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42.

full lines in Fig. 12, and then calculating the mass of this reduced chamber, from the measured density of the steel. The minimum masses of chamber per gram of powder plus wadding, estimated in this way, were 143, 130, and 120 grams, respectively, for experiments 50, 51, and 52. In the last two cases, a smaller breach block could doubtless have been used, as evident from Fig. 12; and in the first two cases, the chamber wall, itself, could safely have been reduced in thickness. More important still,a "built-up" construction would much reduce the mass as has already been explained. 

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 accidently reflected in the nozzle of the gun, ^[[show]] the nozzle appearing stationary in the photograph, thus demonstrat^[[ing]] 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.