262 Count Rumford’s Experiments to determine 
mined by filling them with mercury, and then weighing in 
air and in water the quantity of mercury required to fill them; 
and the quantity of powder required to fill the barrel and its 
vent tube was determined by computation, from the known 
joint capacities of the barrel and its vent tube, in parts of a 
cubic inch, and from the known specific gravity of the powder 
used in the experiments. 
Thus the contents of the barrel and its vent tube having 
been found to amount to 0.08974, °f a cu ^ic inch, and it hav- 
ing been found that 1 cubic inch of the gunpowder in question, 
well shaken together, weighed just 272.68 grains Troy, this 
gives 24.47 grains Troy (= 25.641 grains, German apothe- 
cary’s weight) for the contents of the barrel and its vent 
tube. 
The numbers expressing the charges of powder in thou- 
sandth parts of the joint capacities of the barrel and of its vent 
tube, were determined from the known quantities of powder 
used in the different experiments, expressed in German apo- 
thecary’s grains, and the relation of these quantities to the 
quantity required to fill the barrel and its vent tube com- 
pletely. 
Thus, as the barrel and its vent tube were capable of con- 
taining 25.641 apothecary’s grains of powder, if we suppose 
this quantity to be divided into 1000 equal parts, this will give 
39 of those parts for 1 grain; 78 parts for 2 grains; 390 for 
10 grains, &c. For it is 25.641 to 1000, as 1 to 39 very 
nearly. 
As this method of expressing the quantities of powder shows 
at the same time the relative density of the generated elastic 
fluid, it is the more satisfactory on that account : it will also 
