60 
CAPTAIN NOBLE AND ME. E. A. ABEL ON EIRED GUNPOWDER. 
that employed by Captain Noble in his earlier experiments already alluded to. The 
three kinds of powder experimented with gave results varying between 729 and 891 
calories generated by the combustion of 1 kilogramme of powder. 
In the same * number of the ‘ Comptes Rendus ’ in which De Tkomenec’s memoir is 
given, appears a note by MM. Roux and Sarrau, in which, and in a subsequent notef, 
are determined, with small charges, some of the points to which our own investigations 
have been specially directed. 
MM. Roux and Sarrau have given, for five species of powder, the number of 
calories and volume of gas generated by a given weight of powder, and have from these 
data calculated the temperature of combustion and tension of the gas. 
With one of the powders, representing closely the composition of those chiefly 
experimented with by us, the number of calories and volume of the gas agree nearly 
exactly with the numbers found by ourselves. There is, however, a considerable differ- 
ence in our determinations (both theoretical and experimental) of the tension of the gas 
and also of the temperature of explosion, the temperature being estimated by Roux and 
Sarrau at about 4200° C. and the tension at about 4700 atmospheres. 
We shall return, however, to these points when discussing our own experiments. 
B. OBJECTS OE EXPERIMENTS. 
The chief objects which we had in view in making these investigations were : — 
First. To ascertain the products of combustion of gunpowder fired under circum- 
stances similar to those which exist when it is exploded in guns or mines. 
Second. To ascertain the tension of the products of combustion at the moment of 
explosion, and to determine the law according to which the tension varies with the 
gravimetric density of the powder. 
Third. To ascertain whether any, and, if so, what well-defined variation in the nature 
or proportions of the products accompanies a change in the density or size of grains 
of the powder. 
Fourth. To determine whether any, and, if so, what influence is exerted on the 
nature of the metamorphosis by the pressure under which the gunpowder is fired. 
Fifth. To determine the volume of permanent gases liberated by the explosion. 
Sixth. To compare the explosion of gunpowder fired in a close vessel with that of 
similar gunpowder when fired in the bore of a gun. 
Seventh. To determine the heat generated by the combustion of gunpowder, and 
thence to deduce the temperature at the instant of explosion. 
Eighth. To determine the work which gunpowder is capable of performing on a shot 
in the bore of a gun, and thence to ascertain the total theoretical work, if the bore be 
supposed of indefinite length. 
* Comptes Rendus, tom. lxxvii. p. 138. 
t Ibid. p. 478. 
