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.

The Ʋse of these Tables.

LEt it be required to draw the Proportional Dimension of a Regular Fort of 6 Sides: As for Example, in the fourth Figure, whose Side AB must be divi∣ded into 100 equal parts, and each part supposed to be subdivided into 10 parts; so have you 1000 parts, which shall suffice. Now proceeding according to former Di∣rections, until you come to make choice of your Capital Line, you shall here find in the second Table, which is best for the purpose, under the Figure 6, and right against the word Capital in the first Column, 2602, but 260 will serve: Take the

same from the Scale of Equal parts, and lay it from the Bastion Point at A, and it falls in the Point E, which will be the Center of the Bastion. From thence you may lay down the Gorge Line out of the Table, which is 148 unto M: So will the Front AL be 296, and the Flank ML. The Curtain, being once and a half the length of the Front, will be MN 444. Thus you may do for any of the rest. These Ta∣bles are useful for Irregular Forts; But first I will shew you the Height, Breadth, and Scarpings of the Rampire, Parapet, Ditch, &c. of these Sconces, as they are represented in the Profile, or Section, as followeth.

[illustration] geometrical diagram

The Breadth of the Rampire may be 24, 30, or 40 Foot; but here AB is but	32
The Inward Scarp AC	6
The Height of the Rampire CD	6
The Breadth of the Walk of the Rampire DE	10
The Breadth of the Bank or Foot-pace of the Parapet EF	3
and the Height of the same Foot-pace	1 ½
The Inward Scarp of the Parapet FG	1
The Inward Height of the Parapet GH	6
The Breadth of the Parapet at the Foot FI	10
The outward Scarp of the Rampire BK	3
The Inward Scarp of the Parapet IL	2
The Outward Height of the Parapet LM	4
The Thickness of the Parapet at the top MN	7
The Brim of the Ditch BO	3
The Breadth of the Ditch at the top OP	32
The Scarp of the Ditch OQ	6
The Depth of the Ditch QR	6
The Breadth of the Ditch at the Bottom RS	20