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.

How to make with you Compasses, a perpendicular line to fal from any point giuen vpon another right line, making ther∣with right angles without the helpe of any squire.

SEt the firme foot of your Compasse in the point giuen, and extend the o∣ther foote a little beyond the line right against the point gi∣uen, & draw a secret Arch or por∣tion of a Circle that may cut the said liue in two points, and deuide that part of the Arch which lieth betwixt the two sections into two equall parts, setting a pricke in the very midst therof: then hauing laid your ruler to that pricke, and also to the point giuen, draw a right line, & that line wil fall vpon the other line with right Angles, as you may sée by this figure.

[illustration]

The Table of miles answerable to one degree of euery seuerall Latitude.

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

Though it be the common order of working to know by helpe of the former table, the distance of two places differing onely in Longitude, yet I thinke it a more sure way to find it out per Ta∣bulas Sinuum, the rule whereof is thus.

First take the difference of the two Longitudes, by subtrac∣ting the lesser out of the greater, and the halfe of that shall be the Arch which you haue to séeke in the front of the Tables, then mul∣tiply the sine of that Arch by the sine of the complement of the common Latitude, and deuide the product thereof by the totall sine, the quotient whereof you must séeke out in the Tables a∣mongest the sines, and the Arch of that sine is the one halfe of the distance, which being doubled shall be the whole distance contay∣ning degrées of the great Circle, and euery such degrée contay∣neth of Italian miles 60. and of German miles 15. and by wor∣king thus you shall finde the distance betwixt Compostella and Constantinople to be 1846. Italian miles, supposing the com∣mon latitude to be 43. degrées, and the difference of their longi∣tudes to be 42. degrées 30′· And by working by the common ta∣ble you shall find the distance of those two places to be 1827. Ita∣lian miles as before, because the common Table hath no minutes of miles but onely seconds, which are not to be accounted of, & in working by Appian his Table hauing minutes of miles, you shal find the said distance to be 2184. Italian miles, and by Mercator his Map to be 1980. Italian miles, in whose Map the common Latitude of the said 2. places is 43. & the difference of their lon∣gitudes is 44. 0′· And by the skale set down in Plancius his Map, you shal find the distance to be 2520. Italian miles, in which Map the cōmon Latitude of the two foresaid places is 42. deg. 30′· and the difference of their Longitudes is also 42. degrées 30′· Truely I must néedes confesse that it is not so easie to make a skale or trunke for a Mappe or a Carde drawne in plano, as for that which is drawne vpon a round bodie or Globe: and therefore it is no maruaile though the skales of Mappes drawne in plano, and likewise the trunkes set downe in the Mariners Cardes doe not alwayes shewe the true distance of places, which I beléeue is to bee done as truely and a great deale more readily by my friend Maister Wright his Semicircle before described, then by the rules of Gasparus Peucerus in his booke de dimensione ter∣rae,

which rules doe depend vpon the knowledge of the quantitie of the Angles and sides of Sphericall Triangles, which kinde of working is indéede more troublesome and tedious then readie or pleasant. But if Maister Wright would make his Demicir∣cle an vniuersall instrument to find out thereby all the thrée kinds of distances as he promised me to doe, there were no way in mine opinion worthie to be compared vnto it, neither for the truenesse, easinesse, nor readinesse of working thereby.