Chap. 12.] ACCOTJIS-T OF THE WOELD. 41 
mary ; afterwards, when they are in opposition to the sun, 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 
having 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 sta|iion 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 conjunction, 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 sun, and having overtaken 
a straight line passing through the two bodies forms a tangent to the 
smaller orbit. The apparent motion of the planets, sometimes direct and at 
other times retrograde, with their stationary positions, is occasioned by the 
earth and the planets moving in concentric orbits, with different velo- 
cities. One hundred and twenty degrees is the mean distance at which 
the three superior planets become stationary. We have an elaborate 
dissertation by Marcus, on the unequal velocities of the planets, and on 
their stations and retrogradations, as well according to the system of 
Aristotle as to that of Copernicus ; Ajasson, ii. 316 et seq. He remarks, 
and, I conceive, with justice, " .... ce n' est pas dans les traites d'astronomie 
de nos savans que Ton doit puiser les details destines a eclaircir le texte 
des chapitres xii, xiii, xiv et xv du second hvre de Pline Je ne dis 
rien des commentaires de Poinsinet, d'Hardouin et d'autres savans peu 
verses en matiere d'astronomie, qui ont fait dire a Pline les plus grandes 
absurdites." 
^ *' Occasus planetse vespertinus dicitur, quo die desinit post occasiun 
sohs supra horizontem ocuhs se prsebere manifestum ;" 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 other planets become stationary, when at 120 degrees from the 
sun. Mars becomes so at 90 degrees, being detained by the rays, which act 
upon him more powerfully, in consequence of his being nearer to their 
source. 
* I may refer to the remarks of Marcus on the respective distances 
