HAuing dedicated this litle Booke to the Right Hon. the Lord high Admirall of England , to whom the gouernement of sea causes next vnder her Maiestie chiefly appertaineth ( with whom also it hath found such fauourable acceptation as of so honorable a personage might be iustly expected ) I thought it meete in the next place to commend the same to your Wor. societie also , as to them who haue best occasion in your so manifold nauigations to make most plentifull and sufficient triall thereof , and to whom it may assuredly doe most necessary and profitable seruice . But least you should stand in doubt of this my commendation , the Right Honourable Count Maurice , Lord high Admirall of the vnited Prouinces of the Low Countries , hath not only commended the same to all Masters of ships and their companies ( or brotherhoods as we may call them ) that are vnder his iurisdiction ; but hath also commanded them to make diligent and continuall obseruation in all their voyages , according to the directions prescribed herein . He also , as not content that the fruit which may spring here of should be conteined within the narrow boundes and compasse of the Lowe Countries , hath caused this booke to be translated into the French and Latine tongues : endeuouring as it may seeme hereby to make the same knowen to all nations in Christendome . Amongst whom as the Latine translatour M. Hugo de Groot hath chosen the Venctians for their excellencie in Nauigation ( as he conceiueth ) to whom he might especially dedicate this small Volume togither with his owne labour in translating the same : So I thought it meete to make choise of your worshipfull society , whom I take to be nothing at all inferiour to the Venetians either for excellencie of skill , or for vse and experience in that facultie : and to whom I may more iustly commend this little Booke , euen almost with the same words which Hugo de Groot vseth to the Venetians as followeth .

Therefore that we may enter a little more deepely into the matter , Aristotle the wittiest of all philosophers and the most famous Lawyers doe witnesse that all arts were founde , out of the necessitie of mans nature , that what is wanting in one , might be supplied by that which is abounding in another : and that because euery countrey yeeldeth not all things , there might be a mutual exchange of one thing for another by way of merchandise . But now because diuerse countries are very far distant each from other , that there can be no carriage of any wares or marchandise from the one to the other , either on beasts backs or in cartes : the art of Nauigation was therefore inuented , that the sea might supply the want of dry land . Yet surely skilfull nature hath done all this in vaine , if a certaine way how to sayle cannot in some sort be found , but that mariners must be constrained to make their voyages doubtfully not knowing what course to keepe . Therefore the ancient nauigators ( thinking not without cause that there was great affinitie betweene Astronomie and Nauigation ) directed all their course by the starres , the Sidonians by the lesser beare which is the certainer , the Grecians by the greater which is the clearer . But because neither star truely shewed the North part of the world , they were oftentimes deceiued in their coniectures : and because the night is not alwayes so cleare that those starres may be seene , if the skie were at any time ouercast they had no meanes wherby they might know which way they ought to guide themselues . Hereof it commeth that in ancient authors oftentimes , & in many places we see the mariners complaining of the darknesse of the nights , and that the greatest and most famous nauies haue beene dispersed and discomfited , by reason of the vncertaintie of these things .

But assuredly it seemeth to be so ordeined by nature , that all things should not be brought to light at one time : but that after a long continuance of times the certaintie of things should be knowen . There is a stone which for the exceeding great strength thereof is called Herculeus , that is the stone of Hercules , & because it draweth iron vnto it , is by the Grecians called 〈◊〉 〈◊〉 〈◊〉 〈◊〉 〈◊〉 , commonly it is called by the name of him that first found it , Magnes , that is the Magnete or Load-stone . For it appeareth out of Nicander and Plinie , that one Magnes found it sticking to a sharpe pointed piece of yron . After a great number of yeeres a new propertie of that stone was reueiled , that being rubbed vpon yron , or rather vpon steele , it would make the same point to the North. Therefore when by this marueilous pointing the mariners knew the North , and ouer against it the South , and making account by the eleuation of the pole they learned also the latitude : then they had ( as it was thought ) means sufficient of infallible direction how to guide themselues at all times . But neither did this ioy ( as many times it commeth to passe ) continue long . For when they sayled from the East westwards , the Loadstone was found by litle and litle to decline from the North ; which thing strooke no small doubtfulnesse and vncertaintie into the mariners mindes . Yet nowe at the length , by long obseruation of the declinations of the loadstone that haue bene diligently sought out in diuerse places and times , the matter is brought to that issue , that they which are most skilfull in the Mathematicks , and amongst them the said Count Maurice of Nassau , haue supposed that this declination of the Loadstone happeneth not by chance , but is caused by some certaine reason in nature , that according to the varietie of places the pointing of the needle should also varie .

