PHENOMENA OF HAILSTORMS. 217 ^* 



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mission. The few inhabitants who survived this cruel epi- 

 demic, removed to the village of Carichana. It was at Pa- 

 raruma, that, according to the testimony of Father Roman, 

 hail was seen to fall during a great storm, about the middle 

 of the last century. This is almost the only instance of it 

 I know in a plain that is nearly on a level with the sea; 

 for hail falls generally, between the tropics, only at three 

 hundred toises of elevation. If it form at an equal height 

 over plains and table-lands, we must suppose that it melts 

 as it falls, in passing through the lowest strata of the atmo- 

 sphere, the mean temperature of which is from 27*5 to 24 

 of the centigrade thermometer. I acknowledge it is very 

 difficult to explain, in the present state of meteorology, why 

 it hails at Philadelphia, at Rome, and at Montpelier, during 

 the hottest months, the mean temperature of which attains 

 25 or 26 ; while the same phenomenon is not observed at 

 Cumana, at La Guayra, and in general, in the equatorial 

 plains. In the United States, and in the south of Europe, 

 the heat of the plains (from 40 to 43 latitude) is nearly 

 the same as within the tropics ; and according to my re- 

 searches the decrement of caloric equally varies but little. 

 If then the absence of hail within the torrid zone, at the 

 level of the sea, be produced by the melting of the hail- 

 stones in crossing the lower strata of the air, we must 

 suppose that these hail-stones, at the moment of their for- 

 mation, are larger in the temperate than in the torrid zone. 

 AVe yet know so little of the conditions under which water 

 congeals in a stormy cloud in our climates, that we can- 

 not judge whether the same conditions be fulfilled on the 

 equator above the plains. The clouds in which we hear the 

 rattling of the hailstones against one another before they 

 fall, and which move horizontally, have always appeared to 

 me of b'ttle elevation ; and at these small heights we may 

 conceive that extraordinary refrigerations are caused by the 

 dilatation of the ascending air, of which the capacity for 

 caloric augments; by currents of cold air coming from a 

 higher latitude, and above all, according to M. Gay Lussac, 

 by the radiation from the upper surface of the clouds. I 

 shall have occasion to return to this subject when speaking 

 of the different forms under which hail and hoar-frost appear 

 on the Andes, at two thousand and two thousand six nun- 



