246 Phenomena and Catises of Hail Storms. 



nerated hy the immediate agency of' electricity ; the other, that 

 it is derived from the region of perpetual congelation. 



In the first place, what reason have we to believe, that ike 

 cold which produces hail is generated by the agency o/'electri- 

 ciTY ? Were we to confine our attention to the whimsical rea- 

 sons, or to the gratuitous assumptions, on which most writers up- 

 on electricity proceed, in ascribing to it the power of producing 

 such an extraordinary degree of cold, we should conclude at 

 once that the hypothesis was without foundation *. But it is 

 still proper to inquire if we cannot discover a connexion between 

 some known property of electricity, and the sudden production 

 of an intense degree of cold. It is a known property of electri- 

 city, to rarefy air, and rarefaction produces cold. When we 

 strongly electrify a Leyden jar, the air is frequently so much 

 rarefied as to rush out from any opening in the cover with a 

 hissing noise. In like manner, the air which supports and en- 

 velops thunder clouds, being strongly electrical, might be con- 

 ceived to be powerfully rarefied, and the temperature propor- 

 tionally reduced. The power of a sudden rarefaction of the. air 

 to precipitate in the form of hail, the moisture contained in it, is 

 strikingly exemphfied in the apparatus employed for raising wa- 

 ter at the mines of Chemnitz in Hungary. The only point to 

 be attended to at present is, that a quantity of air previously 

 confined under the pressure of a coliunn of water 1 36 feet in 

 height, is suddenly permitted to escape, and has its temperature 

 so much reduced by the enlargement of the volume, that tlie 

 moisture present falls in a shower of hail f. 



Another argument in favour of the supposition that hail owes 

 its origin to electricity, is derived ftom the protection against 

 hail-storms alleged to be afforded to vineyards in France, and 

 the neighbouring countries, by erecting among them long 

 pointed poles, or hail-rods (paragreles) as they are called. 

 Could the fact be fairly established that places furnished with 



• See, especially, Priestly's History of Electricity, p. 371 — Malte Brun, 

 Phys. Geogr. Vol. I Van Mons, in Nicholson's Phil. Jour, xxiv, 106. 



f Lib. Useful Knowl. Art. ' Hydraulics,' p. 18. The same views with re- 

 spect to the origin of tne cold of hail storms are expressed in this Journal, 

 vol. XV ; Morveau also has the same idea. (Journal de Phys. ix, 64). 

 Idem, xxi, 146. 



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