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 24
principles: 1. That a line perpendicular to a vertical line is a hori-zontal or level line. 2. That the surface of a liquid in repose is horizontal. 3. That a bubble of air, confined in a vessel otherwise fullof a liquid, will rise to the highest point of that liquid. They will be described in the… … First Method.—Set the levelling instrument over one ofthe points, as A, in Fig. 1 Measure the height of the level 6 LEVELLING, TOPOGRAPHY, AND HIGHER SURVEYING. line above the point. Then direct this line to a rod held onthe other point, and note the reading. The difference of thetwo measurements…
Surveying
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