VOL. LXXXVJI.] PHILOSOPHICAL TRANSACTIONS. 15Q 



The principal objects I had in view in the following set of experiments were, 

 first, to determine the expansive force of the elastic vapour generated in the com- 

 bustion of gunpowder in its various states of condensation, and to ascertain the 

 ratio of its elasticity to its density ; and 2dly, to measure, by one decisive experi- 

 ment, the utmost force of this fluid in its most dense state ; that is to say, when 

 the powder completely fills the space in which it is fired, and in which the generated 

 fluid is confined. As these experiments were very numerous, and as it will be 

 more satisfactory to be able to see all their results at one cursory view, I have 

 brought them into the form of a general table. In this table, which does not 

 stand in need of any particular explanation, may be seen the results of all these 

 investigations. The dimensions of the barrel used in these experiments were as 

 follow : Diameter of the bore at its muzzle = 0.25 of an inch. Joint capacities of 

 the bore, and of its vent tube, exclusive of the space occupied by the leathern 

 stopper, = 0.08974 of a cubic inch. Quantity of powder contained by the bar- 

 rel and its vent tube when both were quite full, exclusive of the space oc- 

 cupied by the leathern stopper, 25.641 German apothecary's grains, = 24-|- grains 

 Troy. 



The numbers expressing the charges of powder in thousandth 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 completely. Thus, as the barrel and its vent tube were 

 capable of containing 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 ; 3Q0 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 considerably facilitate the compu- 

 tations necessary in order to ascertain the ratio of the elasticity of this fluid to 

 its density. 



The elastic force of the fluid generated in the combustion of the charge of 

 powder, is measured by the weight by which it was confined, or rather by that which 

 it was just able to move, but which it could not raise sufficiently to blow the leathern 

 stopper quite out of the mouth of the bore of the barrel. This weight in all the 

 experiments, except those which were made with very small charges of powder, was a 

 piece of ordnance, of greater or less dimensions, or greater or less weight, accord- 

 ing to the force of the charge ; placed vertically on its cascabel, on the steel hemis- 

 phere which closed the end of the barrel ; and the same piece of ordnance, by 

 having its bore filled with a greater or smaller number of bullets, as the occasion 

 required, was made to serve for several experiments. 



The weight employed for confining the generated elastic fluid, is expressed in the 



