Elementary astronomy; a beginner's text-book (1899)
Holden, Edward Singleton, 1846-1914 · New York, H. Holt and company · leaf 235
ne.—The direction FlG 134 _A Pendttlumup and down, the vertical direction, is at Rest Hangs Ver-defined for any observer by the line TICALLY-in which a pendulum at rest hangs. The pendulum is at-tracted by the whole Earth and if the Earth were a sphereit would always point to the Earths centre. As… … Fig. 135.—A Pendulum at Rest on a Spherical EarthPoints nearly to the Centre of the Earth. never far from that of the Earths radius. (The radius ofthe Earth and the pendulum never make an angle of morethan 12 of arc—a fifth of a degree—with each other.) The zenith of an observer may now be defined…
Astronomy
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