A treatise on land-surveying; comprising the theory developed from five elementary principles; and the practice with the chain alone, the compass, the transit, the theodolite, the plane table, &c. Illustrated by four hundred engravings, and a magnetic chart (1875)
Gillespie, W. M. (William Mitchell), 1816-1868 · New York, D. Appleton · leaf 232
ch hold the plates firmly apart, and, bybeing turned in or out, raise or lower one side or the other of theupper plate P, and thereby of the graduated circle. The twoplates are held together by a ball and socket joint. To level theinstrument, loosen the lower clamp and turn the circle till… … ing one in and the other out, as shown by the aiTOws in the figures.A rule easily remembered is that both thumbs must turn in, or bothout. The movements represented in the first of these figures wouldraise the left-hand side of the circle and lower the right-hand side,xhe movements of the second…
Surveying
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