Gregory, (_Treatise on Mechanics, &c._ ii, p. 56) has given a summary of the results of the experiments of Mr. Robins, which we insert verbatim. "To determine the elasticity and quantity of this fluid (the elastic) produced from the explosion of a given quantity of gunpowder, Mr. Robins premises, that the elasticity increases by heat, and diminishes by cold, in the same manner as that of the air; and that the density of this fluid, and consequently its weight, is the same with an equal bulk of air, having the same elasticity at the same temperature. From these principles, and from the experiments by which they are established (for a detail of which we must refer to the book itself,) he concludes that the fluid produced by the firing of gunpowder, is nearly 3/10ths of the weight of the generating powder itself; and that the volume or bulk of this air or fluid, when expanded to the rarity of common atmospheric air, is about 244 times the bulk of the said generating powder. Count Salace in his _Miscel. Phil. Math. Soc. Priv._ Taurin, p. 125, makes the proportion as 222 to 1; which he says agrees with the computation of Messrs. Hawkesbe Amontons, and Belidor. Hence it would follow that any quantity of powder fired in any confined space, which it adequately fills, exerts at the instant of its explosion against the sides of the vessel containing it, and the bodies it impels before it, a force at least 244 times greater than the elasticity of common air, or, which is the same thing, than the pressure of the atmosphere; and this without considering the great addition arising from the violent degree of heat, with which it is endued at that time; the quantity of which augmentation is the next head of Robins's inquiry.