326 PHYSICAL GEOGKAPHY. 



qle uniformity 0.5 Cent. (0.9 Fall.) for one degree of 

 latitude. But as a decrease of temperature of 1.0 Cent. 

 (l.8 Fah.) corresponds to an increase of vertical elevation 

 of 480 to 522 French feet (512 to 556 English), it follows 

 that a difference of elevation of 240 to 264 French 

 feet (256 to 278 English) produces the same effect on the 

 annual temperature as a change of one degree of latitude. 

 The mean annual temperature at the Convent on the Great 

 St. Bernard, at the elevation of 7668 French (8173 English) 

 feet in lat. 45 50', should therefore be found at the level of 

 the sea in lat. 75 50'. 



In that portion of the chain of the Andes which falls 

 within the tropics, observations, made by myself at various ele- 

 vations from the sea-level to a height of 18000 French feet 

 (19185 English), gave a decrease of temperature of lCent. 

 (1.8 Fah.) for 576 French feet (614 English). My friend 

 Boussingault found, as a mean result, thirty years afterwards, 

 540 French feet (575 English). By a comparison of places 

 in the Cordilleras, at equal elevations above the level of the sea., 

 but situated some on the declivities of mountains, and others 

 on extensive table lands, I found that the latter class of stations 

 shewed a higher annual temperature varying from 1.5 Cent. 

 to 3 Cent. (2.7 to 4.2 Fah.) ; and the difference would be 

 still greater if it were not for the cooling effect of nocturnal 

 radiation. As the various climates are here placed successively 

 stage above stage, from the cacao plantations of the lowlands 

 to the limit of perpetual snow, and as the differences of tem- 

 perature in the course of the year are very small, we may^ 

 obtain a tolerably accurate representation of the climates 

 experienced by the inhabitants of the large towns in the 

 Andes, by comparing them with the temperatures of parti- 



