The theory and practice of surveying. Designed for the use of surveyors and engineers generally, but especially for the use of students in engineering (1886)
Johnson, J. B. (John Butler), 1850-1902 · New York, J. Wiley & sons · leaf 473
ary to elevate it.336. Heliotropes.—When the distance between stationsis such that, owing to the distance, the state of the atmosphere,or the small size of the objective used, a target would appearindistinct, or perhaps not be visible at all, the reflected rays ofthe sun may be made to serve in… … Fig. Fig. 127. shown in Fig. 126 is a telescope mounted with a vertical andhorizontal motion. This is turned upon the station occupiedby the observer, and is then left undisturbed. On the tele-scope are mounted a mirror and two disks^ with circular open-ings. The mirror has two motions so that it…
Surveying
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