Wentworth, G. A. (George Albert), 1835-1906 · Boston, Ginn & company · leaf 370
ion varies slightly according to the condition ofthe atmosphere, but this variation is not taken into account inthis chapter. Dip of the Horizon Let BH (Fig. 38) represent the level of the sea, 0 the posi-tion of the observer at the height BO above the sea level, Cthe centre of the earth, and H the… … CORRECTIONS OF THE OBSERVED ALTITUDE 381 OH will represent the visible horizon. Let OH, perpendicularto OC, represent the true horizon, from which the apparentaltitude of the body isestimated. When we measure thealtitude of S, the sun, wemeasure the angle SOH;but the altitude we re-quire is the…
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