36 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. '/I 



It should be mentioned that, for any particular chamber, it will be 

 necessary to determine the maximum possible powder charge to a 

 nicety, from the fact that, as modern rifle practice has demonstrated, 

 one charge of dense smokeless powder may be perfectly safe for any 

 number of shots, whereas a slightly larger amount, or the same 

 amount slightly more compressed (a state in which the powder must 

 exist in the present chamber) will result in very dangerous pressures. 



But the whole question of ratio of mass-of-powder-to-chamber is 

 without doubt relatively unimportant for the following reason : The 

 photographs of the flash, in experiments 9 and 11, in which the flash 

 was accidentally reflected in the nozzle of the gun, shoV the nozzle 

 appearing stationary in the photograph, thus demonstrating that the 

 duration of the flash is very small ; but this, as already explained, 

 is much longer than the time during which the gases are leaving the 

 nozzle. The time of firing is, therefore, extremely short. This is 

 to be expected, inasmuch as the high pressure in the chamber sets in 

 motion only the small mass of gas and wadding, and hence must 

 exist for a much shorter time than the pressure in a rifle or pistol. 

 For this reason the heat such as is developed in the machine-gun, due 

 to the hot gases remaining in the barrel for an appreciable time dur- 

 ing each shot, as well as that due to the friction of the bullet, will be 

 absent in the type of rapid-fire mechanism under discussion. Hence 

 a large number of shots, equivalent to a mass of powder greatly 

 exceeding that of the chamber, may be fired in rapid succession, with- 

 out serious heating.''* 



