Experiments upon Gunpowder. 



79 



the line p m shall be to p I or PL as the force acting 

 upon the bullet in the pointy is to its weight, till p m co- 



incides with Q B, then will the area P M Q B be to the 

 area P L D B in the duplicate proportion of the veloci- 

 ties which the bullet would acquire when acted on by its 

 own gravity through the space P B, and when impelled 

 through the same space by the force of the powder, as 

 may be seen demonstrated by Sir Isaac Newton in his 

 Mathematical Principles of Natural Philosophy, Book 

 I., prop. 39. 



Now what I call the collective pressure, or sum total 

 of the action of the powder upon the bullet, is the meas- 

 ure of the area P M Q B; and it is plain, from what has 

 been said above, that its measure may in all cases be ac- 

 curately determined, when the weight and velocity of 

 the bullet are known. 



If all the powder of the charge were inflamed at once, 

 or before the bullet sensibly moved from its place, and 

 if the pressure of the generated fluid were always as its 

 density, or inversely as the space it occupies, then would 



