276

BOOK VIII.

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Thuringian pyrites, in which there is gold, sulphur, and vitriol, after the lastparticle of vitriol has been obtained by heating it in water, is thrown into afurnace, in which logs are placed. This furnace is very similar to an ovenin shape, in order that when the ore is roasted the valuable contents may notfly away with the smoke, but may adhere to the roof of the furnace. In thisway sulphur very often hangs like icicles from the two openings of the roofthrough which the smoke escapes.

A —Burning pyre which is composed of lead ore with wood placed above it.B —Workman throwing ore into another area. C —Oven-shaped furnace.

D—Openings through which the smoke escapes.

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If pyrites or cadmia, or any other ore containing metal, possesses a gooddeal of sulphur or bitumen, it should be so roasted that neither is lost. Forthis purpose it is thrown on an iron plate full of holes, and roasted with char-coal placed on top ; three walls support this plate, two on the sides and thethird at the back. Beneath the plate are placed pots containing water, intowhich the sulphurous or bituminous vapour descends, and in the water thefat accumulates and floats on the top. If it is sulphur, it is generally of ayellow colour; if bitumen, it is black like pitch. If these were not drawnout they would do much harm to the metal, when the ore is being smelted.When they have thus been separated they prove of some service to man,especially the sulphurous kind. From the vapour which is carried down, not