Page:The Natural History of Pliny.djvu/76

i2 pliny's NATUEAL HISTOET. [Book II. him at their morning setting, they become invisible and pass beyond him. They then rise in the evening, at the distances which were mentioned above. After this they return back to the sun and are concealed in their evening setting. The star Venus becomes stationary when at its two points of greatest elongation, that of the morning and of the eveniug, according to their respective risings. The stationary points of Mercury are so very brief, that they cannot be correctly observed. CHAP. 13. — WHY THE SAME STAES APPEAE AT SOME TIMES MOEE LOPTY AND AT OTHEE TIMES MOEE NEAE. The above is an account of the aspects and the occultations of the planets, a subject which is rendered very complicated by their motions, and is involved in much that is wonderful ; especially, when we observe that they change their size and coloiu*, and that the same stars at one time approach the north, and then go to the south, and are now seen near the earth, and then suddenly approach the heavens. If on this subject I deliver opinions different from my predecessors, I acknowledge that I am indebted for them to those indivi- duals who first pointed out to us the proper mode of inquiry; let no one then ever despair of benefiting future ages. But these things depend upon many different causes. The first cause is the nature of the circles described by the stars, which the Grreeks term a-psides^, for we are obliged to use Grreek terms, Now each of the planets has its own circle, and this a different one from that of the world^ ; because the earth is placed in the centre of the heavens, with respect to the two extremities, which are called the poles, and also in from the Sim at which Yentis and Mercury become stationary, and when they attain theu' greatest elongations ; Ajasson, ii. 328, 329. According to Ptolemy, Magn. Constr. hb. viii. cap. 7, the evening setting of Yenus is at 5° 40' fi-om the sun, and that of Mercmy at 11° 30'. ^ " ' Ai//js, hgneus rotse ch'culus, ab utttu) necto;" Hederic in loco. The term is employed in a somewhat different sense by the modem astrono- mers, to signify the point in the orbit of a planet, when it is either at the greatest or the least distance from the earth, or the body about which it revolves ; the former being tei'med the apogee, aphehon, or the higher apsis ; the latter the perigee, perhelion, or lower apsis ; Jennings on the Globes, pp. 64, 65. i "mundo."