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 182
also happen that the centre, C, of thesignal cannot be seen from D. Thus, if the sig-nal be a solid circular tower, set the theodoliteat D, and turn its telescope so that its line ofsight becomes tangent to the tower at T, T; T^measure on these tangents equal distances, D E,D F, and direct the…
Surveying
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