Wherefore the said Count Maurice sent this exhortatorie iniunction ( for so I may call this litle booke written by his Mathematician Steuinius ) to them that take charge of ships , that if these things were not found in all points to be so as his obseruation importeth , they should do so much as in them lay , that out of diuerse experiments some certaine reason and rule of the variation might be gathered : which if it may by diligent obseruation be obteined , then there shall not onely be a more certaine way to knowe the course from place to place by the instrument made to finde the variation ( of which way more shall be spoken in the booke it selfe ) but the longitude also , or rather the effect of the longitude shall be giuen by the variation ; which thing also shal be shewed more at large in the Treatise it selfe following . Because therefore it is certaine that this knowledge cannot otherwise be found but by the experiments of diuers men compared togither , and that by diuers obseruations a more easie way may be prepared for science ( which from the particulars ariseth vp vnto the vniuersall ) I thought good to present vnto you this iniunction of the worthy Count Maurice , that if you ( which are most expert in Nauigation ) be of opinion that there may be so great profite of this matter as we ( which thinke it to appertaine to the principall state of the common-wealth ) you might doe your best endeuour vnto what place soeuer you shall come ( taking with you needfull instruments for that purpose ) to obserue diligently the variation of the magneticall needle , that at length we may come to that certaintie , that they which take charge of ships may know in their nauigations to what latitude and to what variation ( which shall serue in stead of the longitude not yet found ) they ought to bring themselues , that by this meanes they may assuredly finde what place soeuer they will in the midst of the maine Ocean sea . And although this bee the end for which principally this Booke was made , notwithstanding we make no doubt that there may many more be found no lesse profitable then this ; of which sort is that which wee of late haue found , which may also be of very great profit vnto vs : To wit , that when any nauie ( for which cause our common-wealth hath obteyned exceeding great renowne ) is prepared against the enemie , a certaine place may be appointed in the midst of the sea , into which ( if perchance too great a force should come vpon them vnlooked for ) all the ships after a certaine time might assemble themselues . Whereto I may also adioyne a third vse of the variation , that is , the reforming of many errors which must needes be in the ordinarie sea-charts , because the coasts of all countries and the courses from place to place , haue beene set downe in them by direction of the varying compasse , without abatement or allowance answerable to the variation ; wherof there must needes follow much deformitie and confusion in many parts of the chart , especially where the variation is great , as it is vpon the coast of Newfoundland ; where the variation being two whole points of the compasse ( as it is reported ) there must needes be so much error also in laying out all the sea coast of that countrey , and in the courses of all places neere adioyning in the ordinarie sea charts . All which errors may be amended , if the variations be first truely obserued , and then abated from , or allowed to the courses of all places , as neede shall require .

But the variation cannot serue to so great vse as otherwise it might , except other errors also aswell in the chart , as in other instruments and meanes of nauigation be also auoyded . For the chart as it hath beene hitherto generally made with right-lined rumbes and degrees of latitude euery where equall , must needes be very erroneous , especially in the Northerne parts thereof , that although all the foresaid errors arising by the variation were corrected , yet for this cause onely you may bee deceiued one , two , yea three whole points of the compasse , in the courses of many places : and in measuring the distance you may erre one halfe , yea three quarters and more sometimes , accounting the same to be twise , yea thrise greater then indeede it is , especially in farre Northerly nauigations . If therefore these so notorious errors be not also amended , the correction of the errors arising by the variation , cannot be to so great purpose as otherwise it might .

Neither can that be so fully performed which in the Treatise following is chiefly intended ( that is , to find any place at sea by the variation and latitude ) except the meanes that haue beene vsed for finding the latitude be also amended . For in obseruing the heigth of the sunne and starres , with the small crosse-staues which are most vsuall for that purpose , there may be error of halfe a degree , and more sometimes by neglect of the parallax or eccentricity of the obseruers eye . The Regiments or Tables of declination of the sunne that haue bene most commonly vsed by English mariners doe erre oft times ten , eleuen , or twelue minutes . The rule of allowances and abatements to be added to , or subtracted from the heigth of the pole-starre for finding the heigth of the pole ( being grounded vpon a false position , to wit , that the pole-starre is three degrees and an halfe distant from the pole , when indeede it is almost 40 minutes lesse ) must needes be false many times more then halfe a degree .

The declinations of the principall fixed starres as they are set downe in the bookes of Nauigation , that haue bene heretofore published , are for the most part erroneous ; many of them differing from trueth aboue halfe a degree , & some of them an whole degree , yea two whole degrees and more . All which imperfections of so excellent an art , I haue since the time of my first employment at sea ( now more then tenne yeeres since ) by diligent search with no small labour discouered and amended , not onely by tenne whole moneths experience at sea , but also by often and diligent obseruation on land , as it may more at large appeare in my booke of errors in Nauigation ( which at mine own charges is also published for the common good of you all ) wherein the way is shewed how your charts and crossestaues may be freed from the errors aforesaid ; and the declinations of the sunne and fixed starres are set foorth vnto you , agreeably to the trueth of the heauens found out by often and exact obseruations , whereby the latitudes of places may be found much more truely then hath beene accustomed . This Booke therefore , because it may affoord needfull ayd for accomplishing the sayd renowmed Count Maurice his desire in finding the latitude more exactly , and may also deliuer you from much inconuenience and daunger , which may necessarily be expected to follow out of so many and notable errors as hitherto haue beene in the vsuall meanes of Nauigation alreadie mentioned : I commend the same togither with this small Treatise now following vnto you all , to be dayly tried and examined by the touchstone of your long and skilfull experience at sea : nothing doubting but as they haue endured the more exquisite triall of exact obseruation , and Geometricall demonstration both by seamen and landmen on shore , so they shall be found agreeable to the heedefull experiments of all skilfull Nauigators at sea . And so with my whole heart commending you all to him whose worde both seas and windes obey , I end .