CAPTAIN NOBLE AND ME. E. A. ABEL ON FIEED GUNPOWDEE. 
103 
Now suppose the charge exploded in the chamber to be increased. In this case, not 
only is the density of the permanent gases increased on account of a larger quantity being 
generated, but the density is still further added to, from the gases being confined in a 
smaller space ; the liquid residue CDHG being increased in a like proportion with the. 
charge (D, in fact, varying as S ^ ), we have 
or if p 0 , & 0 be corresponding known values of jp and &, 
.. Po( l — « S o) s 
V— S 0 !-«&• 
( 3 ) 
In taking the tension of the permanent gases to vary directly as their density, we 
have of course assumed that the temperature, whatever be the value of &, is the same. 
In our experiments the charges exploded have varied in quantity from that necessary 
to fill entirely the chamber to a small fraction of that quantity ; but whatever the charge 
it is obvious that if the vessel be considered impervious to heat (and we have already 
pointed out that only with the lower charges is there a material error due to this hypo- 
thesis), the temperature at the moment of explosion would be the same ; for, as in the 
case of Joule’s celebrated experiment, any heat converted into work by the expansion 
of the gases would again be restored to the form of heat by the impact of the particles 
against the sides of the vessel. 
Returning to (3), the value of the constant a in this equation has yet to be found. If 
from Table VI. we take out a second pair of corresponding values & 15 a is determined 
and will be found =*65, very nearly. Taking a=-65, and from Table VI. or the curve 
Plate 16 taking & 0 =’6, p 0 =14'4 tons, equation (3) becomes 
*= 14 -« 8 rhr W 
Substituting in this equation successively values of § -05, T, T5, &c., we obtain com- 
puted values of », which we compare with those derived directly from observation in 
Table VIII. 
