ATMOSPHERIC ELECTEICITT. 345 



After having established this principle, ^l. Peltier thus explains 

 the electricity of clouds: When the first elastic va})()r charged with 

 negative electricity has been condensed into opaque clouds by being 

 cooled down, and the temperature in rising again afterwards pro- 

 duces a second evaporation, which takes place under a superior 

 positive induction, and the first vapor produced has its negative 

 tension increased, at the expense of the lower strata of cloud, kept 

 at the positive state by terrestrial influence. It follows that the 

 elastic vaj)or produced in the second evaporation is more strongly 

 negative than that first formed, while the vapor produced by the 

 evaporation of the lower strata of the cloud will become positive. 

 When a new lowering of temperature afterwards produces condensa- 

 tion into clouds of the secondary vapor, the higher masses form 

 negative and the lower masses positive clouds, the former keeping 

 tliemselves at a greater elevation than corresponds to their specific 

 gravity, because of the repulsion of the earth, the latter, on the con- 

 trary, descending to a lower level than belongs to their weighton account 

 of the attraction of the globe. This transformation of the elastic into 

 opaque vapor, and of opaque into elastic vapor, alternating a 

 great number of times, according to the atmospheric conditions, 

 ■would result in clouds the electric tension of which may become very 

 powerful. M. Peltier produced an illustration of one of these transforma- 

 tions by making use of a considerable number of very small soap 

 bubbles, which he subjected, in an insulated capsule of glass, to the 

 positive action of a globe ; he saw some of these balls elongate, shoot 

 out, dissolve, and disappear, leaving the rest of the cloud powerfully 

 charged with positive electricity, a phenomenon which indicated that 

 all the parts which rushed out and were dissolved were negative. 



It appears, also, according to the same philosopher, that observations 

 may be made in support of this theory when the sky is sprinkled 

 with cumuli, thin enough to distinguish their interior movements. 

 In examining one of these thin clouds, we see that each of its 

 parts changes its position in relation to the others while the evapora- 

 tion is going on ; and these movements are the more extended the 

 more rapidly the evaporation proceeds, without, however, being the 

 same in tlie whole mass. Toward the edge which receives the direct 

 rays of the sun, the evaporation being greater, the opaque vapor 

 becomes strongly positive, and we see it attracted towards the earth, 

 pass below the mass of cloud, and continue there while on the 

 opposite side the vapor extends and disperses until it is all trans- 

 formed into elastic vapor, but without the great agitation or lively 

 repulsion from above to below. Finally ; after a succession of 

 of warm days, which reproduced a series of transformations of the 

 opaque into elastic vapors, and vice versa, we may sometimes, by means 

 of the kite, reach some of those masses of elastic vapors having an 

 electric tension different from that of the adjacent masses, and strong 

 enough to neutralize the whole positive current produced in the lower 

 strata. 



This explanation of the electricity of the clouds admits that the 

 vapor enters the air charged witli negative electricity. The detail 

 into which we have entered, and the observations on the elec- 



