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 28
PERPENDICULAR LEVELS. Fig. 8. … will be horizontal. It may therefore be used like any otherline of sight for determining points at the same height as itself. The first form, Fig. 8 (Colonel BureFs), consists of a rhombof lead, of about 2 inches on a side, and 1 inch thick.■ One side (the shaded part of the figure) is faced with…
Surveying
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