or REBOUND, the starting backward of a fire-arm after an explosion. Mersenius tells us, that a cannon 12 feet in length, weighing 6400lb. gives a ball of 24lb. an uniform velocity of 640 feet per second. Putting, therefore, $W = 6400$, $w = 14$, $V = 640$, and $v =$ the velocity with which the cannon recoils; we shall have (because the momentums of the cannon and ball are equal) $W \cdot v = w \cdot V$; and so $v = \frac{w}{W} \cdot V = \frac{24 \times 64}{6400} = 2.4$; that is, it would recoil at the rate of 2.4 feet per second, if free to move.