STOIC VIEW 293 



in a moment, sometimes compressing the air, which 

 is forced into a glow ; it is a miracle all the 

 same. Yes, and is not sometimes a gulf opened 

 in the ether, which seems to retire on all sides, with 

 a great glare of light in the hollow centre ? You 

 are ready to cry out. What is this ? 



... I see the very centre of heaven open, 

 And the stars wandering in the sky. . . . 



These stars sometimes do not wait for night to 

 show their light, but burst out in the full light 

 of day. The reason, however, for the stars show- 4 

 ing at a time not their own is different from 

 that alleged ; it is well known that they are there 

 all the time, though hidden. Many comets, too, 

 we cannot see because they are obscured by the 

 sun's rays. Posidonius, in fact, tells us that during 

 an eclipse of the sun a comet once appeared which 

 the sun's proximity had hitherto concealed. Often, 

 when the sun has just set, straggling fires l 

 are seen close to him. No doubt the nucleus of 

 the comet is bathed in sunlight, and therefore 

 cannot be discerned ; but the tail escapes the effect 

 of the sun's rays. 



XXI 



OUR Stoic friends, therefore, are satisfied that, like i 

 trumpet meteors and beams, and other portents 

 of the sky, comets are formed by dense air. They 

 appear in greatest number toward the north, be- 

 cause there is most of the sluggish air there. Why, 

 then, you naturally ask, does the comet not remain 

 stationary, but advance in the sky from day to 

 day ? Let me explain. The comet, according to 



1 I.e. the tail of a comet. 



