M. Blundevile his exercises containing sixe treatises, the titles wherof are set down in the next printed page: which treatises are verie necessarie to be read and learned of all yoong gentlemen that haue not bene exercised in such disciplines, and yet are desirous to haue knowledge as well in cosmographie, astronomie, and geographie, as also in the arte of navigation ... To the furtherance of which arte of navigation, the said M. Blundevile speciallie wrote the said treatises and of meere good will doth dedicate the same to all the young gentlemen of this realme.

Of the Mariners Ring or Astrolabe, and of his crosse staffe. Chapter. 12

NOw according to the order set down in the beginning of this Treatise, I must néeds speak somewhat of the common Marmers Ring or Astrolabe, and of his crosse staffe which serue not to so many purposes as that of Stofflerus or of M. Blagraue before described, but onlie to take the altitude of the Sunne, or of any Starre or Planet, nei∣ther are so many conclusions to bee wrought by their common crosse staffe as by that of Gemma Frisius, or by that which Master Hood hath latelie inuented. Sith our Marmers for the most part doe vse their common crosse staffe to none other ende but ey∣ther to take the altitude of the Sun or of any fixed star or planet, or els to take the distance betwixt two stars, the making of which staffe is plainly set downe by Martin Cortes in his arte of Naui∣gation, and also the making of their Astrolabe.

But Cogniet and Wagoner do set downe a new kind of Crosse staffe, hauing 3. transoms or crosses euery one lōger & shorter than another by the one halfe, affirming that so many conclusions may be wrought therby as by that of Gēma Frisius, but in mine opiniō they are not to be cōpared in al respects to that of Gemma Frisius which though by reason that the yard therof is of so great a length

as it is not maniable in a shippe, yet vpon the land it is most ser∣viceable, nor yet to that of Maister Hoods inuention, which is most maniable, and therwith verie light of carriage, by whose staffe I thinke verilie that as many things may be wrought as by anie other kind of crosse staffe whatsoeuer, and with lesse trouble, yea, and in matters of Astronomie more trulie by reason that the yard and transome be of one selfe length, and thereby the degrées bée larger throughout the whole quadrant than they be in the common crosse staues, for in them the degrées from 50. vpwards to 90. are verie small and haue narrower spaces than M. Hoods staffe hath. Againe, whereas in vsing the Mariners crosse staffe in such lati∣tude, as the Sunnes beames be of great force, they are faine to haue glasses made of purpose to saue their sight, and in some pla∣ces all too little. But in vsing M. Hoods staffe they shall not néed to behold the Sunne it selfe at all, but onely to marke vpon what degrée of the yard the shadow of the Vane stréeketh. Moreouer, when the Sunne or starre is 50. or 60. degrées high, they are fain to vse their Astrolabe and not their staffe, which Astrolabe in mine opinion, as I haue said before, is the best instrument of all others to take the altitude of the Sunne in the day, or of any starre in the night, and because I haue here commended vnto you M. Hoods staffe, I will first set downe a plaine description thereof together with those few Astronomicall vses which do chieflie belong to the Mariner, without committing anie offence I hope to the author thereof, and then I will describe vnto you the Mariners ring and his common staffe together with the vses of the same.

But as I was about to describe vnto you M. Hoods staffe, a friende of mine comming in the meane time desired mée that I woulde first set downe the making and vse of the crosse staffe with thrée transomes, which Wagoner and Michaell Cogniet doe so much commend, and as I heare, is vsed of manie sea men in these daies, whose request I could not well denie, and therfore loe here followeth both the making and vse thereof.

Of the crosse staffe hauing three Transames or Cursours, commonly vsed in these dayes, the vse and making whereof doth hereafter followe according to the description of Wago∣ner and Michaell Cogniet.

FIrst prepare a right staffe of firme woode that is square euery way, bearing in thicknes thrée quar∣ters of an inch, and in length thrée or foure foote, for which you must also prepare thrée Transames or Cursours euery one shorter then another by the one halfe, for the longest would containe in length twelue inches, the seconde sixe inches, and the shortest or least thrée inches. And euery one of these Transames or Cur∣sours must be cut with a square hole in the very middest, so as they may be made to runne iust vpon the staffe to and fro, these things being prepared, you must deuide thrée sides of the staffe into cer∣taine degrées to serue the thrée seuerall cursours as followeth.

