HAIL. 149 



the regelation, or freezing together, of numerous 

 smaller stones, as follows : 



The excessive fall of small hailstones, that oc- 

 curs towards the close of the storm, often produces 

 heaps of hailstones several feet in thickness. The 

 separate hailstones readily freeze together, and are 

 afterwards cut into smaller masses by the action 

 of the water rapidly draining off the earth. The 

 fragments thus formed, in all probability, give rise 

 to stories of mammoth hailstones. 



The severity of the lightning-flashes, which at- 

 tend nearly all great hail-storms, has led some 

 meteorologists to believe that hail-storms are caused 

 by the presence of an unusual quantity of free elec- 

 tricity in the atmosphere. The electrical theory 

 of hail is, however, at the present, almost entirely 

 discarded, it being now generally recognized that 

 the lightning is the effect of the hail-storm, and 

 not its cause. 



Yolta proposed the following electrical theory 

 for the production of hail. He imagined two 

 approximately parallel clouds near together, the 

 upper cloud formed of snow, and the under cloud 

 of rain. Assuming these clouds to be respectively 

 charged with positive and negative electricity, the 

 particles of snow in the snow-cloud might, he 



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