A treatise on land-surveying; comprising the theory developed from five elementary principles; and the practice with the chain alone, the compass, the transit, the theodolite, the plane table, &c. Illustrated by four hundred engravings, and a magnetic chart (1875)
Gillespie, W. M. (William Mitchell), 1816-1868 · New York, D. Appleton · leaf 242
19 on the circle, each space of the latter will be =19 X 20 ^ ^^,^ ^^^ ^^^ Vernier will read to 20— 19 = 1. If 40 spaces on the Vernier are equal to 41 on the circle, each 41 X 20 = 20V;andtheVer- space on the Vernier will be =nier will therefore read to 20^ 40 ^ 20 = 30. It wiU be retro-grade. In… … If 60 spaces on the Vernier are equal to 59 on the circle, each 59 X ^0of the former will be = —^-^- = 19 40, and the Vernier bU 236 TRAi\SIT AlVD THEODOLITE SURVEYING. [part iv will therefore read to 20 —19 40 = 20. The foUowmg figureshows such an arrangement. The reading in that position -wouldbe…
Surveying
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