Young, Charles A. (Charles Augustus), 1834-1908, Young, Anne Sewell, b. 1871., ed · Boston, New York [etc.] Ginn and Company · leaf 61
apart from each, other, and cut off their tops at the same level, carefully determined with a surveyors levelling instrument. It will then be found, on sighting across from AtoC (Fig. 15), that the line, after allowing for refraction, passes about eight inches below B, the top of the middle rod.… … Fig. 15. — Curvature of the Earths Surface. Now BA is one mile, and BD equals two-thirds of a foot, oryJ^ of a mile; hence BE equals l2 920 7920 miles. On account of refraction, however, the result cannot be made exact.The necessary correction is large, and varies with the thermometerand barometer…
Astronomy · Constellations
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