Page:Philosophical Transactions - Volume 002.djvu/75

(474)

Line with the under-side of the Cylinder of the Peece. Then, between the Gun and the Mark at several places, place pieces of Canvas, Sheets of Paper pasted together, or the like, upon Stakes fixt in the ground, so as the underside, being level with the Horizon, may just touch the Visual line, that passeth from the Eye to the upper-side of the Mark; when the Eye is placed in the Line, that passeth from it to the upper-side of the Cylinder of the Gun; the Canvas being so broad and long, that, if the Bullet pass through it two or three foot higher than the Level of the Mark, or of either hand, the hole it makes, may make it known, how much it flieth higher than the Level of that place. Such piece of Canvas, &c. may be placed; one, at half the distance between the Gun and the Mark; another, halfway between the first, and the Mark, &c. And if it be found, that even at so small a distance the Bullet falls lower than the Mark, if it touch not the Canvas, the Gun may be next time raised a little, and so on, till the Bullet hit the Mark, or as high as it: And if at first it fall as high as the Mark and cut the Canvas, the Mark and Canvas may be brought neerer the Gun, till it needs be done no more: Afterwards the Mark may be removed to greater and greater distances, till, to hit the Mark, it fly higher, than some or all the interposed Canvasses: And thus the Experiment. is to be repeated and varied at pleasure.

II.To know, what Quantity of Powder, is the just Charge of any Peece, so as it maketh the farthest Shot, and fires totally.

1. Raise the Gun to a mean Random, as of 20 or 25 degrees, and Shoot with the ordinary Charge of Powder, in some convenient ground, where the fall of the Bullet may be easily seen, and having made a Shot, measure the distance with a Chain, between the hole made by the Bullet, and the Muzzle of the Gun.

2. Then, instead of a full Charge of Powder uses in the first Shot, take ${\tfrac {1}{16}}$. part lesse, or some such proportion, for the next tryal; doing all things else as before.

3. For a third, fourth, or more tryals, diminish still the Quantity of Powder by ${\tfrac {1}{16}}$. at a time, till the Shot be considerably Shorter, than at first.

4. Then take ${\tfrac {1}{16}}$. more than the first Charge, and do all things else as before, and so continue more tryals, increasing still the Quantity of Powder in the same proportion, every new tryal, till you find the increase of the Charge does not make the Peece

Shoot