The advantages of Gunpowder, as a propelling agent, over any other explosive material are, the comparative safety attending its manufacture and transport, and the gradual nature of its decomposition when compared with those materials, such as fulminating gold, silver, mercury, &c. &c. In gunpowder, the force resulting from the rapid evolution of gas in a confined space has sufficient time to overcome the inertia of the projectile, which is not the case with other explosive materials, the conversion of which gaseous products is so instantaneous that nothing can resist the intensity of their explosive action. Other advantages suggest themselves in the use of Gunpowder, such as the comparative cheapness of the ingredients composing it, and the ease with which they may be obtained; for the sulphur and saltpetre are very abundant productions of nature, and the charcoal can be manufactured cheaply and with great facility, and if care is taken in the process of the fabrication of powder, little deterioration will take place on its exposure to heat or moisture. ~Air & Steam as propellants~ Condensed air and steam have been used as propelling agents; but the great inconvenience attending their use quite preclude the possibility of adapting them to war purposes. ~Force of Gunpowder.~ As the force and effect obtained from Gunpowder is the foundation of all other particulars relating to Gunnery, we will briefly consider these points. ~Upon what the action of powder depends.~ The action of Gunpowder is dependent upon a purely chemical process. Mr. Robins proved that the force generated by the combustion of gunpowder, was owing to an elastic gas which was suddenly disengaged from the powder, when it was brought to a certain temperature, and further that this disengaged gas had its elastic force greatly augmented by the heat evolved by the chemical action. ~Ingredients are charged with a large volume of heated gas.~ The propelling power of Gunpowder is dependent on the rapid decomposition of the nitre into its component parts; the oxygen forms carbonic acid with the carbon in the charcoal, and the heat thus generated by ignition changes both this and the nitrogen into a large volume of heated gas. In a mixture of nitre and charcoal alone, the oxidation proceeds with comparative slowness; by the addition of sulphur, an augmentation of combustibility is gained, in consequence of its igniting at a very low temperature; the sulphur, also, by its presence, renders available for the oxidation of the carbon an additional amount of oxygen, viz: that which is united with the potassium, the latter being at once converted into sulphite upon ignition of the powder. ~Weight of gas evolved.~ ~Volume of gas evolved.~ ~Heat of gas evolved.~ ~Pressure of gas generated.~ ~Strength of powder not affected by density of air, but by damp.~