xvi OTHER MISTAKEN EXPLANATIONS 67 



water in them ; then we squeeze our palms together 

 and squirt out the water like a syringe. Imagine 

 something like this to take place in the clouds. 

 When they are compressed the restricted space 

 drives out the air between them, setting it on fire 

 at the same time, and hurling it forth like a cannon 

 ball. The missiles from our balistae l and scorpions l 

 give forth a loud noise as they are hurled. 



XVII 



A CERTAIN number of writers are of opinion that 

 the air of itself emits a report as it traverses the 

 cold and moist regions. Iron, they point out, when 

 heated cannot be dipped in moisture without noise. 

 A mass of heated metal when plunged in water 

 causes a loud sputtering as it is cooled ; so, 

 according to Anaximenes, air meeting cloud produces 

 peals of thunder ; then as it rushes struggling 

 through the obstructions that bar its way it kindles 

 the flame of lightning merely by its escape. 



XVIII 



ANAXIMANDER refers all the phenomena of thunder 

 to air. Peals of thunder are, he says, the sounds 

 of blows on a cloud. He explains the inequality of 

 the peals by the inequality of the blows. To the 

 question, why it thunders in a clear sky also, he 

 answers that even in absence of cloud the atmo- 

 sphere is shaken and rent by the bursting forth of 

 air. But why is there thunder sometimes and yet 



1 The ancient counterparts of cannon. 



