TRACT 37.

OF GUNNERY.

299

iabove found by computation from the experimented veloci-ties. This fluid, on account of its great elasticity, movesmuch quicker through the above-mentioned openings, thanthe hall ever can move. Hence the diminution of the im-pelling force must he considerable, and must necessarilymake the velocity of the ball much less than what it wouldotherwise he. In order to assign the quantity-of the decreasefrom this cause, it is necessary to know with what velocitythe compressed elastic air, in the gun, passes through thevent, and by the sides of the ball. This degree of velocitycan never he communicated to the ball, since the powderacts on the hall only bv its relative velocity, that is, by somuch as the velocity of the ball is less than that of the flamewould be, if there was no ball at all, or if it was suddenlyannihilated. Since the ball, by its own mass, resists the mo-tion of the flame, as well as meets with resistance from ex-terna! causes, it is easy to conceive that the ball can neveracquire so great a velocity as the flame would acquire, if noobstruction lay in its way-. Hence it is obvious, that thegreatest velocity which the powder can communicate to theball, will always be less than that which the pure flame wouldacquire, in proportion to the weight of the ball it impels,and the resistance the ball meets with. And hence, it is ofthe greatest importance to obtain a knowledge of that velo-city. That it is immensely great, is evident from the cir-cumstance of its communicating such high velocities to theheaviest balls and shells, being probably not less than 3 or 4times that of the balls in the more ordinary cases. Theremay be several ways of determining this, either by theory orby experiments. But, preparatory to that determination,we shall first enquire what aid towards it may be further de-rived from our own experiments, especially' by another cor-rection of pur theorem for the ball’s velocity', on account ofthe waste of the elastic fluid by the vent and windage.

174. This subject has before been adverted to in arts. 77and 113 of the 34th Tract. It there appears that, upon anaverage, about the f part of the force is lost by the difference