What is (mining) to make a drift; to examine a vein or ledge for the purpose of ascertaining the presence of metals or ores; to follow a vein; to prospect. [U.S.] called?

drift — (mining) to make a drift; to examine a vein or ledge for the purpose of ascertaining the presence of metals or ores; to follow a vein; to prospect. [U.S.]. (Webster's 1913.)

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