : moreouer on this waight I would haue a compasse , or directory-needle placed in his bottome , and a beame for a diamiter and semidiamiter of brasse , before described , for the obseruing of the Magneticall azimuth , as was appointed in finding the variation of the Compasse .

diagrams

A long wier that hath bene excited Magnetically , being thrust through a corke , and placed in the water , will shew the Inclination and Magneticall meridian , at one instant , in his quiet situation .

CHAP. XXXXI .

Inclinatory-Needle .

THe Earth being a Magneticall body and globe , conformeth the Inclinatory-needle to certaine angles of inclination in euery latitude of the pole , which angles are alwayes one and the same in euery paralell , as hath bene demonstrated in diuerse Chapters .

Both by the Load-stone it selfe , by the fundamentall hypothesis , by instruments , and by tables ; but because that the globe Magneticall of the Earth hath many cauities filled with other substances different from Magneticall nature , and many mountaines Magneticall mounted aboue these substances higher and lower , so that some attract , being aboue the point of the Inclinatory-needle , some being vnder it ; some placed before it , draw the point of the Inclinatory-needle vp vnto them , other behind it , beeing also adamantiue forts will haue this Inclinatory-needle strike saile to them also , by which meanes the naturall conformity of the Inclinatory-needle to his naturall angles is much disturbed and depraued , whereby it commeth to passe that this needle hath his variation also , as well as the directory needle hath , as is before demonstrated .

Therefore the variation of the Inclinatory-needle is , when in one altitude of the pole this needle pointeth out another angle , different from the true and respondent angle of that latitude of the pole , being hindred by a mountaine , or part Magneticall , that doth attract one of the points of the Inclinatory-needle , approching neere vnto it , either neere the poles or aequator , in so much that the angle of inclination is made lesse or more then it naturally would be .

In sailing East or West vpon a paralell , hauing hie land on the side towards the pole , consisting of Magneticall substance , this will attract the Inclinatory-needle , and cause his naturall position to be more perpendicular then it would be .

If the shore about the pole be situated betweene the Inclinatory-needle and the aequator , this adamantine eminency will attract the needle vnto it , making his inclination lesse plumbe then naturally it is .

In sailing East or West neerer the aequinoctiall , where the cariage of the Inclinatory-needle is lesse perpendicular , and more tending to the leuell with the horizon , the Magneticall eminency betweene the pole and the needle , will pull downe the higher end of the same , and make him more paralell to the axis of the earth , then naturally he could endure .

Euen so an adamantine mountaine , betweene the Inclinatory-needle and the aequinoctiall line , will lift vp the lower end of this needle , being within the Magneticall vigor of that mountaine , and make him more paralell with the horizon then his naturall conformity requireth in that paralell .

The variation of the Inclinatory-needle is greater in the parts neerer the aequinoctiall , then it is in the parts neere the poles , where this needle is not attracted so many degrees from his naturall angle , as vsually he is neere the aequinoctiall .

If in the parts neere the poles , the Inclinatory-needle be caried betweene two eminences Magneticall , in that space of the straight where both their vigors be of like validity , they will make the application of this needle perpendicular , crossing them both at all right angles , not much vnlike , as it is in XV. Chapter of applications , Table VIII . Fig. 1 .

In sailing neerer the aequinoctiall in straights betweene two adamantine mountaines , whose vigour attractiue surpasse the generall vertue disponent of the Magneticall globe of the earth , these will lay the Inclinatory-needle in a paralell and leuell to the horizon , though they be many degrees from the aequinoctiall , as Chapter XV. Tab VIII . Fig. 2.

Lastly , in passing or sailing neere and ouer a vigorous Magneticall rocke , in the sea , or earth , vnder vs , in approching neerer vnto it , the same will attract the Inclinatory-needle from his right place , and comming neerer the rocke , it will alter him much more , and passing ouer the same , it will attract the needle perpendicularly , and being past , this needle will be freed by little and little from that disturbance of his naturall inclination .

These varieties are found vpon the Magneticall globe or Terrella , by hauing a conuenient peece , or peeces of iron placed thereon , as hath bene sayd , and placing the Inclinatory-needles , before described in the II. chapter , the one of them put vpon a Lute-string , the other in his frame , Tab. II. Fig. 17. 18 or 19. so that I hope I need not set downe any types hereof , for the ingenious will better conceiue how to gather this matter from the globe of the Loadstone , then I can possibly explaine in many troublesome figures , or the workeman deliniat by his skill vnto you in printed tables and figures .

CHAP. XXXXII.

Inclinatory-needle .

HAuing declared the manifold causes of the variation of the Inclinatory-needle from his true and naturall angle of inclination with the horizon ; it followeth that we deliuer plainely how to discerne these euents when they shall fall out , which are known perfectly by hauing the true eleuation of the pole , where these matters shall be required .

