232 Count Rumford’s Experiments to determine 
reason to conclude was the real cause of these variations, and 
of all the principal difficulties which attended the ascertaining 
the force of fired gunpowder by the methods I had hitherto 
pursued. 
It has generally been believed, after Mr. Robins, that the 
force of fired gunpowder consists in the action of a per- 
manently elastic fluid, similar in many respects to common 
atmospheric air; which being generated from the powder in 
combustion, in great abundance, and being moreover in a 
very compressed state, and its elasticity being much aug- 
mented by the heat (which is likewise generated in the com- 
bustion), it escapes with great violence, by every avenue ; and 
produces that loud report, and all those terrible effects, which 
attend the explosion of gunpowder. 
But though this theory is very plausible, and seems upon a 
cursory view of the subject to account in a satisfactory man- 
ner for all the phaenomena, yet a more careful examination will 
shew it to be defective. There is no doubt but the permanently 
elastic fluids, generated in the combustion of gunpowder, assist 
in producing those effects which result from its explosion; but 
it will be found, I believe, upon ascertaining the real expansive 
force of fired gunpowder, that this cause, alone, is quite inade- 
quate to the effects actually produced ; and that, therefore, the 
agency of some other power must necessarily be called in to 
its assistance. 
Mr. Robins has shewn, that if all the permanently elastic 
fluid generated in the combustion of gunpowder be compres- 
sed in the space originally occupied by the powder, and if this 
fluid so compressed be supposed to be heated to the intense 
heat of red-hot iron, its elastic force in that case will be 1000 
