Phoiomciia and Causes of Hail Storms. 



9 



clouds and rain and thunder and lightning ; but in this region we 

 know not when to look for thntfreezing current^ unless we ascend so 

 high that there, no hot air exists, holding watery vapor to be frozen 

 by it. The case is plain, that if we ascend in the torrid zone for air 

 that is cold enougli to answer our purpose, we ascend above the re- 

 gion of the hot air, the watery vapor of which Is necessary to afford 

 the materials for hail j whereas, in our own latitude, on ascending to 

 the region of congelation, we find the north and south currents dif- 

 fering in temperature, more than opposite winds in any other part of 

 the globe. There is indeed one situation where we may imagine hail 

 to be formed widiin the torrid zone, and tliat is in the vicinity of lofty 

 mountains covered with snow; and there in fact it does somelimeshail.* 



Next, if we attentively consider the circumstances of the frigid 

 zone, we shall see that here there is no hot region on the one side 

 to send its heated air to mix with the cold currents from the otlier j 

 and that no meeting of very cold with warm winds could possibly 

 take place. The rain indeed, on account of the ordinary cold of this 

 region, would frequently descend in the form of hail j but it would ne- 

 cessarily be of that small and ordinary khid, which is formed near 

 the earth, before described as being common in the polar regions. 



This wuU become obvious by inspecting the following figure. 



c 



90 80 



The curve B, C, D, represents the line of perpetual congelation^ as gjiven in the 

 Edinburgh Encyclopaedia, under the article ** Physical Geography," and is believed 

 to be a very accurate delineation of it. Let then, a a' denote the path described by 

 the opposite winds that are supposed to meet at the latitude of 40^; b ¥^ that of simi- 

 lar winds meeting at the equator, each being at the height of 10,000 feet above the 

 earth ; and c c', the path of two currents at the height of 2,000 iceXy meeting at the 

 latitude of 70'=^. These heights are taken arbitrarily, as affording a favorable view of 

 the nature of our reasoning- The same mode of reasoning, however, tnay be ap- 

 plied to oiher points of elevation, at which any particular hail storm may be supposed 

 to be generated. 



Edin. Encyc, Vol. XV, Art. Phys- Geogr. at an elevation of 1500 or 2000 feet. 



XVIIL— No. 1. 



2 



