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height of 3-4 feet, and closed on the two other sides like ordinary forging hearths. The hearth and cavity (crucible) are formed of a mixture of fire-proof clay, charcoal and buck-ashes. The tube of a pair of bellows is inserted into one of the sides of the furnace at some small distance above the bottom. The powdered roast slag, either mixed or not with loam or silica, is put into this furnace on the ash-earth, the whole covered with charcoal, and heated until the mass is in a state of fusion. The melted black metal, consisting chiefly of sulphide of iron with sulphide of copper is received in the cavity at the bottom. From time to time the silicic iron slag is removed from the surface of the molten metal, the coarse metal is cooled superficially by a little water and taken out of the cavity in the form of discs. In this state it is named Kawado or sheave copper.
3rd.—Calcination of the course metal, fusion with a clay covering, and expulsion of sulphur as sulphurous acid, in order to obtain blistered copper, (Arado.)
The coarse metal of the former operation is now placed with charcoal into cavities (thick crucibles) of fire-proof clay fixed in the bottom of a furnace with square chimnies similar to that already described, and heated. A strong current of air is then directed upon the metal, and the latter is stirred with an iron rod to facilitate the oxidization of the remaining parts of the iron sulphide. The cavity is then covered with a thick plate, made from fire-proof clay and sand. The joints are plastered with a mixture of clay and buck-ashes, and, after drying, the whole is heated strongly. The remainder of the iron is absorbed as oxide by the slag, the latter being produced by the clay and buck-ashes of the covering plate and cavity. The temperature is raised gradually until the heat is as intense as possible and the metal commences—as the Japanese say—“to boil.” This ‘boiling’ is caused by the action of oxide of copper upon sulphide of copper in a strong heat. By this action metallic copper and sulphurous acid gas are formed, the latter escaping with violent ebullition from the molten mass. After the ebulli-
