ATMOSPHERIC ELECTRICITY. 335 



an evidence of the frequency of aqueous precipitation^ in like 

 manner as do the frequent mists with which the lovely pla- 

 teau of Bogota is covered. Mists arise and disappear several 

 times in the course of an hour in such elevations as these, and 

 with a calm state of the atmosphere. These rapid alterna 

 tions characterize the Paramos and the elevated plains of thg 

 chain of the Andes. 



The electricity of tlie atmosphere, whether considered in 

 the lower or in the upper strata of the clouds, in its silent 

 problematical diurnal course, or in the explosion of the light- 

 ning and thunder of the tempest, appears to stand in a mani- 

 fold relation to all phenomena of the distribution of heat, of 

 the pressure of the atmosphere and its disturbances, of hydro- 

 meteoric exhibitions, and probably, also, of the magnetism of 

 the external crust of the earth. It exercises a powerful in 

 fluence on the whole animal and vegetable world ; not mere- 

 ly by meteorological processes, as precipitations of aqueous va- 

 por, and of the acids and ammoniacal compounds to which it 

 gives rise, but also directly as an electric force acting on the 

 nerves, and promoting the circulation of the organic juices. 

 This is not a place in which to renew the discussion that has 

 been started regarding the actual source of atmospheric elec- 

 tricity when the sky is clear, a phenomenon that has altern 

 ately been ascribed to the evaporation of impure fluids im- 

 pregnated with earths and salts,* to the growth of plants,t or 

 to some other chemical decompositions on the surface of the 

 earth, to the unequal distribution of heat in the strata of the 

 air,$ and, finally, according to Peltier's intelligent researches, § 

 to the agency of a constant charge of negative electricity in 

 the terrestrial globe. Limiting itself to results yielded by 

 electrometric observations, such, for instance, as are furnished 

 by the ingenious electro-magnetic apparatus first proposed by 

 Colladon, the physical description of the universe should 

 merely notice the incontestable increase of intensity in the 

 general positive electricity of the atmosphere, 11 accompanying 

 an increase of altitude and the absence of trees, its daily va- 

 riations (which, according to Clark's experiments at Dublin, 



* Regarding the conditions of electricity from evaporation at high 

 temperatures, see Peltier, in the Annalcs de Chimie, t. Ixxv., p. 330 



t Pouillet, in the Annates de Chimie, t. xxxv., p. 405. 



t De la Rive, in his admirable Essai Hislorique sur V Elect riciU, p, 

 140. 



$ Peltier, in the Comptes Rendus de VAcad. des Sciences, t. xii.. p 

 207; Becquerel, Traiie de rEieclriciid et dii MagiiHisme, t. iv., p. 107 



11 Diqu-cz. Sui- lEleclriciU de VAir (Bruxel'es^ 1811), p. 56-€l 



