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.

PROBL. XXXII. How to make a Triangle which shall contain any Number of Acres, Roods, and Perches, and whose Base shall be equal to any (possible) Num∣ber given.

LEt it be required to make a Triangle which shall contain 6 Acres, 2 Roods, 25 Perches, whose Base shall contain 50 Perches. You must first reduce your 6 Acres 2 Roods, and 25 Perches, all into Perches, after this manner.

First, Because 4 Roods makes 1 Acre, multiply your 6 Acres by 4. makes 24; to which add the 2 odd Roods, so have you 26 Roods in 6 Acres 2 Roods; then because 40 Perches makes 1 Rood, multiply your 26 by 40, which makes 1040, to which add the 25 Perches, and you shall have 1065, and so many Perches are contained in 6 Acres, 2 Roods, and 25 Perches.—Now to make a Triangle that shall contain 1065 Perches, and whose Base shall be 50 Perches, do thus; double the number of Per∣ches given, namely 1065, and they make 2130; then be∣cause the Base of the Trian∣gle must contain 50 Perches, divide 2130 by 50, the Quo∣tient will be 42 ⅗ which will be the length of the Perpen∣dicular of the Triangle. This done, from any Scale of equal Parts, lay down the Line BC equal to 50 Perches; then upon C raise the Perpendicular CE, equal to 42 ⅗ Perches, and draw the Line AE, pa∣rallel to BC; then from any Point in the Line AE, as from G, draw the Line BG, and GC, including the Triangle BGC, which shall contain 6 Acres, 2 Roods, 25 Perches, which was required.

[illustration] geometrical diagram