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 wliich 

 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 fi'om the 

 sun, Mars becomes so at 90 degrees, being detained by the rays, wliich 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 



