Berry, Arthur,b. 1862 · London, J. Murray · leaf 94
irection of the point r, say from r to r (fig. 22), i.e. by a motion of the equator from tn to tn, its inclination n tm remaining equal to its former amount ntm, The general effect of this change is shewn in a different way in fig. 23, where r r ^= =0= being the ecliptic, a B c d represents the… … Fig. 23.—The precession of theequinoxes. 54 A Short History of Astronomy [Ch. II. The annual motion r t was, as has been stated, estimatedby Hipparchus as being at least 36 (equivalent to onedegree in a century), and probably more. Its true value isconsiderably more, namely about 50. An important…
Astronomy
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