The above Angle FAE, may be had without a Secant as before, thus, Its Complement 29°. 47', will give FAE, as before. The Questions that may be proposed on this Head, being innumerable, we have chofen to give only a few of the most useful. OF Containing a particular Defcription of the feveral Inftruments used in Surveying, with their respective Ufes. And firft, T Of the CHAIN. HE Stationary Distance, or Mearings of Ground are measured either by Mr. Gunter's Chain of four Poles or Perches, which confifts of 100 Links; (and this is the most natural Division) or by one of 50 Links, which contains two Poles or Perches: But because the Length of a Perch differs in many Places, therefore the Lengths of Chains and their respective Links will differ also. The English Statute-Perch is 5 Yards, the TwoPole-Chain is 11 Yards, and the Four-Pole one is 22 Yards: Hence the Length of a Link in a StatuteChain is 7.92 Inches. There are other Perches used in different Parts of England, as the Perch of Wood-land Measure, which is 6 Yards; that of Church-land Measure, which is 7 Yards (or the fame with the Plantation Perch) and the Foreft Measure Perch, which is 8 Yards. S The The Irish, or Plantation Ferch is 7 Yards, as before; the Two-Pole Chain is 14; and the Four-Pole one is 28 Yards: Hence the Length of a Plantation Chain is 10.08 Inches. The Scotch Perch is 18 Feet, or 61⁄2 Yards, or 6 Scots Ells. In the Shire of Cunningham in Scotland, their Perch is 182 Feet, and this Perch is used in fome few Places in the North Part of this Kingdom, as the Statute Perch is in fome other Parts. For the more ready reckoning the Links of a Four-Pole Chain, there is a large Ring, or fometimes a round Piece of Brafs fixed at every 10 Links; and at 50 Links, or in the Middle, there are 2 large Rings. In fuch Chains as have a Brafs Piece at every 10 Links, there is the Figure 1 on the firft Piece, 2 on the fecond, 3 on the third, &c. to 9. By leading therefore that End of the Chain forward, which has the leaft Number next it, he who carries the hinder End may easily determine any Number of Links: Thus if he has the Brafs Piece Number 8, next to him, and 6 Links more in a Distance, that Diftance is 86 Links. After the fame Manner 10 may be counted for every large Ring of a Chain which has not Brafs Pieces on it, and the Number of Links is thus readily determined. The Two-Pole Chain has a large Ring at every 10 Links, and in its Middle, or at 25 Links, there are 2 large Rings; fo that any Number of Links may be the more readily counted off, as before. The Surveyor.fhould be careful to have his Chain measured before he proceeds on Business, for the Rings |