A treatise on surveying, comprising the theory and the practice ; (1887)
Gillespie, W. M. (William Mitchell), 1816-1868, Staley, Cady, 1840- [from old catalog] ed · New York, D. Appleton and company · leaf 211
ained by the parallel plates, and their fourmilled-headed screws, which hold the plates firmly apart, and,by being turned in or out, raise or lower one side or the other ofthe upper plate, and thereby of the graduated circle. The twoplates are held together by a ball-and-socket joint. To level… … them simultaneously and equally, but in contrary directions, screw-ing one in and the other out, as shown by the arrows in the figures.A rule easily remembered is that both thumbs must turn in, orboth out. The movements represented in the first of these figureswould raise the left-hand side of the…
Surveying
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