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Phenomena and Causes of Had Storms, 5 



one IS desolated, while another escapes uninjured — and since such 

 apparent exceptions in favor of the utility of hail rods would very 

 naturally be exaggerated, I do not feel warranted in assuming the fact 

 of their efficacy as fairly established.* With regard to the merits of 

 tlie hypodiesis in general, I would offer die following remarks. 



1. Although we can conceive that a portion of the atmosphere, 

 suddenly and highly rarefied by electricity, might produce the de- 

 gree of cold requisite to form hail, yet the possihdhy of an event Is 

 but slight evidence of its reality; and we have here no independent 

 evidence that such a rarefaction does in fact take place; but, on the 

 contrary, we have certain evidence from the concourse of opposite 

 winds, from the density and consequent blackness of the clouds, that 

 a great condensation of air takes place in llie region of the storm. 



2. If hail be produced by electricity in the manner supposed, why 

 is it not a constant associate of thunder storms, since the same causes 

 operate continually ; yet the rare occurrence of hail-storms, as well 

 as their desolating effects, mark them, as out of the common course 

 nature. Why, especially, do not hail storms occur in the torrid zone, 

 where the electricity of the atmosphere is most abundant, and the 

 phenomena of thunder storms the mdst violent and terrible? Not 

 being able tlierefore to satisfy ourselves that hail storms are produced 

 by the agency of electricity, let us inquire, in the second place, zt^Aa^ 

 reason ice have to believe that they oive their origin to the cold op 



THE UPPER REGIONS OF THE ATMOSPHERE. 



It is a weW known fact, that the atmosphere grows continually 

 colder as we recede from the earth, until, ^ at a certain elevation, 

 we reach the temperature of freezing water, called the terra of 

 congelation ; riiat the height of the term of congelation above the 

 surface of the earth varies with the latitude, being greatest at the 

 equator, but coming very near to the earth at the pole ; that Its 

 average height at the equator is about fifteen thousand feet, at 

 the latitude of 30*^ twelve thousand feet, and at the latitude of 

 50^ six thousand ;f that beyond this line of perpetual congela- 

 tion, the reduction of temperature sdll proceeds until it shortly 



* The establishment of Hail Insurance Corapanies, £0 late as the year 1829, indi- 

 cates a want of confidence in this kind of protection. On account of the efficacy of 

 lightning rods, no such companies are needed to secure the public against damages 

 by lightning, 



t Ed. Encyc. "Phys, Geography.' See figure^ page 9, 



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