the Force of fired Gunpowder. 249 
dirty grey, which changed to black upon being exposed to the 
air, had a pungent, acrid, alkaline taste, and smelt like liver of 
sulphur. It attracted moisture from the air with great avidity. 
Being moistened with water, and spirit of nitre being poured 
upon it, a strong effervescence ensued, attended by a very of- 
fensive and penetrating smell. Nearly the whole quantity of 
matter of which the powder was composed, seemed to have 
been transformed into this substance; for the quantity of elastic 
fluid which escaped upon removing the weight, was very incon- 
siderable ; but this substance was no longer gunpowder ; it 
was not even inflammable. What change had it undergone ? 
what could it have lost ? It is very certain the barrel was 
considerably heated in these experiments. Was this occa- 
sioned by the caloric , disengaged from the powder in its com- 
bustion, making its escape through the iron ? And is this a 
proof of the existence of caloric , considered as a fluid sui ge- 
neris; and that it actually enters into the composition of inflam- 
mable bodies, or of pure air, and is necessary to their combus- 
tion ? I dare not take upon me to decide upon such important 
questions. I once thought that the heat acquired by a piece of 
ordnance in being fired, arose from the vibration or friction of 
its parts, occasioned by the violent blow it received in the ex- 
plosion of the powder ; but I acknowledge fairly, that it does 
not seem to be possible to account in a satisfactory manner 
for the very considerable degree of heat which the barrel ac- 
quired in these experiments, merely on that supposition. 
That this hard substance, found in the barrel after an expe- 
riment in which the generated elastic vapour had been com- 
pletely confined, was actually in a fluid or elastic state in the 
moment of^ the explosion, is evident from hence, that in all 
