Chap. 12.] ACCOUNT OF THE "SVOELD. 41 niary ; afterwards, when they are in opposition to the sim, they rise at the distance of 180 degrees from him. And again ad- vancing on the other side to the 120th degree, they attain their evening stations, which are termed secondary, until the sun ha^dng arrived within 12 degrees of them, what is called their evening setting becomes no longer visible ^ Mars, as being nearer to the sun, feels the influence of his rays in the quadra- ture,at the distance of 90 degrees, whence that motion receives its name, being termed, from the two risings, respectively the first and the second nonagenarian^. This planet passes from one station to another in six months, or is two months in each sign ; the two other planets do not spend more than four months in passing from station to station. The two inferior planets are, in like manner, concealed in their evening conjimction, and, when they have left the sun, they rise in the morning the same number of degrees distant from him. After having arrived at their point of greatest elongation^, they then follow the sim, and having overtaken a straight hne passmg through the two bodies forms a tangent to the smaller orbit. The apparent motion of the planets, sometimes dii'ect and at other times retrograde, with their stationary positions, is occasioned by the eartli and the planets moving in concentric orbits, -with diiferent velo- cities. One hmidi-ed and twenty degi'ees is the mean distance at which the three superior planets become stationary. We have an elaborate dissertation by Marcvis, on the unequal velocities of the planets, and on their stations and retrogi-adations, as weU according to the system of Ai'istotle as to that of Coperaicus ; Ajasson, ii. 316 et seq. He remarks, and, I conceive, ^ith justice, ". . . . ce n'est pas dans les traites d'astronomie de nos savans que Ton doit puiser les details destmes a eclaircir le texte des chapitres xii, xiii, xiv et xv du second livre de PUne Je ne dis rien des commentaires de Poinsmet, d'Hardouin et d'autres savans peu verses en matiere d'astronomie, qui ont fait dire a PUne les plus gi'andes absurdites." 1 " Occasus planetae vespertinus dicitur, quo die desmit post occasum Bohs supra horizontem ocuhs se pra?bere manifestmn ;" Alexandre in Lemaire, ii. 265. It is then said to set hehacally. 2 The interpretation of this passage has given rise to much discussion among the commentators and translators ; I may refer the reader to the remarks of Poinsinet, i. 70, 71 ; of Alexandre in Lemaire, ii. 266 ; and of Marcus in Ajasson, ii. 328. I conceive the meaning of the author to be, that while the otherplanets become stationary, when at 120 degi'ees from the sun, Mars becomes so at 90 degrees, being detained by the rays, which act upon him more powerfully, m consequence of his being nearer to their source.
- I may refer to the remarks of Marcus on the respective distances