The rules and wayes how to know the eleuation of the pole in all places , is so perfectly set out by most Astronomers and writers of Nauigation , and so well knowne to all expert Pilots , that it is a thing needlesse here to repeate them .

Besides the ingenious Pilot knowing the eleuation of the pole in some places of his voyage that he hath passed , by keeping a true , not a dead reckoning of his course in pricking his Card aright , and obseruing the way with the logge-line , with other currants and occurrants , will giue a very artificiall coniecture of the eleuation of the pole in that place where he is , though he see neither Sunne nor Starres .

Notwithstanding because the skilfull Pilots may be hindred in this kind of obseruation , by the falling of the ship to Lee-wards , and by other extraordinary change of weather , and other disturbances that may many wayes fall out at sea , therefore I will onely remember one way out of the principals before deliuered , whereby he may at any time of the day , the Sunne shining , know the altitude of the pole .

This thing is chiefly performed by knowing the true variation of the Compasse , which sheweth the true meridian for that place , presently seeke out the true Azimuth also , which is perfectly knowne by the shadow of the Sunne vpon the limbe of the Compasse , by the furniture of the beame , before described , instantly take the altitude of the Sunne by the Iacobs staffe at sea , or a large quadrant at land .

The true Azimuth and Almicanter thus knowne , seeke the point where they crosse the one the other in the Rete of the Mathematicall Iewell and Astrolabium Catholicum , then obseruing the paralell of the Sunnes declination for that day , turne about the Rete of this instrument , vntill this paralell of the Sunnes declination be touched by the point , where these two circles of altitude and position meete , and then the horizon of the Rete will shew in the limbe the latitude of that place .

The latitude of the pole for any place being knowne , the true angle of the Inclinatory-needle is manifest and apparant , as it is set downe and knowne by the XIII . chapter , in the chapter to know the angles of inclination by the instrument , and in the table of the degrees of the Inclinatory-needle , answerable to euery eleuation of the pole .

Now obserue the degrees that the Inclinatory-needle pointeth out in his ring in that place , and take the difference of these from the degrees of the true angle , and that is the variation of the Inclinatory-needle for that place .

CHAP. XXXXIII .

Of finding the Longitude .

HEre I purposed to haue ended this short Treatise of Magneticall matters , but because that this thing is not altogether impertinent thereunto , I thought it not superfluous to annex this little chapter of finding the longitude , for although that the Magneticall needles , before treated of , do not shew the longitude ; yet because the true meridian and altitude of the pole is knowne by them , there is much helpe brought thereby for the knowledge of the longitude , which by a few easie obseruations more , from the body of the Moone , will be obtained , whose motion if it should be set downe and ordered in an exact manner , would require a large discourse , with many rules and obseruations of the Moones inequality of motion , anomaly and prostapherisis , of his excentricity , paralaxis , with the varietie of his latitude and nodes , which thing , being very laborious and curious , shall be here omitted , referring you herein to Tycho Brahe and his rules , and onely I shall here set downe rules to know the place of the Moone at a larger scantling , yet very neere the truth ( though not the truth it selfe , which peraduenture the best Studied in this kind can very hardly do ) only borrowing halfe a dayes motion at the Moone , wherein the matters before mentioned will not alter many minutes .

Prouide an Almanake or Ephemerides for any place or port , wherein the apparent place of the Moone in the Zodiacke is exactly set downe in degrees and minutes for the noone of euery day , especially of the day of obseruing , then take the difference of the Moones motion from the day before , and reduce it into minutes , deuiding them by 24 houres , the quotient will shew what minutes the Moone moueth in an howre .

Now take the altitude of the Moone at any time of the day or night by the Iacobs staffe , or a quadrant , then obserue the Azimuth of the Moone by shadow , ( as before for the Sunne ) or by a ruler with sights , which if it do differ any howers from the meridian , alow the parts due of the Moones motion .

Then seeke in the R●te of the Mathematicall Iewell , or Vniuersall Astrolabe , where the Azimuth and Almicantaraph of the Moone , newly obserued , cut each other , setting the horizon to the altitude of the pole , and looke what paralell doth cut these two , and follow the same vnto the Eclipticke line ( or do 〈◊〉 like of the Moones latitude ) in that signe , degree , and minute of the Zodiacke , the Moone is in at that instant .

These degrees , fewer or more then those of the radicall and fixt meridian , for which the Ephimerides was made , do shew what howres and parts are to be added , if the obseruation be towards the West , or substracted if in the East , to this meridian ( it is to be noted that euery hower containeth 15 degrees of the Equinoctiall ) and thus the longitude of that place you are in , will be attained , which you desire .

