ATMOSPHERIC CHANGES. 333 



of an hour. These rapid alternations characterise the elevated 

 plains and paramos of the chain of the Andes. 



The electricity of the atmosphere, whether considered 

 in the lower regions of the air or in the canopy of the clouds, 

 whether studied in its silent problematical diurnal march, or 

 in explosions in the lightning and thunder of the tern- 

 pest, shews itself in manifold relation to the phenomena 

 of the distribution of heat, of the pressure of the atmosphere 

 and its disturbances, of hydro-meteoric phenomena (or 

 watery precipitations), and probably also of the magnetism 

 of the outer crust of the globe. It acts powerfully on the whole 

 animal and vegetable world, not only indirectly through the 

 agency of meteorological processes, the precipitations of 

 aqueous vapour, and the acid or ammoniacal combinations 

 occasioned by it, but also in a direct manner as an electric force 

 stimulating the nerves and promoting the circulation of the 

 organic juices. This is not the place to renew the discussion 

 concerning the proper source of atmospherical electricity when 

 the sky is clear. Its existence has been ascribed, sometimes 

 to the evaporation of impure fluids (impregnated with earths 

 or with salts), ( 409 ) sometimes to the growth of plants, ( 41 ) 

 or to chemical decompositions taking place at the surface of 

 the earth, sometimes to the unequal distribution of heat in 

 the atmospheric strata, ( 411 ) and, lastly, sometimes, according 

 to Peltier's ingenious investigations, to the influence of a 

 constant charge of negative electricity in the terrestrial 

 globe. ( 412 ) The physical description of the universe, 

 limiting itself to the results given by electrometric observa- 

 tions, (particularly those made with the ingenious electro- 

 magnetic apparatus first proposed by Colladon), has only 



