A treatise on levelling, topography, and higher surveying (1876)
Gillespie, W. M. (William Mitchell), 1816-1868, Staley, Cady, b. 1840, ed · New York, D. Appleton and company · leaf 42
(41.) Troughtons Level. In this the bubble-tube is perma-nently fastened in the top of the telescope-tube. It is adjusted 24 LEVELLING, TOPOGRAPHY, AND HIGHER SURVEYING. by the peg method, or some similar one, the cross-hairbeing moved up or down until the observation gives the truedifference of…
Surveying
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