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 396
rtical line, and sight to the rod held hori-zontally. Not3 where the vertical hair strikes. Then turn the LEVELING LOG ATI OK. 381 head to the other side, so as to invert the position of the eyes, andthen sight again. As before, the mean of the two readings is thecorrect one. 564. Reciprocal… … reading. The difference of the reading and of the height of thecross-hairs gives a difference of height of A and B. Then set upat B, and observe to A, similarly. A new difference of height isobtained. The mean of these two is the correct one. lit. of cross-hairs above peg at A=4,3/ Ht. of…
Surveying
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