Another way to Dispert any Piece.

If you have a pair of Callipers, as in the general Figure ACB, as you take the diameter of a Shot, and apply it to a Scale Divided into 8 or 10 parts, to know the Contents thereof; so with the Callipers take the greatest thickness or diam. of the Base Ring, and by your Scale see how much that is; as admit that the length of the Line a:b:c:d, where the diam. of the Base Ring, then take the diam. of the Muzzle Ring; as admit it be a, b, as you may try by the Figure of the Gun in the general Figure; then Divide the difference b d into 2 equal parts, and one of them is the Dispert, put it upon the Muzzle of the Gun as CB, and stick it fast on the top of the Muzzle Ring with a little Pitch or Wax, and from the Base Ring at A in the Fi∣gure to the top of the Dispert at B, take aim to the Mark you would shoot to, and that is the way to hit; but it Callipers be wanting, take a Stick that is straight and flat, and 2 Strings with two Musket Bullets at the end, and two Loops made at the other end, the Stick being something more than the diam. at the Base Ring, and put the Stick upon the top of the Ring at the Muzzle, as you see the Fig. HK on the Gun, and put the Strings so nearer and farther, until they only touch the side of the matter of the Muzzle Ring, and mark the Loops on the Stick, and put the Stick on the Base Ring, and do in like manner, and mark the Sticks; and the Work will be the same, as it were taken by the Callipers; and the difference of the two Notches on the Stick will be ab the Base Ring, and ab the Notches of the diam. of the Muzzle Ring, and half the dif∣ference bc or cd is the Dispert, as before, if the Piece be true bored.