If a cartridge be placed in the centre of an open barrel eight feet in length, having a bullet abutting at each end large enough to fill the barrel, and a touch-hole is drilled as near the centre of the cartridge as possible, when it is fired, the balls will certainly be discharged from the barrel, but with a very small degree of force: in fact, merely driven out. With the same instrument, vary the experiment: place in it a cartridge charged with one ball, three feet from the muzzle, leaving a column of air five feet in length to act against the explosive force of the gunpowder, and the ball will be driven one hundred yards with considerable force. Again, let a third cartridge be introduced similar to the last, two feet from the muzzle, increasing the column of air to six feet; and the result, in distance and velocity, will nearly double what has been obtained by the last experiment; tending to prove that air thus forced back upon itself obtains a density, and consequent resisting influence, nearly equal to a well-screwed breech. In order to test this principle further, I put into the same tube a double charge of gunpowder, merely backed by a wadding, two feet from the muzzle, and then rammed down four balls as tight as possible into the short portion; in discharging it, the tube was burst immediately in rear of the charge.
In another experiment, I took a common musket barrel, having a plug of iron firmly fixed into the muzzle; the breech being unscrewed, and a ball introduced one-tenth of an inch less in diameter than the bore of the barrel, together with one drachm of gunpowder, I then fired the gunpowder, and the explosive matter escaped by the touch-hole. On examination, it was found that the ball was flattened to the extent of one-third of its sphere. The charge for the next experiment was increased to two drachms; when the ball in the discharge struck the muzzle very slightly, altering its shape in the least conceivable degree. The charge was next increased to three drachms, and the ball was extracted without any perceptible defect. In the fourth trial, another drachm was added, with which the effect was greater than the tube was able to resist; it was in consequence burst, about three inches from the muzzle.