346 ATMOSPHERIC ELECTEICITY. 



tricity of cascades of water, appear to leave no doubt as to this 

 fact. On accoiintof the electric repulsion of the globe, and the superior 

 positive induction to which the vapor from the surface remains subjected, 

 it preserves its negative state though the first strata of the air in 

 which it is diffused are generally already very humid and conse- 

 quently conductors of electricity ; but the presence of this negative 

 vapor in the air weakens the superior positive, and thus, as M. Peltier 

 remarks, the indication of the electrometer would decrease in the 

 cours^e of the day in proportion to the quantity of the vapor which is 

 eliminated under the contrary tensions of the earth and of space. 

 Such might also be the cause of the daily variations of this instrument 

 if its indications were wholly independent of its electric radiation, 

 and consequently of the conductibility of the air. The primitive 

 vapor while undergoing the commencement of condensation produces 

 at first clouds possessing a feeble negative electricity. According to 

 M. Peltier, these are then subjected to a double electric influence; the 

 one positive, produced by the celestial space, the other negative and 

 produced by the earth ; and as it is under this double influence that 

 the new evaporation takes place, this evidently will produce at first neg- 

 ative vapor, and afterwards positive vapor, which, in its turn, forms 

 clouds possessing electricity of the same kind. But would not the 

 same thing happen supposing the air to be provided with positive 

 electricity, the intensity of which might vary with the height? In 

 this case the cloud might experience the induction of the positive elec- 

 tricity of the strata of the air which are above it, and at the same time 

 that of the electricity of the air situated below it ; on account of the 

 increase of the electric intensity with the height, the first action may 

 be stronger than the second, and supposing the cloud negatively 

 electrified at first, there would also result an accumulation of the nega- 

 tive electricity in its higher strata, while the positive electricity pro- 

 duced by a new decomposition of the natural electricities of the same 

 cloud would be restored in a great measure in its lower strata. In 

 this way the first elastic vapor, produced by a new evaporation, might 

 still be negative, while that which had been last formed might equally 

 become positive. Only if it be admitted that the molecules of the air 

 have a positive electricity which is peculiar to themselves, it will happen 

 that the negative electricity of the primitive vapor may re-combine, in 

 part or in whole, with the positive electricity of the molecules of the 

 air, consequently the cloud formed by their condensation will be found 

 to be positively as well as negatively electrified, or rather be in a neutral 

 state. In every case the first elastic vapor, owing to a new evaporation 

 of this cloud, will be found in a negative state, in consequence of the 

 positive influence of the higher regions of the air. This mode of 

 regarding the formation of the electric clouds explains also the fre- 

 quency of the fogs with which the lower strata containing positive 

 electricity are charged. As for the negative fogs, M. Peltier thought 

 that they are retained in contact with the earth only in consequence 

 of their specific gravity, which prevails over the electric repulsion 

 of the earth, or by the repulsive force due to a current of negative 

 vapor which, according to the same philosopher, travels from the 

 equator to the pole. 



