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 115
helast black. For the intermediate slopes, he makes the whiteto the black in the following proportion : The white : the olack :: 45°— angle of slope : angle of slope. For example, for 30°: light : shade :: 45°- 30° : 30° :: 1 : 2. Hence, the space between the strokes is to their thickness,as 45°… … parallel to the contour-lines, as shown in the upper right-handcorner of Fig. 113—a hill drawn by Lehmanns Method. Fig. 113.
Surveying
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