4 14 Mr. Thompson's Experiments 
light as to be rendered intirely ufelefs : and for fome purpofes it 
feems probable, that it would not be the worfe for being even 
heavier than it is now made. Vents are abfolutely neceffary in 
fire-arms, and in large pieces the windage muff be confiderable, 
in order that the bullets, which are not always fo round as they 
fhould be, may not flick in the bore ; and thofe who have been 
prefent at the firing of heavy artillery and large mortars with 
fhot and fhells, muff have obferved, that there is a fenfible fpace 
of time elapfes between the lighting of the prime and the ex- 
plode n ; and that, during that interval, the fame is continually 
iffuing out at the vent with a hilling noife, and with a prodi- 
gious velocity, as appears by the height to which the (beam of 
fire mounts up in the air. It is plain, that this lofs muff be 
greater in proportion as the fhot that is difcharged is heavier ; 
and I have often fancied, that I perceived a fenfible difference in 
the time that elapfed between the firing of the prime and the 
explofion, when bullets were difcharged, and when the piece 
has been fired with powder only ; the time being apparently 
longer in the former cafe than the latter. 
Almofl all the writers upon gun-powder, and particularly 
thofe of the laff century, gave different recipes for powder that 
is defigned for different ufes. Thus the french authors men- 
tion poudre a moufquet , poudre ordinaire de guerre , poudre de 
chajje , and poudre d' artifice-, all of which are compofed of fait 
petre, fulphur, and charcoal, taken in different proportions. 
Is it not probable, that this variety in the compofition of pow- 
der was originally introduced in confequence of obfervation 
that one kind of powder was better adapted for particular 
purpofes than another, or from experiments made on purpofe 
to afcertain the fadt ? There is one circumftance that would 
lead us to fuppofe that that was the cafe. — - That kind of pow- 
der 
