. Annual report of the Board of Regents of the Smithsonian Institution. Smithsonian Institution; Smithsonian Institution. Archives; Discoveries in science. 306 THE ELECTRIC FURNACE. retort or crucible lined throug'hout with car])on C, forminj^ one elec- trode, the other being a massive carbon block of rectang-idar section B, which is supported at the center of the retort, and is of such dimensions that its corners approach very closely to the inner carbon walls of that vessel. The raw material is fed in at hoppers on either side of B, their position being- indicated by the circles a and h. Whi
. Annual report of the Board of Regents of the Smithsonian Institution. Smithsonian Institution; Smithsonian Institution. Archives; Discoveries in science. 306 THE ELECTRIC FURNACE. retort or crucible lined throug'hout with car])on C, forminj^ one elec- trode, the other being a massive carbon block of rectang-idar section B, which is supported at the center of the retort, and is of such dimensions that its corners approach very closely to the inner carbon walls of that vessel. The raw material is fed in at hoppers on either side of B, their position being- indicated by the circles a and h. While working the crucible and its contents revolve, thus constantly bring- ing fresh portions of the mass within the zone of activity, while by a carefully proportioned train of gearing the electrode B is gradually raised at such a rate that its lower extremity is always immersed at a constant deptli in the mass under treatment, Avhile an ingot of finished carbide is graduall}' ])uilt up ])eneath it in the crucible. A series of patents have been recently granted in the United States on electric furnaces for the manufacture of such comminuted products as pigments, al)rasives, oxides, refined metals, and a miscellaneous collection of similar character. The general arrangement consists of an arc or resistance furnace, with which is combined an air blast device, playing either inuiiediately onto the furnace contents or upon the vapors arising from it. An ex- ample will serve to demonstrate the general principle involved. Fig. l-t represents a furnace of this description, devised by C. S. Lomax and patented as recently as March, 1902. It is intended for the manufac- ture of the various couunercial oxides of lead and tin. A refractory l)lock F has a narrow channel <• cut in its upper surface; this constitutes the hearth of the furnace, and is of uniform cross section for about the center third of its length. At each extremity it merges into a deeper and wider wedge-shaped cavity,
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