xxn PRESENCE OF FIRE 71 



heavenly bodies, whose immense power is beyond 

 question. 



XXIII 



PERCHANCE, too, when the wind only blows softly i 

 and exerts no great force, the clouds, wafted against 

 each other, will emit fire strong enough to show a 

 gleam, though not to issue from them. Less force 

 is required for lightning than for the thunderbolt. 

 We found above what a glow the friction of certain 

 woods caused. Now when the air, which is inter- 2 

 changeable with fire, [has been changed in full force 

 into fire and] 1 undergoes friction, it is credible and 

 even probable that fire is struck out, but of an 

 evanescent and transitory character, as it arises 

 from no solid material and has no fuel in which it 

 can lodge. It therefore quickly passes ; its duration 

 is no longer than its route and course ; it has 

 nothing to support it when hurled forth into space. 



XXIV 



BUT how, you ask me, when you philosophers say 

 that it is the nature of fire to rise, does the bolt 

 seek the earth ? Perhaps what you said about fire 

 is not true ? It seems to take its course down as 

 well as up. 



Both my statements, I reply, may be true. Fire 

 naturally does rise and mounts if nothing prevents 

 it, just as water naturally gravitates downwards. 

 But water if affected by a force which drives it 

 uphill is pressed up in the direction from which 

 it was precipitated in rain. In like manner the same 



1 These words seem of more than doubtful genuineness. 



