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.

SECT. IV. How to cast up the Content of any piece of Land in Acres, Roods and Perches by Mr. Gunter's Chain.

BY a Statute made the 33 of EDVVARD the I. an Acre of Ground ought to contain 160 square Perches, and every Rood of Land 40 square Perches, and every Perch contains 16 ½ Foot; and 4 Perches, Poles, or Luggs in breadth, and 40 in length makes an Acre: which multiplyed together is 160, Half an Acre is 80, a Quarter 40 square Perches.

[illustration] geometrical diagram

Suppose the Figure ABCD were a square piece of Ground as the Marsh of Bristol, and were 15 Chain 16 Links every way: Then to find how many Acres, Roods and Perches are in it, do thus. Square the sides, that is, Multiply one in the other, and cut off the 5 last Figures to the right Hand, and that before is Acres: what re∣mains Multiply by 4 (for 4 Roods makes an Acre) and cut off 5 Figures as before, and the comma: is Roods; and that which

remains, multiply by 40 the number of Perch in a Rood, and cut off 5 Figures to the right hand of the Product; and in like manner you have the odd Perches. This Ex∣ample will make all clear and plain.

So you will find 15 Chains, 16 Links Multiplyed together, as before directed, will produce 22, 98256: the 5 last Figures cut off to the left hand, remains before the Comma 22, which is 22 Acres, and the 5 Figures multiplyed by 4, the Product is 393024:

15:16

15:16

90 96

1516

7580

1516

5 Fi∣gures cut off on the left hand, the Comma is 3 Roods, and the 5 last Figures multiply∣ed by 40, cut off 5 Figures, and the rest will be 37 Perch.

Acres 22⌊98256

4

Roods 3⌊93024

40

Perch 37 ⌊20960

By the Line of Numbers.

Extend the Compasses on the line of Numbers on the Scale of Scales from □ which is at 160 unto the side of the Square AB 15 Ch: 16 ••in. which is 60 Perch and above ½, the same distance will reach from the same 60 ½ Perch, to 22 Acres, 3 Roods, and 37 Perch, and the 20960 part of a Perch.