342 ATMOSPHEKIC ELECTEICiTT. 



he eays, " according to the tension of this electricity, the vapor 

 which rises in the air is electrified positively, negatively, or is found 

 to be in a neutral state, and the clouds to the formation of which 

 it concurs partake of the same electrical state. We cannot deter- 

 mine," he adds, " in what circumstances the vapor is negative, 

 since the tension of the electricity of the earth must vary on ac- 

 count of the nature of the portion of surface where the evaporation 

 takes place. If the liquid which forms the vapor rests on conducting 

 bodies, the negative electricity diffuses itself at a distance; while, if 

 they are bad conductors, it remains in its place, and in this case per- 

 haps it is borne off by the vapor and unites in the formation of nega- 

 tive clouds." 



This theory of M. Becquerel is based on the hypothesis that the 

 water receives positive electricity by being transformed into vapor, 

 and that the same vapor, in certain circumstances, carry off a greater 

 or less portion of the negative electricity of the ground. The first part 

 of this theory is at variance with the experiments of M. Peltier. The 

 second M. Becquerel sought to sustain by observation of the nega- 

 tive electricity of cascades. We are indebted to Tralles* for the first 

 observation of this phenomenon. Finding himself one day in the 

 Alps, opposite the cascade of Standbach, (Staubbach?) near the Sauter- 

 brunnen, he presented his atmospheric electrometer, not armed with 

 the metallic wire, to the fine spray, which resulted from the dispersion 

 of the water. He immediately obtained very distinct signs ot nega- 

 tive electricity. The same effect was exhibited at the cascade of 

 Keichenbach. Volta, a short time after, verified the correctness of this 

 observation not only above the great cascades, but also wherever a fall 

 of water existed, however small provided the intervention of the 

 the wind, caused the dispersion of the drops. The electricity always 

 appeared to him as it did to Tralles, negative. Schiiblerf repeated 

 the same experiments in his journey to the Alps, in 1813. He 

 observed fjirther, that this negative electricity was very strong, since 

 it became perceptible at a distance of 300 feet from the cascade of 

 Eeichenbach, and at a distance of 100 feet his electrometer indicated 

 400, and even 500 degrees. On presenting to the spray a small 

 Leyden phial, armed wifh a point furnished with ignited tinder, it 

 became charged in a few moments, so as to furnish sparks and sensible 

 shocks — a })henomenon which Schiibler did not observe, except in 

 rains, strongly electrified, and during storms. During these experi- 

 ments the sky was clouds. 



The negative electricity found in the dispersion of water has been 

 explained in different ways, Tralles attributed it at first to the fric- 

 tion of the minute dro})S of water against the air ; but soon after he 

 thought with Volta^ that the cause was to be found in the evaporation 

 which the same minute drops experience in falling. It may be said, 

 as to the first manner of interpreting this phenomenon, that if expe- 

 rience shows that the parts of a solid body, like charcoal, reduced to fine 



* Oeuvres de Volta, torn. II, page 239. 



f Journal de Schweigger, torn. IX, page 358. 



