Phenomena and Causes of Unil Storms. 8 



congealing upon itself the watery vapor which it meets with in Its 

 descent to the earilu But, aliliough the presence of sucli an intense 

 degree of cold is implied in the formation of hail, yet the great ques- 

 tion before us is, what is the origin of this cold itself^ Among the 

 different suppositions which have been made, or which maybe made, 

 there are only two that are worthy of notice. One is, that the cold 

 is generated hy the immediate agfmt^ of electricity ; die other, that 

 it is derived from the region of perpetual congelation. 



In the first place, what reason have ice to believCy that the cold 

 which produces hail is generated hy the agency of electricity? 

 Were we to confine our attention to the whimsical reasons, or to the 

 gratuitous assumptions, on which most writers upon electricity pro- 

 ceed, in ascribing to it the power of producing such an extra- 

 ordinary degree of cold, we should conclude at once that the hy- 

 pothesis 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 electricity, 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 sup- 

 ports and envelops thunder clouds, being strongly electrical, might 

 be conceived to be powerfully rarefied, and tlie temperature pro- 

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

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

 strikingly exemplified in the apparatus employed for raising water 

 at the mines of Cliemnitz in Hungary- The only point to be at- 

 tended to at present is, that a quantity of air previously confined 

 under the pressure of a column of water 136 feet in height, is sud- 

 denly permitted to escape, and has its temperature so much reduced 

 by the enlargement of the volume, that the moisture present falls in 

 a shower of hail.f 



Another argument in favor of the supposition that hail owes its 

 origin to electricity, is derived from the protection against hail-storms 



*See, especially, Priestley's History of Electricity, p. 371 — Malte Brun, Phys. 

 Geogr. Vol I. — Van Mons, in Nicholson's Fhil. Jour. XXIV, 106, 



i Lib. Useful Knowl. Art. * Hydraulics,' p. 18. The same views with respect to 

 file origin of the cold of hail storms are expressed in this Journal, VoL XV. 



Morveau also has the same idea, (fournal de Phys, IX, 64.) Idem. XXI, 146. 



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