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 121
urn the com-pass half around, and sight to the same object. If the two read-ings do not agree, there is an error of eccentricity, and the arith-metical mean, or half sum of the two readings, is the correct one. In Fig. 140 the line of sight AB is represented as passing to * This is another example… … Fig. 141.
Surveying
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