48 PLTirr's FATTJEAL HISTOET. [Book II. 



extremities of their orbits on either side, the stars are then 

 supposed to have proceeded to their greatest distance ; when 

 they ha;ve been a certain number of degrees within their 

 orbits, they are then supposed to return more rapidly, siQce 

 the extreme point in each is the same. And on this account 

 it is that the direction of their motion appears to be changed. 

 For the superior planets are carried along the most quickly 

 in their evening setting, while these move the most slowly ; 

 the former are at their greatest distance from the earth 

 when they move the most slowly, the latter when they move 

 the most quickly. The former are accelerated when nearest 

 to the earth, the latter when at the extremity of the circle ; 

 in the former the rapidity of the motion begins to 

 diminish at their morning risings, in the latter it begins to 

 increase ; the former are retrograde from their morning to 

 their evening station, while Venus is retrograde from the 

 evening to the morning station. She begins to increase her 

 latitude from her morning rising, her altitude follows the 

 sun from her morning station, her motion being the quickest 

 and her altitude the greatest in her morning setting. Her 

 latitude decreases and her altitude diminishes from her 

 evening rising, she becomes retrograde, and at the same 

 time decreases in her altitude from her evening station. 



Again, the star Mercury, in the same way, mounts up in 

 both directions^ from his morning rising, and having followed 

 the sun through a space of 15 degrees, he becomes almost sta- 

 tionary for four days. Presently he diminishes his altitude, 

 and recedes from his evening setting to his morning rising. 

 Mercury and the Moon are the only planets which descend 

 for the same number of days that they ascend. Venus 

 ascends for fifteen days and somewhat more ; Saturn and 

 Jupiter descend in twice that number of days, and Mars in 

 four times. So great is the variety of nature ! The reason 

 of it is, however, evident ; for those planets which are forced 

 up by the vapour of the sun likewise descend with difficulty. 



CHAP. 15. — GEICEEAL LAWS^ OF THE PLANETS. 



There are many other secrets of nature in these points, as 



1 " utroque mode ; " " latitadine et altitudine ; " Hardouin in Le- 

 maire, ii. 27U. ^ " Catholica." 



