vii WIND AS CAUSE OF COMETS 279 



the higher region, and are driven by the north wind 

 toward the more exalted portions of the heavens. 

 But, surely, if the north wind urged them, they 

 would always be borne toward the south, whither 

 this wind urges its course. And yet, as a fact, they 3 

 have had different movements, some to east, others 

 to west, all in a curved path, a direction which the 

 wind could not impart. Besides, if the impulse 

 which produced the comet carried up on high those 

 north winds from the earth, comets would not arise 

 when other winds blew ; yet they do arise. 



VIII 



LET us now refute this other explanation of i 

 Epigenes, for he employs two. He believes that 

 when all the moist and dry exhalations of the earth 

 unite, the mere discord of the different bodies turns 

 the air into whirlwind. Then the force of that wind 

 as it revolves sets fire by its rapid motion to all 

 that it embraces in itself, and raises it on high. The 

 gleam of the fire that is thus extracted remains as 

 long as there is sufficient nutriment ; when the fuel 

 fails, the fire subsides too. Now, one who talks 2 

 thus pays no attention to the nature of the 

 course of whirlwinds as compared with that of 

 comets. The career of the former is swift and 

 violent, more rapid than the winds themselves. 

 But a comet s movement is so gradual as to 

 render imperceptible the space traversed during 

 a day and a night. Besides, whirlwinds have an 

 erratic, disorderly, and, to use a word of Sallust s, 

 eddying, motion. Comets have a regular course, 

 which observes the appointed track. Surely none 



