Experiments upon Gtmpowder. 51 



Let us see how this method of determining the ve- 

 locities of bullets will answer in practice. 



In the 94th experiment, the recoil, with 165 grains of 

 powder without a bullet, was c^.^ inches, and in the 95th 

 experiment, with the same charge, the recoil was c^.6 

 inches. The mean is c^.^^ inches, and the length of the 

 rods by which the barrel was suspended being 64 inches, 

 the velocity of the recoil (= U), answering to 5.55 

 inches measured upon the ribbon, is that of 1.1358 feet 

 in a second. 



In five experiments with the same charge of powder, 

 and a bullet weighing 580 grains, the recoil was as fol- 

 lows, viz. : — 



The 20th experiment 14.73 inches. 



5)73. (= 14.6 inches at a mean. 



And the velocity of the recoil (:=: V) answering to 

 this length (14.6 inches) is thit of 2.9880 feet in a 

 second; consequently V — U, or 2.9880 — 1.1358 is 

 equal to 1.8522 feet in a second. 



But as the velocities of the recoil are known to be as 

 the chords of the arcs through which the barrel ascends, 

 it is not necessary, in order to determine the velocity of 

 the bullet, to compute the velocities V and U ; but the 

 quantity V — U, or the difference of the velocities of 

 the recoil when the given charge is fired with and with- 

 out a bullet, may be computed from the value of the 

 difference of the chords by one operation. Thus the 

 velocity answering to the chord 9.05=14.6 — ^.^c^ is 

 that of 1.8522 feet in a second, which is just equal to 

 V — U, as was before found. 



