Gunpowder, the oldest of all explosives, has been the subject of many scientific investigations, sup ported by innumerable experiments; but Nature guards her secrets well; and to this day it cannot be said that the cycle of chemical changes brought about by the combustion of gunpowder is thoroughly understood. Its original components vary, but are generally about 75 parts potassium nitrate, 15 parts carbon, and IO parts sulphur, with other ingredients some times added. These materials, when simply mixed together, burn with considerable vigour, but cannot rank as an explosive until they have been thoroughly incorporated, so that the different molecules are brought into such close proximity that each finds a neighbour ready and willing to combine on the smallest encouragement.