C 440 ] 
the fame Nature with Air, and conceives them to be 
fitly defigned by the fame Name. ' 
But fo perfecl a Congruity between thefe fadlitious 
Fluids and Air is not neceffary for the Purpofes of 
this Treatife. The fundamental Politions of this 
Firft Chapter fuppofing no more, than that the Eladi- 
city of the Fluid produced in the Explofion of Gun- 
powder is always, ceteris paribus , as its Denfity ; 
and that the Force of fired Gunpowder is only the 
Adlion of that Fluid modified according to this Law. 
It has been already mentioned, on what Grounds the 
Firft of thefe Principles hath been affcrted, as con- 
tained in the Third Propofition ; and it remains to 
explain the Reafons urged for the Support of the laft 
in the Eight fucceeding Proportions. 
The Law of the Adlion of this Fluid being deter- 
mined, Two Methods offer themfelves for invefti- 
gating the abfolutc Force of Powder on the Bodies 
it impels before it. The firfi by examining the Quan- 
tity of this Fluid produced by a given Quantity of 
Powder, and thence finding its Eladicity at the In- 
flant of the Explofton 5 the other by determining 
the adlual Velocities communicated to Bullets by 
known Charges, adling through Barrels of different 
Dimenfions. The Firfi is the mod eafy and obvious, 
but the Second the mod accurate Method ; and there- 
fore the Author has feparately purfued each, and he 
has found, that their Concurrence has greatly exceeded 
his Expe&ation, and thereby both of them receive 
an additional Confirmation. 
The Quantity of the eladic Fluid, produced by the 
Firing of a given Quantity of Powder, is determined 
by 
