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 208
which is an arrow-head or other markon its edge, or the zero-point of a ver-nier scale. There are usually two ofthese, situated exactly opposite to eachother, or at the extremities of a di-ameter of the upper circle, so thatthe readings on the graduated circlepointed out by them differ, if bothare… … 194 LAND-SURVEYING. turn), not being precisely in the center of the graduated circle. Inthe figure, let C be the true center of the graduated circle, but Cthe center on which the plate carrying the indexes turns. LetACB represent the direction of a sight taken to one object,and D C E the direction…
Surveying
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