Page:The Natural History of Pliny.djvu/77

 Chap. 13.] ACCOUNT OP THE WOELD. 43 that of the zodiac, which is situated obliquely between them. And all these things are made evident by the infallible results which we obtain by the use of the compasses Hence the apsides of the planets have each of them different centres, and consequently they have different orbits and motions, since it necessarily follows, that the interior apsides are the shortest. (16.) The apsides which are the highest from the centre of the earth are, for Saturn, when he is in Scorpio, for Jupiter in Yirgo, for Mars in Leo, for the Sun in Gemini, for Venus in Sagittarius, and for Mercury in Capricorn, each of them in the middle of these signs ; while in the opposite signs, they are the lowest and nearest to the centre of the earth". Hence it is that they appear to move more slowly when they are carried along the highest circuit ; not that their actual motions are accelerated or retarded, these being fixed and determinate for each of them ; but because it necessarily follows, that lines drawn from the highest apsis must approach nearer to each other at the centre, like the spokes of a wheel ; and that the same motion seems to be at one time greater, and at another time less, according to the distance from the centre. Another cause of the altitudes of the planets is, that their highest apsides, with relation to their own centres, are in different signs from those mentioned above^ Saturn is in the 20th degree of Libra, Jupiter in the 15th of Cancer, Mars in the 28th of Capricorn, the Sun in the 19th of Aries, Yenus in the 27th of Pisces, Mercury in the 15th of Yirgo, and the Moon in the 3rd of Taurus. The third cause of the altitude depends on the form of the heavens, not on that of the orbits ; the stars appearing to the eye to mount up and to descend through the depth of the air^ AYith this cause is connected that which depends ^ "ratione circini semper indubitata." 2 In consequence of the precession of the equinoxes these points are continually advancing from W. to E., and are now about 30 degrees from the situation they were in when the observations were first made by the modem astronomers. 3 Our author here probably refers to the motions of the planets through their epicycles or secondary cii'cles, the centres of which were supposed to be in the peripheries of the primary circles. See Alexandi-e m Lo- mahe, ii. 270. rw • j "• It is to tliis visible appearance of convexity in the heavens that Ovia