2 79 
the Force of fired Gunpowder. 
of the elasticity of the generated fluid to its density is very 
different from that which Mr. Robins's theory supposes ; and 
that this ratio increases as the density of the fluid is increased. 
Supposing (what on many accounts appears to be extremely 
probable) that this ratio increases uniformly, or with an 
equable celerity, while the density is uniformly augmented ; 
and supposing farther, that the velocity and limit of its in- 
crease have been rightly determined from the result of the set 
of experiments, table I. which were made with that view ; 
then, from the result of the experiments of which we have just 
been giving an account, (in which 12 grains of powder exerted 
a force equal to 9431 atmospheres), taking these experiments as 
a standard, we can with the help of the theorem (x 1+0 ’ 000/iX — y) 
deduced from the former set of experiments, compute the initial 
force of fired gunpowder, thus : 
The density of the elastic fluid, when 1 2 grains of powder 
are used for the charge, being = 468, it is 468’ ,87a =y = 1479.5; 
and in order that this value of y may correspond with the result 
of the experiment, and be expressed in atmospheres, it must be 
multiplied by a certain coefficient, which will be found by di- 
viding the value of y expressed in atmospheres, as shown by 
the experiment, by the number here found indicating its value, 
as determined by computation. 
It is therefore == 6.3744 for the value of this coeffi- 
cient, and this multiplied into the number 1479.5 gives 9431 
for the value of y in atmospheres. 
Again, the density being supposed = 1000 (or, that the 
charge of powder completely fills the cavity in which it is con- 
fined), in that case it will be iooo 1+0 ‘ 4 —y = 15849; and this 
number being turned into atmospheres by being multiplied by 
