Mr. Thompson’s Experiments 
Weight of 
the bullet. 
Velocity of 
the bullet.. 
Collective 
preffure. 
Powder 
inflamed. 
85 th exp'. 
90 grs. 
2109 
0,2581 
37 s rs 
86 th 
251 
1430 
o» 33 10 
48 
87 th 
354 
1288 
0,3778 
55 
88 th 
600 
1240 
0,5949 
86 
89 th 
603 
1 224. 
0,5825 
84 
90th 
1184 
1017 
0,/897 
1 14 
9 1 ft 
1754 
893 
0,9020 
13 1 
But there are many reafons to fttppofe, that the diminution 
of the action of the powder upon the bullet, when it is lighter, is 
not fo much owing to the fmallefs of the quantity of powder 
that takes fire in that cafe as to the Vis inert ice of the generated 
fluid.. It is- true, that a greater portion of the charge takes, 
fire when the bullet is heavy than when it is light, as I found 
in the very experiments of which I am now fpeaking ; but then 
the quantity of unfired powder in any cafe was much too final! 
to account for the apparent diminution of the force when light 
bullets were made ufie of. 
If the elaftic fluid, in the action of which the force of 
powder confifts, were infinitely fine, or if its weight bore no 
proportion to that of the powder that generated it ; and if the- 
grofs matter, or caput mortuum y of the powder remained in the 
bottom of the bore after the explofion, then, and upon no- 
Other fuppofition, would the prefiure upon the bullet be in- 
verfely as the fpace occupied by the fluid : but it is evident that 
this can never be the cafe. 
A curious fubject for fpeculation here occurs : how far would 
it be advantageous, were it poflible, to diminifh the fpecific 
gravity of gun-powder 7 and the fluid generated from it, with— 
n out 
