400 PHYSICAL GEOGRAPHY OF THE SKI, AND ITS METEOROLOGY. 



784. So, too, with the West India hurricanes of the Atlantic ; 

 The West India theso winds are most apt to occur during the 

 hurricanes. months of August and September. There is, 

 therefore, this remarkable difference between these gales and 

 those of the East Indies : the latter occur about the changing of 

 the monsoons, the former during their height. In August and 

 September, the south-west monsoons of Africa and the south- 

 east monsoons of the West Indies are at their height ; the agents 

 of one drawing the north-east trade-winds from the Atlantic into 

 the interior of New Mexico and Texas, the agents of the other 

 drawing them into the interior of Africa. These two forces, 

 pulling in opposite directions, assist now and then to disturb the 

 atmospheric equilibrium to such an extent that the most powerful 

 revulsions in the air are required to restore it. " The hurricane 

 season in the North Atlantic Ocean," says Jansen, " occurs simul- 

 taneously with the African monsoons ; and in the same season of 

 the year in which the monsoons prevail in the North Indian 

 Ocean and the China Sea, and upon the Western coast of Central 

 America, all the seas of the northern hemisphere have the hurri- 

 cane season. On the contrary, the South Indian Ocean has its 

 hurricane season in the opposite season of the year, and when the 

 north-west monsoon prevails in the East Indian Archipelago." 



785. Under the head of hurricanes, typhoons, and tornadoes, I 

 Tiie cyclone theory, iucludo all those galos of wiud whicli are known as 

 cyclones. These have been treated of by Red field in America, 

 Eeid in England, Thorn of Mauritius, and Piddington of Calcutta, 

 with marked ability, and in special works. I refer the reader to 

 them. The theory of this school is, that these are rotary storms ; 

 that they revolve against the hands of a watch in the northern, 

 and iviili the hands of a watch in the southern hemisphere ; that 

 nearer the centre or vorte^x the more violent the storm, while the 

 centre itself is a calm, which travels sometimes a mile or two an 

 hour, and sometimes forty or fifty ; that in the centre the baro- 

 meter is low, rising as you approach the periphery of the whirl ; 

 that the diameter of these storms is sometimes a thousand miles, 

 and sometimes not more than a few leagues ; that they have their 

 origin somewhere between the parallels of 10° and 20° north and 

 south, travelling to the westward in either hemisphere, but in- 

 creasing their distance from the equator, until they reach the 

 parallel of 25° or 30°, when they turn towards the east, or 

 *• recurvate," but continue to increase their distance from the 



