340 ATMOSPHERIC ELECTRICITY. 



It follows, from observations made by M. Peltier,* that during the 

 course of the summer of the year 1835 the greater part of the clouds 

 were electric, and that nearly all of them possessed positive electricity. 

 He found scarcely ten to twelve negative clouds among those which 

 jiassed over his apparatus ; but the case was entirely different in the 

 summer months of the next year, during which M. Peltier continued 

 his observations. The clouds were for the most part neutral, and even 

 among those which he judged were electric, from their ashy color and 

 their jagged and movable edges, most of them left the instruments 

 in complete repose. Those which were electric were nearly all nega- 

 tively so. 



The only inference which can be drawn from the preceding is, that 

 positive clouds are greater in number than negative ones. 



§ III. — Of the formation of electric clouds. 



The formation of electric clouds is a question the solution of which 

 has occupied many philosophers. Some of them, and at their 

 head the illustrious Volta,t have sought to explain it by admitting, 

 as we have already seen, that the positive electricity rises in the latent 

 state with the vapor furnished by the ground, and becomes free 

 again when it is condensed. Such might be the origin of clouds 

 positively electrified as well as of atmospheric electricity. As to the 

 formation of the negative clouds, Volta thought that a cloud strongly 

 positive must exercise an electrical influence on a very feebly electrified 

 cloud lying within its sphere of activity, and consequently produces 

 a decomposition of its natural electricities ; so that if the repelled 

 electricity meets other clouds,, vapors or eminences on the surface of the 

 earth, it will escape and leave the cloud charged with negative elec- 

 tricity. By means of this theory we may explain in a satisfactory 

 manner the strong positive electricity which is observed during fogs 

 and dew, and especially that which is exhibited in the rapid formation 

 of thunder clouds ; but we ha^/e seen that the facts which science pos- 

 sesses in its present state do not favor this theory. 



De Saussurel has advanced the opinion that the clouds perform no 

 other office than that of a conductor, and that the electricity which is 

 perceived at the moment of their passage above an electro-atmospheric 

 apparatus is only that which they derive from the higher strata of the 

 air. He was led to this result by an experiment made on the top of 

 Fours, in which he observed that, in throwing into the air during 

 the absence of clouds the small leaden ball of his electrometer, he 

 obtained an electricity equal and even superior to that which those 

 clouds gave in passing above his head. 



M. Gay Lussac§ supposes that the electricity is disseminated in 

 the atmosphere, in a tree state, ready to be transferred to the con- 

 ductors which are presented to it, and that it exists in the same quan- 



«- Comptes Eendus, torn. Ill, page 145. 1836. 



f Journal de Physique, torn. XXIII, page 99, 17S5. 



\ Voyages dans les Alpes, torn. II, § 783 and 786, page 194 and 19S, 



§ Aun. de Chimie et de Physique, torn. YIII, page 167. 



