407 



der during the night, or In the morning. Storms 

 at night are peculiar to certain vallies of rivers, 

 that have a particular climate. 



What then are the causes of this rupture of 

 the equilibrium in the electric tension of the 

 air ? of this continual condensation of the 

 vapours into water? of this interruption of 

 the breezes ? of this commencement and dura- 

 tion of the rainy seasons ? I doubt whether 

 electricity have any influence on the formation 

 of vesicular vapours. It is rather the forma- 

 tion of these vapours that augments and modi- 

 fies the electrical tension. To the North and to 

 the South of the equator, storms or great explo- 

 sions take place at the same time in the tempe- 

 rate and in the equinoctial zone. Is there an 

 action that is propagated through the great 

 aerial ocean from the first of these zones to- 

 ward the tropics? How can it be conceived, 

 that, under this zone, where the Sun rises con- 

 stantly to so great a height above the horizon, 

 it's passage through the zenith can have so 

 powerful an influence on the meteorological 

 changes ? I am of opinion, that, no local cause 

 determines the commencement of the rains un- 

 der the tropics ; and that a more intimate know- 

 ledge of the superior currents of air will eluci- 

 date these problems so complicated in appear- 

 ance. We can observe only what passes in the 

 lower strata of the atmosphere. The Andes are 



