Davies, Charles, 1798-1876 · New York, Cincinnati [etc.] American book company · leaf 346
pegs driven into holes drilled for thepurpose. The compass is rarely used for underground work, andought never to be used for any but rough work, because of theinaccuracies to which it may lead. A great deal of the miningin the U. S. is done in the far West, where the magnetic declina-tion is not… … SEC. I.] DEFINITIONS. 339 ployed, and the only necessary one, differs from the ordinarytransit in having a diagonal eye-piece, to permit observations tobe made when the telescope is directed vertically upward, andalso an arrangement for illuminating the cross-wires. A method of lighting the…
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