ufon Gun-powder , &c. 277 
Secondly, From the remit of all thefe experiments it appears, 
that the effect of placing the vent I11 different portions with 
refpect to the bottom of the chamber is different, in different 
charges ; thus, with 165 grains of powder the velocity of the- 
bullet w r as rather diminifhed by removing the vent from o, or 
the bottom of the bore to 1,32 ; but with 218 grains of pow- 
der the velocity was a little increafed, as was alfo the recoil. 
With 290 grains of powder the velocity was greateft when the ' 
powder was lighted at the vent 1,3 which was near the middle 
of the charge, and rather greater when it was lighted at the 
top, or immediately behind the bullet, than when it was 
lighted at the bottom. And by the recoil it would feem, that 
the velocities of the bullets varied nearly in the fame manner 
when the charge confided of 310 grains of powder. 
With 330 grains of powder, both the velocity and the recoil 
were greater when the powder was lighted at the middle of 
the charge, than when it was lighted at the bottom ; but they 
were leaf! of all when it was lighted near the top. And when 
cm ounce of powder was made ufe of for the charge, its force 
was greateft when it was lighted at the bottom. But the dif- 
ference in the force exerted by the powder which arofe from the 
particular pofition of the vent was in all cafes lo mconfiderable 
(being, ns I have before obferved, lefs than what frequently 
occurred in repeating the fame experiment) that no contdufion 
can be drawn from the experiments, except only this, that any 
given charge of powder exerts nearly the fame force, whatever 
is the pofition of the vent. 
And hence the following practical inference naturally occurs, 
viz. that in the formation of fire-arms no regard need be had to 
any fuppofed advantages that gun-fmiths and others have hi- 
therto imagined were to be derived from particular fituations for 
Vol. LXXI. 2 P .. the 
