EVAPORATION AND CONDENSATION. 295 



Lat. N. 



Granada 12 126 inches. 



CapeFran9ois 19-46' 120 



Calcutta 22 81 



N. Orleans 30 63 



Philadelphia 39'57' 42 



Rome 41 39 



England (Dalton's mean) 50 31 



Petersburg 59 . . . 13 



The above results are greatly modified by a 

 variety of circumstances, such as prevalent 

 winds, the relative positions of land and sea, 

 mountain ranges, &c. For example, the trade 

 wind which blows constantly from east to west 

 over the atlantic ocean within the tropics, de- 

 posits a far greater amount of rain on the eastern 

 slope of South America, than on its western 

 coast. But in the middle latitudes of the northern 

 hemisphere, where the prevalent wind is from the 

 opposite direction, the case is reversed. Hence 

 the greater amount of rain which falls on the 

 western coasts of Europe and N. America, than 

 in the interior of those continents, being wafted 

 from the Atlantic and Pacific oceans. There is 

 also more rain in mountainous regions than on 

 extensive plains. It has been ascertained, that 

 about double the quantity of rain falls on Mount 

 St. Bernard, that falls at Geneva ; and that the 

 mean annual amount of twenty places in the 

 lower valleys at the base of the Alps, is 58.5 

 inches, according to M. Schow. 



