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the Force of fired Gunpowder. 
action of the powers which produce them are computed. For 
it is not in general very difficult to assume such principles 
as, when taken together, may in the most common known 
cases answer completely all the conditions required. But in 
such cases, if the truth be discovered with regard to any one 
of the assumed principles, and it be substituted in the place of 
the erroneous supposition, the fallacy of the whole hypothesis 
will immediately become evident. 
As I have mentioned the experiments made with heavy 
artillery, as having been led by their results to form important 
conjectures relative to the nature of the expansion of the fluid 
generated in the combustion of gunpowder ; it may perhaps 
be asked, and indeed with some appearance of reason, what 
the circumstances were which attended the experiments in 
question, which could justify so important a conclusion as 
that of the fallacy of the commonly received theory relative 
to that subject. To this I answer briefly, that in regard to 
the supposed instantaneous inflammation of the powder, upon 
which the whole fabric of this theory is built, or rather of all 
the computations which are grounded upon it, a careful atten- 
tion to the phaenomena which take place upon firing off 
cannon, led me to suspect, or rather confirmed me in my 
former suspicions, that however rapid the inflammation of 
gunpowder may be, its total combustion is by no means so 
sudden as this theory supposes. When a heavy cannon is 
fired in the common way, that is, when the vent is filled with 
loose powder, and the piece is fired off with a match, the time 
employed in the passage of the inflammation through the vent 
into the chamber of the piece is perfectly sensible, and this 
time is evidently shorter after the piece has been heated by 
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