PROFESSOR OLMSTED'S OBJECTIONS. 449 



of accounting more particularly for hail, than the original 

 author of the theory had done. And though I am aware 

 that the strength of my theory does not depend on the weak- 

 ness of any other, I think it proper to give the Professor's 

 remarks a passing notice. 



" We assign," says Mr. Olmsted, " as the cause of hail 

 storms, the congelation of watery vapor of a body of warm 

 and humid air, by its suddenly mixing with an exceedingly 

 cold wind, in the higher regions of the atmosphere. Let us 

 examine," says he, " the effects which would result from the 

 meeting of two opposite winds, at the height of 10,000 feet, 

 during the heat of summer, the one blowing from the lati- 

 tude of 30, or from the confines of the torrid zone, and the 

 other from the latitude of 50, or the northern part of British 

 America. If they had equal velocities, they would meet at 

 the parallel of 40; and, as in the case of the Gulf stream, 

 a fluid does not readily change its temperature, merely by 

 flowing through a body of the same fluid of a different tem- 

 perature, and especially air through air, each current would 

 retain nearly its original temperature. 



11 The southerly wind, blowing from a point which is still 

 2000 feet below the line of perpetual congelation, is com- 

 paratively warm, while the northern, coming from a point 

 4000 feet above the same boundary of the empire of frost, 

 will have a degree of cold probably surpassing any with 

 which we are acquainted. We infer from our preliminary 

 principles, that immediately on meeting, the watery vapor 

 of the wanner would be frozen with an intensity corres- 

 ponding to the temperature of the colder current ; that the 

 minute hail stones thus formed and endued with such ex- 

 cessive cold, would begin to descend, and accumulate to a 

 size proportionate to the intensity of the cold of the nu- 

 cleus, and to the space through which they descended, and 

 to the humidity of the lower strata of the atmosphere ; 

 that is, the colder they were when they began to fall, the 

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