Cli. XVI.] WHIRLWINDS AXD CYCLOXES. 301 



and it has long been my opinion that if meteorologists 

 devoted their attention to the smaller eddies that can be 

 looked at from the outside, and their commencement, 

 continuance, and completion watched and chronicled, 

 they could not fail to obtain a large amount of informa- 

 tion to guide them in the study of all cyclonic movements 

 of the atmosphere. 



Unless the smaller whirlwinds are quite distinct from 

 the larger ones in their origin, the theories advanced by 

 meteorologists to account for the latter are certainly un- 

 tenable. According to the celebrated M. Dove, cyclones 



O * / 



owe their origin to the intrusion of the upper counter 

 trade-wind into the lower trade-wind current.* More 

 lately, Prof. T. B. Maury has stated that " the origin of 

 cyclones is found in the tendency of the south-east trade- 



*- V 



winds to invade the territory of the north-east trades by 

 sweeping over the equator into our hemisphere, the 

 lateral conflict of the currents giving an initial impulse 

 to bodies of air by which they begin to rotate." Cyclones 

 having thus originated, Prof. Maury considers that they 

 are continued and intensified by the vapour condensed in 

 their vortex, forming a vacuum, f 



Himiboldt had long ago ascribed whirlwinds to the meet- 

 ing of opposing currents of air. { There is this dynamical 

 objection to the theory. The movements of the air in 

 whirlwinds is much more rapid than in any known 

 straight current, such as the trade winds ; and it is im- 

 possible that two opposing currents should generate 

 between them one of much greater force and rapidity. 



* " Law of Storms," p. 24G. 



f " Quarterly Journal of Science," 1872, p. 418. 



J " Aspects of Mature,'' vol. i. p. 17. 



