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 146
ct in the prolongation of AB casts the ADJUSTMENT, USE, AND CARE OF INSTRUMENTS. II5 ray Be directly down the telescope. The angle formed bythe incident and final reflected ray, Rfe^ is twice the anglesubtended by the plains of the mirrors 6^ ^, as was shown inthe case of the sextant. When the rays… … FiG. 25. bar has come into the position Ca\ making an angle ^(p withits former position ca, since this is an angle in the circumfer-ence. The mirror 55 has also turned through an angle |-0and since it was parallel to the mirror ss in its first position itnow makes an angle y ^ ^ (p with it. The…
Surveying
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