But to find the longitude of any place you go to , from the place you passe from , by these Magneticall-needles onely , it will be necessary to pricke your Card as well by the degrees of latitude of the pole , correspondent to the angles of the Inclinatory-needle , as by the way the ship maketh vpon the points of the Directory compasse , and therefore it will be fit to haue both these needles placed together as in the type of the XL. Chapter , and pendant before the Mariner at the helme with the Compasse and Trauers-boords for them both .

Now for this purpose I would haue another Trauers ruler or limbe for the quadrant of the Inclinatory-ring , placed before him , as it is described in the Page following , where there is only 30 degrees deuided vpon the same , which being twice more repeated , will make vp 90 degrees , euery degree hath 6 hol●● , for pegs to be put into them , for the number of 10 minutes apeece , and on the first columne on the left hand there are 4 holes made to receiue pegges according to the number of howers you saile on such a degree and minute , pointed in the Inclinatory-ring .

diagram

If any errors should chance to fall out by any variations of either needle , then at any time when the Sun doth shine they may be amended by the precepts already largely deliuered in that case of either , both in many Chapters of this booke , and in the last precedent Chapter .

CHAP. XXXXIIII .

Of the matter of the Magneticall globe of the earth by the Needle .

AT length we haue brought our short Treatise Magneticall principally & most profitably to declare the nature of the Directory and Inclinatory-needle , both towards the Terrella and Semiterrella , and towards the Magneticall globe of the earth , and how the proportions and similitude of their applications and conformities to both are alike and the same .

Onely the Magneticall-needle being of a saeminine and sequent substance , as hath bene demonstrated in the VIII . XXI . and XXII . Chapters , doth behold the round Magnet , and the round Iron , with that point that is of the same nature and demonstration that the pole is , which he followeth and affecteth , contrary to the nature Magneticall , that is in the Adamants themselues , one towards the other , or of the needles one towards the other .

But this Magneticall-needle being freed from the Magneticall orbe of the Loadstone and Iron , will haue that point of the needle that followed them directed by the vertue Magneticall of the earth into a contrary prouince of polar preheminence .

For the Magneticall-needle doth conforme it selfe vnto the Earth in the same fashion that the Adamant and Loadstone it selfe doth ; neither is it so seruiceable vnto the Magneticall globe of the earth as he is vnto the Magnet and Iron , but is of a fellow-like species with the earth , as well as the Adamants themselues are .

Whereby I do gather that the matter of the interior parts of the Magneticall globe of the earth is not the same with these we know of the Loadstone and iron , into whose bowels neuer any man , by the deepest mines , or other passages of fissurs and cauities , made by great Earth-quakes , euer yet descended to shew vnto vs any part of the earths interior substance Magneticall , and though I take the matter of the bowels of the earth to be Magnetical , yet the application of this Magneticall-needle demonstrateth , that the Magnetical globe of the earths inward substance consisteth neither of sollid Load stone , nor of iron-like mine or clay or such like materials , as they which haue thought themselues most skilfull in Magneticall Philosophy haue imagined .

For if the Magneticall globe of the earth were of any Iron-like substance , then that point of the needle that affecteth a polar iurisdiction , placed neere the Loadstone and the iron , would also , being applied vnto the earth , behold the same prouince and iurisdiction polar , being directed by the vigor of the earths Magneticall orbe of like nature ; but this is not so , as all confesse and may proue .

Therefore I hold that the great Magnetical globe of the earth consisteth of a Magneticall substance vnknowne vnto vs , as also the bodies of the Magneticall globe of the Moone and of the rest do ; and so conclude that the workes of God are most wonderfull , and altogether past finding out .

But here before I end , I am to satisfie that I made promise of in the XII . Chapter , that I would shew my conceipt of the reason why the needle in his passage from the aequator of the Magnet by the pole , to the aequator againe , should make the circumuolution of an whole circle in turning about his foote , hauing passed a semicircle of the Terrella or Semiterrella , and would make another whole circle about the other semicircle of contrary nature with his other point .

For to cleere this with the nature of the two prouinces , which is aduerse one vnto the other . I would wish that you would conceiue and propound two globes of Magneticall nature and substance , as tender as clay , the one of them to be animated with the North and articke vertue at both poles , as Tab. XX. Fig. 3. aa , to turne to the North onely : and the other globe , with his poles Tab. XX. Fig. 3. bb to be endowed with the antarticke power to moue to the South onely .

Now if the globe of the earth , or of the Magnet-stone were made onely of one of these globes , then there would be a strife betweene the poles of one of the globes , which should behold his peculiar point , as if the pole a of the North vertue should behold the North ; the other pole a of the same globe , being of articke nature , would also striue to behold the North , or at least in their equality of power would rather respect East and West , so that there would be no stability by the poles of such kind of globes .

Therefore the skilfull Potter , who made the earth