Not the least of the applications of the dynamo is its use in electro-metallurgy for plating metals, and also for promoting chemical reactions. The electric furnace, stimulated into higher heat by the dynamo than can be otherwise obtained, has brought about many valuable discoveries, and made great advances in various arts. The metal aluminum, and the hard abrasive or polishing and grinding material known as “carborundum” are the products of the electric furnace, and so is the product known as “calcium carbide,” which, when immersed in water, gives off acetylene gas and is a product now universally used for that purpose, and rapidly increasing in commercial importance. [Illustration: FIG. 22.--ELECTROCUTION CHAIR.] In Fig. 23 is seen the Acheson electric furnace for producing carborundum. The electric current traverses the furnace through a series of horizontal electrodes at each end, and highly heats a central core of carbon, which is disposed in a mass of silicious and carbonaceous material, and which latter is converted by the heat into silicide of carbon, or carborundum. In Fig. 24 is shown a continuous electric furnace constructed as a revolving wheel, under the Bradley patents. Rim sections 5 are placed on the wheel on one side and filled with a mixture of carbon and lime, through which the electric current is passed from the dynamo _g_. The heat of the current fuses the mass and converts it into calcium carbide, and as the wheel slowly revolves the rim sections 5 are removed from the opposite side, and the mass of calcium carbide, seen at _x_, is broken off. The electrolytic production of copper through the agency of the dynamo amounts to 150,000 tons annually, and the commercial reduction of aluminum by the electric furnace has grown from eighty-three pounds in 1883 to 5,200,000 pounds in 1898, and its cost has been reduced to about 33 cents per pound. [Illustration: FIG. 23.--PART SECTIONAL VIEW OF CARBORUNDUM FURNACE.] The storage battery, holding in reserve its stored up electric energy, also owes its practical value entirely to the dynamo which charges it, and thus makes available a portable source of supply. [Illustration: FIG. 24.--BRADLEY ELECTRIC FURNACE FOR PRODUCING CALCIUM CARBIDE.]