In 1846 a new and distinct development in explosives was made in the discovery of gun cotton by Schönbein, and of nitro-glycerine in 1847 by Sobrero. The former is made by the reaction of nitric acid, aided by sulphuric acid, on ordinary raw cotton, which, while changing the physical aspects of the cotton but little, gives to it a terrific explosive energy. Nitro-glycerine is made in a somewhat similar way by treating glycerine with nitric and sulphuric acids. At first it found no practical applications, except as a homœopathic medicine for headache, but about 1864 Nobel commenced its manufacture for explosive uses, and since that time nearly all the great blasting operations have been performed through its agency. Its most familiar form is _dynamite_, or giant powder, Nobel’s patent, No. 78,317, May 26, 1868, which is simply nitro-glycerine held in absorption by some inert granular solid, such as infusorial earth, and is thus rendered safer to handle and more convenient to use. A suggestive application of the terrible power of these explosives is in submarine mines. The instantaneous and dastardly destruction of our battleship, “The Maine,” with 250 of her crew, in Havana harbor, February 15, 1898, by one of these agencies, is a harrowing illustration. Fig. 283 represents one of these submarine mines carrying 250 pounds of dynamite, and Fig. 284 is an instantaneous photograph at the moment of explosion. [Illustration: FIG. 284.--EXPLOSION OF A MINE. BASE OF WATER COLUMN, 100 FEET WIDE, HEIGHT, 246 FEET.] _White gunpowder_, or wood powder, was invented by Captain Schultz, of the Prussian army. It is made by treating granulated wood with a mixture of nitric and sulphuric acids, which, acting upon the cellulose of the wood, convert it into an explosive something of the nature of gun cotton. The grains are afterward saturated with saltpetre. This was patented in the United States June 2, 1863, No. 38,789, and in Great Britain, No. 900, of 1864. Dittmar’s powder is another of the same general nature, covered by United States patents No. 98,854, January 18, 1870; No. 99,069, January 25, 1870, and No. 145,403, December 9, 1873. Among the high explosives of more recent date may be mentioned: _Tonite_ (gun cotton and barium nitrate), British patents No. 3,612, of 1874, and No. 2,742, of 1876. _Rack-a-rock_ (potassium chlorate and nitro-benzene), United States patent No. 243,432, June 28, 1881; British patent No. 5,584, of 1881. _Bellite_ (ammonium nitrate and nitro-benzene), United States patent No. 455,217, June 30, 1891; British patent No. 13,690, of 1885. _Melinite_ (picric acid and gun cotton), British patent No. 15,089, of 1885. _Lyddite_, not patented, but believed to be substantially same as melinite, and containing for its active ingredient picric acid, which is a compound formed by the reaction of nitric acid on carbolic acid.