A treatise on surveying, comprising the theory and the practice ; (1887)
Gillespie, W. M. (William Mitchell), 1816-1868, Staley, Cady, 1840- [from old catalog] ed · New York, D. Appleton and company · leaf 124
or J of a degree. C isa prism which the observer looks through. The perpendicularthread of the sight-vane, E, and the divisions on the card appeartogether on looking through the prism, and the division with whichthe thread coincides when the needle is at rest, is the bearing *of whatever object the… … 110 LAND-SUE VEYING. prism is mounted with a hinge-joint, D. The sight-vane has afine thread stretched along its opening in the direction of itslength, which is brought to bisect any object by turning the boxaround horizontally. F is a mirror made to slide on or off thesight-vane, E ; and it may be…
Surveying
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