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 110
[Note.—The arrows in the figures indicate the direction in which waterwould run.] (150.) Sketching Ground by Contours. A valuable guide is,the observation that the lines are perpendicular to the water-shed lines and thalwegs. ISTote especially the contour-lines atthe bottoms of hills and ridges,…
Surveying
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