1. That gunpowder fires almost instantaneously. 2.
That the velocities communicated to balls or shot of the same weight by different quantities of powder are nearly in the subduplicate ratio of those quantities : a small variation in defect taking place when the quantities of powder become great. 3. And when shot of different weights are employ ployed, with the same quantity of powder, the velocities communicated to them are nearly in the reciprocal subdu plicate ratio of their weights. 4. So that, universally, shot which are of different weights, and impelled by the firing of different quantities of powder, acquire velocities which are directly as the square roots of the quantities of powder, and inversely as the square roots of the weights of the shot, nearly. 5. It would therefore be a great improve ment in artillery to make use of shot of a long form, or of heavier matter ; for thus the momentum of a shot, when fired with the same weight of powder, would be increased in the ratio of the square root of the weight of the shot. 6. It would also be an improvement to diminish the wind age ; for by so doing, one third or more of the quantity of powder might be saved. 7. 1Vhen the improvements mentioned in the last two articles are considered as both taking place, it is evident that about half the quantity of powder might be saved, which is a very considerable ob ject. But important as this saving may be, it seems to be still exceeded by that of the article of the guns ; for thus a small gun may be made to have the effect and execution of another of two or three times its size in the present mode, by discharging a shot of two or three times the weight of its natural ball or round shot: And thus a small ship might discharge shot as heavy as those of the great est now made use of.
In the year 1781 Count Rumford instituted a series of experiments with musket barrels. The machinery which he used was ingeniously connived and well executed, and his object was to determine the initial velocity of bullets, the recoil of the barrel, the effect of firing the charge in different parts of it, and the most advantageous situation for the vent. The following were the principal results which he obtained. He found that when the weights and
dimensions of the bullets are the same, their velocities, when discharged from the same piece, are in the subdupli cate ratio of the weight of the charges; and he concludes, from numerous experiments, that the vent may be placed in any part of the chamber where it will best answer on other accounts. Hence Count Rumford recommends that the bottom of the bore should be of a hemispherical form ; that the vent should be brought directly through the side of the barrel in a line perpendicular to its axis, and point ing to the centre of the hemispherical concavity of the chamber.
In these experiments, the ballistic pendulum of Robins was employed ; but in consequence of a suggestion con tained in Robins's new principles of gunnery, Count Rum ford proposed, and put in practice, another method of deter mining the velocities of bullets, by suspending the gun in a horizontal position by two pendulous rods, and determin ing the . velocity of its recoil from the arc of its ascent, measured by a ribbon, as in the ballistic pendulum.
V—U The velocity of the bullet will be v= B X NV; where W is the weight of the gun, V the velocity of its recoil when fired without a bullet, V the velocity of the recoil when the same charge impels a bullet, B the weight of the bullet, and v its velocity. By comparing the results ob tained in this way, with others obtained from the ballistic pendulum, Count Rumford found, that in several cases they agreed, but that in others the differences were so great, that the new method ought not in general to be relied upon.
Another very extensive set of experiments was under taken in the year 1783, under the direction of Major Bloomfield, and by the orders of of Richmond, Master-general of the Ordnance. They were carried on in the summers of 1783, 1781, 1785, 1787, 1788, 1789, 1791, &c. principally with a view to the following objects : 1. To determine the velocity of balls impelled by equal charges, from pieces of different lengths, but of the same weight and calibre, 2. To determine their velocities with different charges, when the weight and length of the gun are the same.