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 428
ust reach be-tween numbers, on the scale marked L, corresponding to the dif-ference of the heights of the twogiven points—i. e., from 6 to 6, or 7to 7, and so on. The sector is thenset for all the interpolations betweenthese two points. Then note the difference of heightbetween the desired point… … 628. Ridges and Thalwegs. The general character of the sur-face of a country is given by two sets of lines : the ridge-lines, orwater-shed lines ; and the thahvegs or lowest lines of valleys. The former are lines which divide the wrater falling upon them,and from which it passes off on contrary…
Surveying
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