involved in the Construction of Artillery. 269 



diminish still further the moment of time before required for the change, from 

 the solid to the gaseous state. The distress upon the gun, however, is depen- 

 dent upon the shortness of this time of explosion. 



243. Neglecting the inertia of the charge itself, and supposing it fired from 

 the centre, so that its evolved gases shall have equal density against the breech 

 and the shot, if P and P' be the weights of the shot and of the gun, the total 

 vis viva of the explosion is, 



p p 



9 9 



and 



P P 



t-V' = -V'\ (58) 



9 9 



the vis viva of the shot, and of the recoil. 



244. Assuming that the " work done" upon the shot, and upon the gun, is, in 

 the case of every explosive agent, proportional to the volume of gases evolved, 

 and that this is proportional to the weight of the charge, 2>, we have, for different 

 velocities, and weights, of shot and charge, the proportions 



PV'-.P'V'-.-.p-.jf. 



For, the same shot P=P, with different charges, 



V'-.V-.-.p-.p', (59) 



and for the same charge p) —p\ with different shot, 



PV' = FV'\ 

 or, 



V:V'::y{P'):y(P). (60) 



This law, first given by Hutton, as deduced from his experiments, has been 

 subjected to fresh investigations by Colonel Mallet, of the French Artillery, by 

 General Piobert, and others, and has been verified for gun-cotton as well as for 

 gunpowder. 



245. In the following Table the results of some of these experiments are 

 given, in which the vast differences in effect, due to difference of aggregation, 

 composition, &c., in the charge, ai'e manifested : — 



VOL. XXIII. 2 N 



