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 43
OPOGRAPHY, 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 height of the pegs when the bubble is in thecentre. Then make the Third Adjustment, by means ofthe screws under the telescope. Fig. 26.… … (43.) BourdalouesLevel. This is a modifi-cation of Egaults. Thetelescope carries a steelprism near each end;one of which rests on a knife-edge, and the other on thespherical top of an adjusting-screw. (44.) Lenoirs Level. In this, the telescope carries, at eachend, a steel block, whose upper and…
Surveying
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