The mariners magazine, or, Sturmy's mathematical and practical arts containing the description and use of the scale of scales, it being a mathematical ruler, that resolves most mathematical conclusions, and likewise the making and use of the crostaff, quadrant, and the quadrat, nocturnals, and other most useful instruments for all artists and navigators : the art of navigation, resolved geometrically, instrumentally, and by calculation, and by that late excellent invention of logarithms, in the three principal kinds of sailing : with new tables of the longitude and latitude of the most eminent places ... : together with a discourse of the practick part of navigation ..., a new way of surveying land ..., the art of gauging all sorts of vessels ..., the art of dialling by a gnomical scale ... : whereunto is annexed, an abridgment of the penalties and forfeitures, by acts of parliaments appointed, relating to the customs and navigation : also a compendium of fortification, both geometrically and instrumentally / by Capt. Samuel Sturmy.

How to make the Scale of Leagues.

THE Quadrant being drawn, as before-directed, take 110 Leagues and lay from A to B, and draw the Line MNB at Right Angles thereunto: and if it be for a particular Chart, as that before-going, draw Lines from the Center through every particular Latitude; as you see in the Quadrant I have done, to make a Scale for the blank Chart before-going, from the Latitude of 49 deg. 30 min. to 55 deg. 30 min. So that if you would know the length of 110 Leagues in the Latitude of 50 Degrees, lay a Ruler upon 50 deg. in the Arch of the Quadrant and the Center, and draw the Line A ♌, and that is the length of 110 Leagues in that Latitude. So that if you draw Parallel-lines to MN, through every 10 Leagues in the Side AB, you will have the length of every 10 Leagues in every Latitude, as you may plainly see in the Quadrant: and so you may do for every League, as you see the little Checkers be∣twixt the Latitude of 20 deg. and 30 deg. for 10 Leagues between Latitude of 50 deg. and 56.

Suppose you would know the length of 40 Leagues in the Latitude of 50 deg. Extend the Compasses from A to K, and that Distance is 40 Leagues in that Latitude: And in like manner work by the rest in any other Latitude.

If you would make this into a Scale, as the Figure YM in N; First in the Qua∣drant extend your Compasses from the Center A, to the Intersections of the Lines drawn through every Degree MNB, and lay them down upon the Side of the extreme Latitude of your Chart, as A, O, P, Q, Y, M, with the small Arches, as you see I have done from M to NY, and that is the length of the Meridian-line of

your Scale or Degree of Latitude MY; therefore draw the Parallel-lines YN and M m for the extreme Parallels of your Scale: Then extend your Compasses from Y in the Quadrant, to each of the Intersections of these small Arches that are drawn from the Intersections on the Tangent-line MN; and from 25 deg. uppermost, lay that Extent downward for the Parallel of 55 deg. of Latitude, as the Line above the lowermost; and so lay down all your Latitudes by these small Arches, in like man∣ner; and so neatly divide the Side of your Scale MY of Deg. of Latitude: Then draw Parallel-lines to all these Degrees, as you see: Then extend the Compasses from the Center of the Quadrant to M, for the length of the lowermost Line of your Scale M m for 110 Leagues. Then extend the Compasses from the Center of the Quadrant to N, which is the length of 110 Leagues in the Latitude of 25 deg. and it is the Di∣stance of the uppermost Line YN of your Scale; and draw N m the outside of your Scale 120 Leagues: So take every 10 Leagues from the Center A, in the Line AM, in Latitude 56 Degrees, and divide the lowermost Line of the Scale; and the like do in the Latitude of 25, for to divide the uppermost Line of the Scale; and draw Lines through each of them, which will divide all the rest of the Parallel-lines in each Latitude into 10 Leagues apiece, and number them as you see I have done; and divide the first 10 Leagues by the Meridian-line of the Scale, into 10 Equal parts below and above, and draw Lines through each of the Divisions: So have you neatly divided your Scale, and every Degree of Latitude thereof, into Leagues, to 100 and 10 odd Leagues; which will measure any Distance in a Chart, made according to the Degrees of Latitude and Longitude in the foregoing Chart.

For to know the Rhomb between any two Places, shall be shewed in the Use of the general Sea-Chart following, by a Protracting Quadrant, and also how to find the Place of any Ship in Mercator's Chart, and to lay down any Traverses.