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 434
de. The steeper the slope is, the less lightit receives, in the inverse ratio of its length—i. e., inversely as thesecant of the angle a which it makes withthe horizon, or directly as cos. a. Then theratio of the black to the white is,: : 1 — cos. a : cos. a. In practice, the difference of shade… … Ill ! 639. Shades by Tints. Indian-ink, or sepia, is used. Theshades are put on with proper darkness, according to a previouslyprepared diapason of tints. The tints are made light for gentleslopes, and dark for steep slopes, in a constant ratio, a slope of 60°being quite black, one of 30° a tint…
Surveying
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