[37] It has been known long since, that this concussion, or what may be called a general contusion, is one of the principal causes of the danger arising from gunshot wounds, and more or less from those of all kinds of fire arms; but at present I do not recollect to have seen the mechanism of this effect so well explained as in this performance. The rapidity with which the air strikes, compensates what it wants in density: Those who love to reduce every thing to calculation, will be able exactly to determine this effect by the rule of proportion: Supposing on one hand, a stream of air, which has acquired, by the motion of the ball, a given velocity, and which acts upon a man with this degree of velocity; supposing on the other hand, a man falling upon a floor, likewise with a given degree of velocity, the effect will be equal, if the velocity of air, is to the man who falls, as the density of the board is to that of the air; or, more briefly, if the contusing bodies be in an inverse ratio of their densities. I am even induced to believe, that when the velocity is augmented to a certain degree, its effect is augmented in a greater proportion than its increase; or, to speak algebraically, that its effects ought to be expressed by some quality of its degrees; thus the effect of a velocity of 150 degrees, would be to the effect of a velocity of 125, not as 150 : 125 or as 6 : 5 but as the square, or perhaps some other quality of 150, to the square or the correspondent quality of 125.