Phenomena and Causes of Hail Storms. 245 



FINED CHIEFLY TO THE TEMPERATE ZONES. They rarely oc- 

 cur in any form in the torrid zone * ; and when they do, it is 

 chiefly on high mountains. Hail is indeed frequent in the polar 

 regions ; but it is of the ordinary kind before mentioned, and is 

 therefore not the subiect of our present inquiry. Of all places 

 in the world, the South of France is most remarkable for fre- 

 quent and violent hail storms. During the year 1829, an in- 

 surance company was formed in France for the special purpose 

 of affording protection against their ravages. 



3. The most violent hail storms occur chiefly during 



THE warmer half OE THE YEAR, AND MOST FREQUENTLY IN 

 the HOTTEST MONTHS. 



4. The hail stones that fall during the same storm, 

 are found to be much smaller on the tops of mountains 

 than in the neighbouring plains. 



5. Though hailstones are of various forms, yet they fre- 

 quently EXHIBIT IN the CENTRE A NUCLEUS WHICH IS AVHITE 



AND POROUS, while the other parts consist of concentric layers of 

 ice, either transparent or of an opaque white, or alternately 

 transparent and opaque, 



6. A SHOWER of hail DURING THE WARMER SEASON OF THE 

 YEAR, IS OFTEN FOLLOWED BY COOLER WEATHER ; in Spring 



and autumn particularly, hail is a well known precursor of cold. 

 Whatever may be the. remoter cause of this phenomenon, Ave 

 can be at no loss for the immediate cause, namely, a sudden and 

 extraordinary cold in the region of the clouds, xchere the hail- 

 stones begin to form : Nor can there be any doubt, that the de- 

 gree of cold by which the nucleus is congealed, must be very in- 

 tense, — far below 32°, or the freezing point of water, — since this 

 nucleus, as there is every reason to believe, rolls up to the final 

 size of the hailstone, by congealing upon itself the watery vapour 

 which it meets with in its descent to the earth. But, although 

 the presence of such an intense degree of cold is implied in the 

 formation of hail, yet the great question before us is, zchat is 

 the origin of this cold itself? Among the different supposi- 

 tions which have been made, or which may be made, there are 

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



• Rees says never ; but the Ed. Encyc. Art. Phys. Geog. says, ' at an ele- 

 vation not less than 1500 or '2000 feet.' V.Tilloch's Mag. vol. xliii, p. 191. 



