STORMS, HURRICANES, AKD TYPHOONS. 



403 



will go on. Now it is known that the upper current of air in 

 the United States moves constantly, from a known cause, towards 

 the eastward, probably a little to the south of east ; and as the 

 upmoving column containing the cloud is chiefly in this upper 

 current of air, it follows that the storm-cloud must move in the 

 same direction. And over whatever region the storm-cloud 

 appears, to that region will the wind blow below ; thus the wind 

 must set in with a storm from some eastern direction, and, as the 

 storm-cloud passes on towards the eastward, the wind must change 

 to some western direction, and blow from that quarter till the 

 end of the storm."* 



788. According to Dove's " Law of Rotation," which is said to 

 Dove's law. hold good in the northern hemisphere, and is sup- 

 posed to obtain in the southern also, the wind being N.W. and 

 veering, it ought to veer by W. to S.W., and so on, against the 

 hands of a watch. This " law " is explained thus : Suppose a ship 



•w- 



be in S. lat. off Cape Horn as at a, with a low barometer to the 

 north of her, as at C, where the air ascends as fast as it comes 

 pouring in from all sides. The ship, let it be supposed, is just on 

 the verge of, but exterior to the vortex, or that place where the 

 wind commences to revolve. The first rush of the air at a will 

 he directly for the centre C ; consequently, a ship so placed 



* The Fourth Meteorological Eeport of Prof. James P. Espy ; Senate Doc. 65, 

 3-lth Congress, 3rd session. 



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