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copper is also converted into oxide of copper, so that the roasted ore consists actually of a mixture of oxide and sulphide of copper with oxide and sulphide of iron. During the roasting of the ore dense white fumes constantly escape from the furnace. The Japanese are rightly afraid of this poisonous ‘copper smoke,’ and very seldom resort to the place where the copper is burning, so long as they perceive it. It contains arsenionus acid, antimonious oxide, sulphurons acid, sulphuric acid &c., all more or less poisonous substances, which have an intensely destructive effect upon the vegetation of the neighbourhood. When the fire is extinguished and the furnace cooled, the coarse copper slag is taken away to be powdered and to undergo the second operation. In the powdered state it is called Kudzu. It will be remarked that the roasting process of the Japanese is very rough, and constitutes one of the reasons why they do not obtain as much metal out of their ore as would be possible with better system of furnaces.
2nd.—Fusion with silica of the hearth-ash to obtain coarse metal (Kawa-do).
The roasted slag is sometimes mixed with loam or silica containing stone, if the original ore does not already contain a sufficient quantity of quartz or silicial stone. The whole is exposed to a much stronger charcoal fire in order to get the slag fused. The small quantity of oxide of copper in the roasted slag acts upon the sulphide of iron still present in the ore, forming sulphide of copper and oxide of iron. The quantity of oxide of copper in the roast slag is, however, too small to decompose the whole of the sulphide of iron. This excess of the sulphide of iron now combines with the sulphide of copper to form a fusible compound which separates itself from the slag and runs to the bottom of the furnace. The oxide of iron combines with silicic acid and forms a slag.
The furnace for this operation in small and has a peculiar thick round bottom in which a round cavity is made. This cavity is surmounted by a square chimney of bamboo and loam. The chimney is open on two sides up to a
