294 PHYSICAL SCIENCE BK. vn 



this account, pursues its fuel just as fires do. Al- 

 though its tendency is to rise to the upper regions, 

 still, if material fail it, it retrogrades and sinks. In 

 the air, too, it does not pursue a direct path to right 



2 or left. It has no particular route assigned to 

 it ; wherever the supply of its fuel leads it, thither it 

 crawls ; it does not advance in its orbit as a star, 

 but feeds as a fire. Why, then, does it appear for a 

 long period, and why is it not quickly extinguished ? 

 For the recent one which we saw during this joyous 

 reign of Nero displayed itself to view for six months, 

 revolving in the opposite direction to the former 

 one in Claudius' time. That one rising from the 

 north up toward the zenith made for the east, 

 always growing dimmer. This one began in the 

 same quarter, but making toward the west, turned 

 finally toward the south, where it withdrew from 



3 view. No doubt the former found moister elements, 

 more suitable for its fire, and pursued them ; the latter 

 in turn chose a richer and more substantial district. 

 So they descend toward the direction in which they 

 are invited by their material, and not by a definite 

 path, which in the two we have seen was different, 

 since the one moved off toward the right and the 

 other toward the left. Now all stars 1 have their 

 orbit in one direction, namely, contrary to the motion 

 of the universe. The latter moves from east to 

 west, the stars go from west to east. For this 

 reason they have a double motion, one, their own 

 proper motion ; the other, which carries them round 

 along with the heavens. 



1 Planets may be specially referred to ; the Latin word is the generic one, 

 stella. 



