BOOK II. xLLx. 131-L. 133 



XLIX. Now as to sudden blasts, which arise as casuai 

 has been said " from exhalations of the earth, and ^i^^onm. 

 fall back again to the earth dra^^ing over it an envelope 

 of cloud ; these occur in a variety of forms. The 

 fact is that their om-ush is quite irregular, Hke that of 

 mountain torrents (as we have pointed out * is the 

 view of certain persons), and they give forth thunder 

 and Hghtning. If travelHng with a heavier momen- 

 tum they burst a great gap in a dry cloud, they 

 produce a storm called by the Greeks a cloudburst ; 

 but if they break out from a dowmvard curve of 

 cloud " with a more Hmited rotation, they cause a 

 whirl unaccompanied by fire — I mean by Hghtning — 

 that is called a typhoon, which denotes a whirHng 

 cloudburst. This brings down with it a portion of 

 heat torn from a cloud, which it turns and whirls round, 

 increasing its own downward velocity by its weight, 

 and shifting from place to place with a rapid whirl ; 

 it is specially disastrous to navigators, as it twists 

 round and shatters not only the yards, but the vessels 

 themselves, leaving only the slender remedyof pouring 

 out vinegar in advance of its approach, vinegar being 

 a very cold substance. The same whirlwind when 

 beaten back by its very impact snatches things up 

 and carries them back with it to the sky, sucking 

 them high aloft. 



L. But if it bursts out of a larger cavern of down- Kinds of 

 ward pressing cloud but not so wide a one as in the «'''*'^"'""^- 

 case of a storm, and is accompanied by a crashing 

 noise, this is what they call a whirlwind, which over- 

 throws everything in its neighbourhood. When the 

 same rages hotter and with a fiery flow, it is caHed 

 a prester, as while sweeping away the things it comes 

 in contact with it also scorches them up. But a 



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