M. De la Rive on the Formation ofHaiL 295 



must wait till favourable occasions again place us in circumstan- 

 ces where we may see well, and study well, before we propose 

 theories which, like those of Volta, can be supported only upon 

 the reputation of a great name. 



Cleemont, 1.?^ February. 



The account which we have just been reading, and the precise 

 results which the author deduces from the facts of which he was 

 an eye-witness, appear to be of a nature calculated to throw 

 much light on the still rather obscure subject — the formation of 

 hail. As, moreover, they seem to agree with the view we have 

 taken with regard to this phenomenon, we may be allowed, in 

 concluding this article, to explain briefly the opinions which we 

 have formed on the point. 



Electricity, then, always accompanies the formation and fall 

 of hail ; but we are often asked if, in correct reasoning, this is a 

 sufficient motive for admitting that the hail owes its existence 

 directly or indirectly to the electricity : — Is it not possible that 

 the same cause which determines the formation of the hail, at 

 the same time developes the electricity, and that these two phe- 

 nomena, instead of being connected as cause and effect, have no 

 ether alliance than that which depends on their having a com- 

 mon cause.'' The new opinions upon electricity with which 

 science has within these few years been enriched, and more es- 

 pecially those which have obtained concerning the different cir- 

 cumstances in which this element may be developed, seem to 

 confirm this conjecture ; they seem also to derive a new degree 

 of strength from the observations which have been made by M. 

 Lecoq, and we shall therefore endeavour to develope our views. 



The propagation of heat in any body is always accompanied 

 by a development of electricity ; and so far as there is any dif- 

 ference of temperature between the different parts of a body, 

 so far is there a rupture of the natural electrical equilibrium. 

 Now, if we consider a vertical column of atmospheric air dur- 

 ing a serene calm, when no wind or cloud affects its physical 

 condition, it will represent a body in which the temperature 

 goes on decreasing from the base, which rests upon the earth, 

 to its summit, which is the limit of our atmosphere. The 

 difference of the temperature at the two extremes of this 



