2 77 
the Force ofjired Gunpowder. 
It appears from the foregoing table, that in the afternoon of 
the ist of July, the weight (which was a heavy brass cannon, 
a 24 pounder, weighing 8081 lbs. avoirdupois), was not raised 
by 12 grains of powder, but that 13 grains raised it with an 
audible though weak report. That the next morning, July 
2d, at 10 o’clock, it was raised twice by charges of 12 grains. 
That in the morning of the 3d of July, it was not raised by 
12 grains, nor by 13 grains ; but that 14 grains just raised it. 
That in the afternoon of the same day, two experiments were 
made with 14 grains of powder, in neither of which the weight 
was raised ; but that in another experiment, in which 15 grains 
of powder were used, it was raised with a moderate report. 
That in the morning of the 8th July, in two experiments, one 
with 15 grains, and the other with 13 grains of powder, the 
weight was raised with a loud report ; and in an experiment 
with 12 grains, it was raised with a. feeble report. And lastly, 
that in three successive experiments, made in the morning 
of the 17th of July, the weight was raised by charges of 12 
grains. 
Hence it appears, that under circumstances the most favour- 
able to the developement of the force of gunpowder, a charge 
(=12 grains) filling of the cavity in which it is con- 
fined, on being fired, exerts a force against the sides of the 
containing vessel equal to the pressure of 9431 atmospheres ; 
which pressure amounts to 141465^3. avoirdupois on each 
superficial inch. 
Mr. Robins makes the initial, or greatest force of the fluid 
generated in the combustion of gunpowder, (namely when the 
charge completely fills the space in which it is confined), to 
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