First you must vpon a smooth square Table somewhat longer euery way then the staffe, and for want of one such Table you may ioyne two Tables that may stand eauen together, drawe by helpe of a true long squire a right Triangle marked with the let∣ters A. B. C. and let A. be the right Angle, and the Centre as you sée in the figure following, and let both the sides of the saide Triangle be of like length to your staffe, then putting the one foote of your compasse in the Centre A. and the other foote in B. or C. drawe a quarter of a circle from C. to B. and hauing deui∣ded that quarter into two equall partes, make a pricke in the middest marked with the letter D. and laying your ruler to that pricke and to the Centre A. drawe a right line which shall be A. D. then deuide the halfe Quadrant D. B. into nine equall partes making 90. equall degrées procéeding from B. to D. so as the first degrée may be at B. and the 90 at D. that done, take with your compasse the iust halfe of the longest Transame, and kée∣ping your compasse at that widenesse, set the one foote in the Cen∣tre A. and the other foote in the line A. C. so farre as that wide∣nesse will extende, and there make a pricke marked with the let∣ter E. then from that point drawe a right line that may be a Pa∣rallell

to the line A. B. which line shall be E. F. then take with your compasse the halfe of the middle Transame, and kéeping your compasse at that widenesse, set the one foote in A. and the other foote in the line A. C. so farre as that widenesse doth extend and there make a pricke marked with the letter G. and from that pricke drawe a right line that may be a Parallell to A. B which line shall be G. H. Thirdly take the one halfe of the least Tran∣same with your compasse and transferre that widenesse to the line A. C. setting the one foote of your compasse in A. and make a pricke with the other foote in the line A. C. as before, marked with the letter I. and from that pricke drawe another right line that may be a Parallell to the line A. B. which shall be the line I. K. Now to graduate the first side of your staffe to serue the longest Transame, you must lay the ruler to the centre A. and drawe right lines from thence to euery degrée of the circumfe∣rence contained betwixt 90. and 30. and those lines shall deuide the line E. F. into so many vnequall spaces as doe belong to the first side of the staffe, for you must lay the first side of the staffe to that line to be marked according to the diuision of that line, the neather section whereof towardes the lower ende of the staffe must be marked with 90. and the vpper section with 30. so is the first side of your staffe truely deuided to serue the longest Tran∣same, now to serue the middle Transame you must deuide the line G. H. by drawing right lines from the Centre A. to euerie degrée of the circumference contained betwixt 30. and 10. which lines will deuide the line G. H. into vnequall spaces, of which spaces the lowest must be marked with 30. and the highest with tenne, according to which diuisions you must marke the seconde side of your staffe by laying the side close to the line G. H. so shall that side be marked to serue the middle Transame, then lay your ruler againe to the Centre A. and drawe right lines to euery degrée of the circumference contained betwixt 10. and the first or second degrée next to B. and those lines shall deuide the line I. K. into vnequall spaces, the lowest whereof is to be mar∣ked with 10. and the highest with 2. or 5. according as your instrument will beare, and according to those sections you must deuide the thirde side of your staffe by laying the same close to that saide line I. K. and remember to make your lines of diui∣sion

so finely as is possible, so shall your staffe be the more truely graduated. And noce that in graduating your staffe, you shall not néede to drawe right lines from the Centre to euery degrée of the circumference contayned betwixt the 90. degrée and the 60. degrée, for when the sunne or any starre is higher then 60. degrées, you must vse your Astrolabe and not your staffe which will not serue you to looke so right vp to take so great an altitude eyther of sunne or starre.

[illustration]

A figure of the foresaide Triangle.

[illustration]

The shape of the staffe with his three Transames, together with the vse thereof.

Whensoeuer you would take the Altitude of the Sunne or of anie starre, you haue first to consider whether the sunne or starre be 30. degrées or more high: for then you must place the longest Transame vppon your Staffe. And set the lower end of your staffe marked with ninetie to your eye, which is al∣wayes to be done howe high or lowe so euer the sunne or starre be, and you must mooue the Transame ey∣ther forwarde or backewarde vn∣till you may sée by the vpper ende of the Transame the bodie or mid∣dest of the sunne or starre, and with the neather ende of the Transame the Horizon, and then looke in what degrée the Transame cutteth the staffe, for that is the Altitude of the Sunne and starre at that present, but if the sunne be not 30. degrées high, then you must put on the mid∣dle Transame, and if hee bée lesse then tenne degrées high, you must put on the shortest Transame, and thē do as before. Thus much touch∣ing the Crosse staffe with 3. Tran∣sames, nowe I will describe vnto you Maister Hood his staffe, and shew you the vse thereof.