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 488
V-F THE SEXTANT. 473 then we have : DCE=ADE-DEC DCE = 2(GDE-DEF) DCE = 2DFE. 701. Description of the Sextant (Fig. 520). The frame is usuallyof brass, constructed so as to combine strength with lightness. The Fig. 520. … Sextant. handle by which it is held is of wood. The index-arm is movableabout a pivot in the center of the graduated arc. The index-glassis a small mirror, attached to the index-arm at the pivot, so as tobe perpendicular to the plane of the graduated arc. The horizon-glass on the left in the figure…
Surveying
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