In the first attempt I found the results to vary with the weight of the pendulum of iron plate, and that it was necessary to obtain uniformity of size and surface; as it must be comprehended that the only resisting medium to the pendulous plate was atmospheric resistance, and a dissimilarity of size of surface would invariably give different results. Having a number of plates of the different thicknesses hereafter described, I continued increasing the charge from a definite quantity, until the projectile was driven with sufficient velocity to perforate the plate suspended. The gun selected for this purpose was of heavy material, weighing nearly seventeen pounds, it was three feet long, the metal of the barrel as thick at the muzzle as at the breech, and carried a spherical ball of sixteen to the pound, or one ounce, and which fitted tight with the thinnest patch procurable. The bore was perfectly cylindrical, and plain inside, being polished longitudinally to a high state of fineness. With a charge of twelve drachms of Curtis and Harvey’s diamond grain powder, the ball went through the half-inch plate, but went only a few yards further; denoting that the effort necessary had nearly exhausted its velocity and momentum. The recoil of the gun was of the most severe description, and the shoulder had to be protected for many explosions previous to this high charge. The larger sized grain was insufficient, ten drachms effecting the greatest extent of power it seemed capable of, and it became quite apparent that the tube would not explode more powder, as indications convinced me: when any more was added, a portion came out unburnt. The force necessary to effect this, by the above calculation, is 46,795 pounds. The next plate was 7-16ths thick, and a charge of ten drachms punched the piece out clean; nine and a half drachms were equal to it, when the centre of the pendulum could be hit fairly, because there was then an equal resistance from the atmosphere, which cannot exist in cases where the edge of the disc receives the blow. I got with ease a perforation in a 6-16ths plate, with a charge of either fine or coarse powder, not exceeding eight drachms; a charge of seven drachms of fine grain was unequal to the task; but seven drachms of the coarse showed evidently greater effects produced, though the perforation was not perfect. Six and a half drachms of No. 2 grain penetrated a plate of 5-16ths thick easily, while it took full six and three-quarters drachms of fine grain; five drachms of the larger perforated a quarter-inch plate, but it took full five and a half drachms of fine grain to effect the same; while a 3-16ths plate took three and three-quarters drachms of fine, or three and a quarter of No. 2 grain; and 1-8th plate was easily punched by a charge of two and a half drachms coarse or three drachms fine. I will place the relative results in a table, with the force effected by each:--