M. De la Rive on the Formation of Hail. :29S 



mit of Puy-Griou, on account of the violence of the wind. My 

 brother-in-law M. Nivet, who was at the Mont Dore, did not per- 

 ceive the wind at the Pic de Sancy till midday, and I myself, 

 upon the top of Puy-du-Dome, did not perceive its violence till 

 one o'clock, and it was then only that the hail clouds arrived. 



Perhaps I may have dwelt somewhat two much in detail 

 upon these phenomena of which I was an eye-witness, but I be- 

 lieve I have collected some facts which are new to meteorology, 

 a science which is not very rich in them even at the present day, 

 I shall conclude by endeavouring to sum up, without, however, 

 considering them as quite general, the observations which I have 

 collected on the two occasions I have specified. 



Conclusions, 



\st. It appears that hail is formed during the prevalence of 

 winds of impidsioti, and not of those of inspiration^ which, how- 

 ever, are generally more violent than the former. The storm 

 of the 13th July 1788, concerning which M. Tessier made a 

 report to UAcademie des Sciences^ goes to confirm this opinion. 

 Its velocity was nearly the same as that of July 28. 1835. 



2J, Two strata of clouds, placed the one over the other, and 

 two winds from different quarters, seem necessary for the pro- 

 duction of hail. 



3rf, The hailstones do not pass from one cloud to another 

 as Volta supposed ; on the contrary, they advance with very 

 great horizontal rapidity, and are urged forward by an extremely 

 cold wind. 



4^A, Electricity nevertheless plays an important part in these 

 phenomena, and according to all appearance, the superior cloud 

 supports the inferior, heavily loaded with hailstones, and pro- 

 bably in a state of opposite electricity. There is probably also 

 electrical repulsion among the hailstones which form the anterior 

 extremity of the cloud, and which there present the whirlwiiid- 

 like phenomenon which is so remarkable, and which I have twice 

 observed in the most distinct manner, 



5th, The hailstones do not strike against each other during 

 their horizontal transport ; and the noise which is heard, that 



