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 Râ—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 coÌ„taineth 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 holâ—â— 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 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 maÌ„ 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 coÌ„sisteth 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 TAM ROBVR TAM ROBOR NI-COLIS ARBOR IOVIS 1610 N O LONDON Printed by Nicholas Okes dwelling neere Holborne-bridge at the signe of the Hand 1613.
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 VVHen 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
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 feateth 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
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 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
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. Of finding the variation of the 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