342

BOOK VIII.

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A —Sieve. B— Tub. C—Water flowing out of the bottom of it. D —StrakeE —Three-toothed rake. F —Wooden scrubber.

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earth or sand is found on the slopes of mountains or hills, or in the level fieldswhich are either devoid of streams or into which a stream cannot be diverted,miners have lately begun to employ the following method of washing, evenin the winter months. An open box is constructed of planks, about sixfeet long, three feet wide, and two feet and one palm deep. At the upperend on the inside, an iron plate three feet long and wide is fixed, at a depthof one foot and a half from the top ; this plate is very full of holes, throughwhich tin-stone about the size of a pea can fall. A trough hewn from a treeis placed under the box, and this trough is about twenty-four feet long andthree-quarters of a foot wide and deep ; very often three cross-boards areplaced in it, dividing it off into compartments, each one of which is lowerthan the next. The turbid waters discharge into a settling-pit.

The metalliferous material is sometimes found not very deep beneaththe surface of the earth, but sometimes so deep that it is necessary to drivetunnels and sink shafts. It is transported to the washing-box in wheel-barrows, and when the washers are about to begin they lay a small launder,