190 Historical Review of Experiments 



the barrel was always hotter when the charge had con- 

 sisted of powder alone than when loaded with one or 

 more bullets. 



I had, up to this time, no suspicion but that the 

 piece, on being discharged, became warm as an immedi- 

 ate consequence of the heat caused by the burning of 

 the gunpowder ; now, however, I was convinced by 

 the result of the above-mentioned experiment, that this 

 supposition was entirely without foundation. 



For if we should hold that the gun in question was 

 actually heated by the inflammation of the powder, 

 since the flame would issue from the piece much more 

 rapidly when the charge consisted of powder alone than 

 when the same charge had to force out one or more 

 bullets, it would follow that a much higher degree of 

 temperature would be reached in the latter case than in 

 the former. But since the above-mentioned experiment 

 shows the contrary, it follows that the heating of the 

 piece in question is not due to the combustion of the 

 powder, but to the vibrations caused by the concussion 

 within the barrel, and to the operation, as rapid as it 

 is brief, of the elastic fluid generated by this com- 

 bustion. 



No one is ignorant of the fact that a heavy blow is 

 much more effective in producing heat in a solid body 

 than a lighter one ; and if the hypothesis be well 

 founded that heat is nothing more than a continu- 

 ous, more or less rapid, vibratory motion among the 

 particles of solid bodies, this phenomenon is easily 

 explained. 



Nothing is more certain than that the shock taking 

 place within the barrel, in the case of the above-men- 

 tioned experiment, by the combustion of the powder, 



