The experiments of Mr. Dalton, confirm the premises of Mr. Robins, that the elasticity of the gases produced from a given quantity of powder, is equally increased by heat and diminished by cold as that of atmospheric air. Hence, as we before remarked, and from direct experiments, he concludes that the elastic fluid produced by the firing of gunpowder, is nearly three-tenths of the weight of the powder itself, which, expanded to the rarity of common air, is about 244 greater than the elasticity of common air, or in other words, than the pressure of the atmosphere. To this, however, must be superadded the increase of expansive power produced by the heat generated, which is very intense. The mere conversion of confined powder into elastic vapour, would exert against the sides of the containing vessel, an expansive force 244 times greater than the elasticity of common air, or, in other words, than the pressure of the atmosphere. If the heat, for the expansion of the gases, should be equal to that of red-hot iron, this would increase the expansion of common air, (and also of all gases) about four times, which in the present instance would be as we stated in the preceding pages, 244 to nearly 1000; so that in a general way it may be assumed, that the expansive force of closely confined powder at the instant of firing, is 1000 times greater than the pressure of common air; and as this latter is known to press with the weight of 14-3/4 pounds on every square inch, the force of explosion of gunpowder is 1000 times this, or 14750 lbs. or about six tons and a half upon every square inch. This enormous force diminishes in proportion as the elastic fluid dilates, being only half the strength when it occupies a double space, one-third of the strength when in a triple space, and so on. There is one more fact worthy of notice, that Mr. Robins found the strength of powder to be the same in all variations of the density of the atmosphere, but not so in every state of moisture, being much impaired by a damp air, or with powder damped by careless keeping, or any other cause; so that the same powder which will discharge a bullet at the rate of 1700 feet in a second in dry air, will only propel it about 1200 feet when the air is fully moist, and a similar difference was observed between dry and moist powder. The sum of these remarks, with the necessary illustrations, may be found in the extract we have given from Gregory's Mechanics. Before we mention the different modes of proving powder, we will offer some remarks respecting the use of sulphur in gunpowder. The conclusions on this head are drawn from the experiments made at Essonne, near Paris.