348 Phenomena and Causes of Hail Storms. 



since hail storms are often of very limited extent, and of places 

 very near to each other, one is desolated, while another escapes 

 uninjured — and since such apparent exceptions in favour of the 

 utiUty 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 the hypothesis in 

 general, I would offer the following remarks. 



1. Although we can conceive that a portion of the atmo- 

 sphere, suddenly and highly rarefied by electricity, might pro- 

 duce the degree of cold requisite to form hail, yet the possibility 

 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 the 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 of 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 most violent and terrible .? Not being able, therefore, 

 to satisfy ourselves that hail storms are produced by ti;e agency 

 of electricity, let us inquire, in the second place, what reason we 

 have to believe that they owe their origin to the cold of the 



UPPEE REGIONS OF THE ATMOSPHERE. 



It is a well known fact, that the atmosphere grows continual- 

 ly colder as we recede from the earth, until, at a certain eleva- 

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

 term of congelation ; that 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 



• The establishment of Hail Insurance Companies, so late as the 5'ear 

 1829, indicates 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. 



