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 know the way of your ship, and how many leagues are to be counted for one degree of Latitude in euerie Rombe whereby you sayle. Chap. 32.

FIrst you haue to vnderstande that in saylinge iust North and South, you do alwayes abide vn∣der one selfe great Circle called the Meridian, vnder the which, when you haue sayled so farre as the altitude of the Pole is changed one degrée, then haue you gone 17. Spanish leagues, and a halfe, and you haue to note that euery Spanish league containeth 2857. fathams, and that our English league containeth no more but 2500. fathams, so as the Spanish league is more then our English league by 357. fathams, & euery fatham containeth vi. foote. Againe in sayling East and West, you do alwayes remaine vnder one selfe Parallell, by meanes whereof the altitude of the

Pole doth neuer alter, and therefore no true account can be made of the leagues, but by such meanes as Cogniet teacheth in the Chapter following. But if in sayling North and South, you de∣cline one rombe either towards the East or West, and go so farre as the altitude of the Pole is changed by one degrée, then you haue made somewhat more then 17. Spanish leagues and a halfe, and to be short, the more rombes that you decline towardes the East or West, the more leagues in number doe belong to one de∣grée of altitude, as you may plainely sée by this figure demonstra∣tiue here following in which the letter A. signifieth the place or point in the Card, from which you depart situated in the Parallel A. B.

[illustration]

Then suppose C. D. to be another Parallell equally distant from A. B. by one degrée of altitude. Now if you saile right East or West, then you shall alwayes remaine in the Parallel A. B. equally distant from the Pole. But if you saile from A. right North so farre as the altitude of the Pole is augmented one de∣grée, then your ship shal be in C. and if you sayle by the first rombe towardes the East so farre as the Pole doth altar in altitude one degrée, then your shippe shall be in E. and thereby your way must néedes, be longer, and so consequently the more rombes you de∣cline from North to East, the longer is your way, and the more leagues must be accounted to one degrée of altitude, as the lines drawne from A. to E. F. G. H. I. K. and D. do shew. And what same euer is saide here of the quarter from North to East, the same is to be vnderstoode in all the other thrée quarters, that is, from North to West, from South to East, and from South to West. But if you will knowe how many leagues doe belong to

euery degrée according to the rombe whereby you sayle, then con∣sider well this Table here following.

The first Table.

Rombes.		Leagues.
1		17 ⅚
2		18 14/15
3		21 ½0
4		24 ¾
5		31 ½
6		45 ¾
7		89 ⅔

For in sayling from North or South towardes East or West so farre as you come to change one degrée of altitude of the Pole, the saide degrée doth require for the first rombe, &c.

Now then to know how much way you haue made in sayling, you must first know aswell the Latitude of the place from which you departed as of that place whereunto you be arriued: then by the foresaid Table séeke to knowe how many leagues doe belong to a degrée of that rombe whereby you haue sayled, for in multi∣plying the number of the leagues by the degrées of the difference of the two Latitudes, the product thereof will shew you how ma∣ny leagues you haue sayled, notwithstanding sith the way may be made longer or shorter by changing or shifting of the winde, it is néedefull that the Pylot haue consideration thereof, who by skil∣full coniecture must sometime eyther adde to, or take fro accor∣ding as néede shall require. Moreouer by the foresaid figure mar∣ked with letters, you may also easily vnderstande how much you change in Longitude, that is to say, how much you are distant from the Meridian of that place from whence you departed, be it eyther towardes the East or West, for he that sayleth from the point A. as is aforesaid right North or South, he remaineth al∣wayes vnder one selfe Meridian: but he that sayleth by the first rombe towards the East or West so farre as he changeth one de∣grée of Altitude, and arriueth to the point E. is now distant from his first Meridian so much as is the space betwixt C. and E. which we finde by computation to be thrée leagues and a halfe for one degrée of Latitude, which amounteth to twelue minutes of a de∣grée, and so of the rest of the rombes, as appeareth by this Ta∣ble here following.

The second Table.

Rombes	leagues	Degrees and minutes or Longitude.
first	3 ½	0	12
second	7 ¼	0	25
third	11 ⅔	0	40
fourth	17 ½	1	0
fift	26 ⅕	1	30
sixt	42 ¼	2	25
seuenth	880	5	2

For in sayling from North or Southe towardes East or West so farre as you change one degrée of altitude of the Pole you change also your Me∣ridian, and thereby your Lon∣gitude, the quantitie whereof answerable to euery rombe, is set downe on the right side of this Table.

And to make this more plaine by example suppose that you sayle from Lisbone, which is a famous port in Portingale, by the winde Southwest and by west, which is the fift rombe from south to West, so farre as you finde the altitude of the Pole to be 18. degrées lesse then at Lisbone. Now if you would know how ma∣ny leagues you haue sayled, and also how much the Meridian of that place is more westward then the Meridian of Lisbone, then doe thus. Looke in the first Table, and you shall finde that to one degrée of the fift Rombe doe belong 31. leagues and a halfe, which leagues being multiplyed by 18. doe make in all 582. leagues and ¾. which you haue sayled. then looke in the second Table, and you shall finde for the fifth rombe one degrée and 30. minutes of Longitude, which being multiplyed by 18. and a halfe, do make 27. degrées and ¾. of a degrée, for by so much is Lisbone more Eastward, then the place where you are. And whereas the first Table is made according to the proportion of right lines such as are commonly drawne in Mariners Cardes, Cogniet maketh another Table according to the proportion of circular lines, which for that it differeth very little or nothing from the first Table, I omit here to set it downe. But now because the first Table doth chiefely serue those that fayle either East or West in any Parallell betwixt the Equinoctiall and the 60. degrée of Latitude or Altitude of the Pole: And that from thence foorth by reason that they sayle by more oblique and spirall Circles doe make the longer voyage, Cogniet thought good to adde a thirde Table shewing how many leagues be answerable to one degrée of altitude to those that sayle eyther East or West in any Pa∣rallell

that is betwixt the Pole and the 60. degrée of altitude, which Table differeth not much from the others in the foure first rombs, but in the thrée last, that is in the 5. 6. and seuenth rombe it diffe∣reth greatly, and most in the seuenth as you may easily perceiue by comparing this and the first Table together.

The third Table.

	Deg	M		Leagues.
The first rombe hath	1	1	Which according to the proportion of 17. leagues & a halfe, for one de∣gree do make for euerye rombe so many leagues as this Table shew∣eth.	17	19/24
the second rombe	1	5	18	23/24
the third rombe	1	12	21	0
the fourth rombe	1	26	25	1/12
the fift rombe	1	50	32	3/12
the sixt rombe	2	42	47	¾
the seuenth rombe	5	44	100	3/3