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 201
twoobjects. The great value of this instrument, and the accuracy of itsmeasurements of angles, are due chiefly to two things : to the tele-scope with its cross-hairs, by which great precision in sighting to apoint is obtained ; and to the vernier scale, which enables minuteportions of any arc to be… … and steady motion to the movable parts of the instrument add tothe value of the above. A contrivance for repeating the observa- TEE INSTRUMENTS. 187 tion of angles still further lessens the unavoidable inaccuracies ofthese observations. 285. The Surveyors Transit (Fig. 199). In this instrumentthe…
Surveying
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