xvin CHIEF CAUSE OF EARTHQUAKE 247 



XVIII 



THE chief cause of earthquake, therefore, is air, i 

 an element naturally swift and shifting from 

 place to place. As long as it is not stirred, but 

 lurks in a vacant space, it reposes innocently, 

 giving no trouble to objects round it. But when 

 any cause coming upon it from without rouses it, or 

 compresses it, and drives it into a narrow space, 

 in the first instance, to be sure, it merely retires 

 and roams about, its enclosure. But when oppor 

 tunity of escape is cut off, and resistance meets it 

 on all hands, then 



. . . With deep murmur of the mountain 

 It roars around the barriers ; . . . 



which, after long battering, it dislodges and tosses 

 on high, growing the more fierce, the stronger the 2 

 obstacle with which it has contended. By and by, 

 when it has traversed the whole space in which it 

 was enclosed, and has failed to find a way of escape, 

 it recoils from the side on which its impact was 

 greatest. It is then either distributed through 

 the secret openings which the earthquake of itself 

 causes here and there, or escapes through a new 

 rent. So uncontrollable is this mighty power. No 

 bolt can imprison wind ; it loosens every bond, 

 bears with it every weight, and insinuating itself 

 into the smallest crannies wins its release ; for by 

 the invincible power of nature it is free, especially 

 when roused, and asserts its right for itself. Air is 3 

 a thing no man can tame ; nothing will be found 

 which, 



