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 109
e second set of lines, or the thalwegs, are the con-verse of the former. They are indicated by the water-courseswhich follow them or occupy them. They are the lines ofgreatest slope when looked at from above, and of least slopewhen looked at from below. They are the lines of greatestzenith distance… … The general system of the surface of a country is mosteasily characterized by putting down these two sets of lines,and marking the changes of slope, especially the beginningand the end. The most important points to be determined are: 1. At the top and bottom of slopes. 2. At the changes of slopes…
Surveying
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