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 59
en in it, and the FlG 52 tree blazed and marked, as inFig. 52. A stake will do till frost. Bench-marks should be madenear the starting-point of a line oflevels; near where the line crosses aroad ; on each side of a river crossedby it; at the top and bottom of anyhigh hill passed over; and always at… … (61.) Check-Levels, or Test-Levels. No single set of levelsis to be trusted; but they must be tested by another set, runbetween the bench-marks (B. M.s), though not necessarilyover the same ground. THE PRACTICE. ^ A set of levels will verify themselves if they come aroundto the starting-point…
Surveying
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