A well-known explosive, consisting of an intimate mixture of nitre, charcoal and sulphur. In the manufacture of gunpowder the ingredients selected must be perfectly pure, and they must be reduced to powder separately. They are then roughly mixed, sprinkled with water, and formed into a cake, which is afterwards broken up, granulated, and separated into classes by sieves or different sizes of mesh. The -violence of the explosive power of the substance is due to the sudden evolution of large quantities of gas. Gunpowder is supposed to have been known to the Chinese before the Christian era, but is believed to have been first used in warfare in the seventh century by the Byzantine emperors in the defence of Constantinople.