263 
the Force of fired, Gunpowder. 
considerably facilitate the computations necessary in order to 
ascertain the ratio of the elasticity of this fluid to its density. 
The elastic force of the fluid generated in the combustion of 
the charge of powder, is measured by the weight by which it 
was confined, or rather by that which it was just able to 
move, but which it could not raise sufficiently to blow the 
leathern stopper quite out of the mouth of the bore of the 
barrel. 
This weight in all the experiments, except those which were 
made with very small charges of powder, was a piece of ord- 
nance, of greater or less dimensions, or greater or less weight, 
according to the force of the charge ; placed vertically upon its 
cascabel, upon the steel hemisphere which closed the end of 
the barrel ; and the same piece of ordnance, by having its bore 
filled with a greater or smaller number of bullets, as the occa- 
sion required, was made to serve for several experiments. 
The weight employed for confining the generated elastic 
fluid, is expressed in the following table i n pounds avoirdupois ; 
but in order that a clearer and more perfect idea may be 
formed of the real force of its elastic fluid, I have added a 
column in which its force, answering to each charge of pdw- 
der, is expressed in atmospheres. 
The numbers in this column were computed in the follow- 
ing manner. The diameter of the bore of the barrel at its 
muzzle being just ^ of an inch, the area of its transverse sec- 
tion is 0.049088 of a superficial inch ; and assuming the mean 
pressure of the atmosphere upon 1 superficial inch equal to 
i5lbs. avoirdupois, this will give 0.73631 of a pound avoir- 
dupois for that pressure upon 0.049088 of a superficial inch, 
or upon a surface equal to the area by which the generated 
