From this I infer that, in the first trial, the velocity of the ball was not so great, but that the air escaped past it, by what is technically called the windage, allowing it to strike the plug at the end of the barrel with sufficient force to alter the shape of the lead in the manner described. The second trial gave an increased velocity; the opposing forces being so nearly balanced that the ball scarcely reached the end of the barrel, and was very little injured. In the third trial the velocity became so great, and the air was condensed to such an extent, that the ball struck upon a cushion-like surface so highly elastic that it was extracted without the least injury to its shape. The last charge was too powerful, inasmuch as the lateral pressure of compressed air rent the tube asunder. The one great cause of this and other barrels bursting, arises from the velocity becoming too great, and thus driving back the air upon itself, until the mutual repulsion of the particles forms an almost impenetrable barrier, exerting a lateral pressure on the barrel, and resisting the passage of the elastic fluid. To make the explanation plain; supposing that the charge had condensed the air for the distance of three or four inches immediately preceding it, and then come to rest, the waves of vibration, travelling at the rate of 1,300 feet per second, would communicate to the remainder of the column the same pressure, and an equilibrium would take place. But this not being the case, and the air becoming still more highly compressed by the velocity not decreasing but increasing, the lateral pressure becomes greater than the fibres of the iron are able to withstand, and consequently the barrel is burst. Many accidents arise from this cause solely, and without any blame being attached to either the maker or user of the gun. While on this subject, we may remark that this is the more likely, inasmuch as the powder with which barrels are proved is not the strongest, and is also of a large grain; so that it is quite within the range of probability that a barrel may, and it does often, stand proof, and yet burst when it comes to be used with extremely fine-grained strong powder; as it is quite clear that a high velocity must create danger.