What is (a) A wooden tub for washing ores and mineral substances in. (b) A square, hollow place on the back of a calcining furnace, where tin ore is laid to dry called?

vat — (Metal.) (a) A wooden tub for washing ores and mineral substances in. (b) A square, hollow place on the back of a calcining furnace, where tin ore is laid to dry. (Webster's 1913.)

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