_Explosives._--The invention of gunpowder is ascribed to the Chinese, and at a period so far back that its origin is buried in antiquity. It is believed to have been known since the time of Moses, something very like it being mentioned in the ancient Gentoo laws of India 1,500 to 2,000 B. C. For many years it was thought that Roger Bacon invented it in 1249, but it is now known that he was only a factor in its development. Most likely the saltpetre of the plains of China came first in accidental contact with the charred embers of a prehistoric fire, and to the observant man the oxygen-giving saltpetre furnished the charcoal with its means of energetic combustion for the first time. Gunpowder consists of about 75 parts of saltpetre (nitrate of potash), 15 of charcoal, and 10 of sulphur, the proportions varying somewhat with the use to which it is to be applied. In ordinary combustion the air supplies the necessary oxygen. In gunpowder the presence of the air is not necessary, as the saltpetre has imprisoned in its composition a large quantity of oxygen which furnishes to the carbon and sulphur the means for its combustion, gasification and enormous expansion. Originally, gunpowder was pulverulent, like that used in fire works, and had but little propelling force. The making of it in grains (“corned”) is ascribed to Berthold Schwarz, a German monk, about 1320, and this, by promoting the rapidity of its burning, added greatly to its effective force, and gave a new impetus to firearms. In the early part of the Nineteenth Century there were but few improvements in either the composition or manufacture of gunpowder. The introduction of the percussion cap, which exploded the charge by a blow, in the place of the old flint lock, was, however, a notable advance. Alexander John Forsyth, a Scotch clergyman, was the first to apply a percussion or detonating compound, as set forth in his British patent No. 3,032, of 1807. The embodiment of such compounds in the little copper caps was made about 1818, and has been claimed by various parties. Manton’s British patent No. 4,285, of 1818, describes a thin copper tube filled with fulminate and struck sidewise by the hammer to explode it. Joshua Shaw took a United States patent on a percussion gun, June 19, 1822, and the copper percussion cap was said to have been introduced in the United States by him in 1842. The embodiment of the charge of powder and ball in brass and copper shells was done in France by Galay Cazalat as early as 1826. Drawn metallic shells were made by Flobert and Lefaucheux, in 1853, and Palmer, in 1854. Drawn copper cartridges with center fire were introduced in the United States, and patented by Smith & Wesson August 8, 1854, No. 11,496, and solid headed shells by Hotchkiss, August 31, 1869, No. 94,210. [Illustration: FIG. 283.--SUBMARINE MINE. CHARGE, 250 POUNDS DYNAMITE.]