126 HURRICANES. SECT. XY. 



along the surface of the globe, so that the direction in which the 

 storm is advancing is quite different from the direction in which 

 the rotatoiy current may be blowing at any point. In the West 

 Indies, where hurricanes are frequent and destructive, they 

 generally originate in the tropical regions near the inner boundary 

 pf the trade-winds, and are caused by the vertical ascent of a 

 column of rarefied air, whose place is supplied by a rush of wind 

 from the surrounding regions, set into gyration by the rotation of 

 the earth. By far the greater number of Atlantic hurricanes 

 have begun eastward of the lesser Antilles or Caribbean Islands. 



In every case the axis, of the storm moves in an elliptical or 

 parabolic curve, having its vertex in or near the tropic of Cancer, 

 which marks the external limit of the trade-winds north of the 

 equator. As the motion before it reaches the tropic is in a 

 straight line from S.E. to N.W., and after it has passed it from 

 S.W. to N.E., the bend of the curve is turned towards Florida 

 and the Carolinas. In the southern hemisphere the body of the 

 storm moves in exactly the opposite direction. The hurricanes 

 which originate south of the equator, and whose initial path is 

 from N.E. to S.W., bend round at the tropic of Capricorn, and 

 then move from N.W. to S.E. 



The extent and velocity of these storms are great ; for instance, 

 the hurricane that took place on the 12th of August, 1830, 

 was traced from eastward of the Caribbee Islands, along the 

 Grulf Stream, to the bank of Newfoundland, a distance of more 

 than 3000 miles, which it passed over in six days. Although 

 the hurricane of the 1st of September, 1821, was not so exten- 

 sive, its velocity was greater, as it moved at the rate of 30 miles 

 an hour : small storms are generally more rapid than those of 

 greater dimensions. 



The action of these storms seems to be at first confined to the 

 stratum of air nearest the earth, and then they seldom appear to 

 be more than a mile high, though sometimes they are raised 

 higher ; or even divided by a mountain into two separate storms, 

 each of which continues its new path and gyrations with increased 

 violence. This occurred in the gale of the 25th of December, 

 1821, in the Mediterranean, when the Spanish mountains and 

 the Maritime Alps became new centres of motion. 



By the friction of the earth the axis of the storm bends a little 

 forward. This causes a continual intermixture of the lower and 



