92 STUDIES OF NATURE. 



On the other hand, Nature frequently employe 

 alfo, the fame means, for producing effects di- 

 rectly contrary. For example, we have feen that, 

 in order to increafe the heat over the lands of the 

 North, and to mitigate it over thofe of the South, 

 fhe made ufe of oppofite colours; fhe produces in 

 both the fame effects, by covering the face of the 

 one and of the other with rocks. Thefe rocks are 

 effentially neceffary to vegetation. I have fre- 

 quently remarked, in thofe of Finland, ftripes of 

 verdure fkirting their bafes to the South ; and in 

 thofe of the Iile of France, 1 have feen fuch ver- 

 dant ftripes on the fide averted from the Sun. 



The fame obfervations may be made in our own 

 climate. Tn Summer, when every thing is parched, 

 we frequently find green herbage under walls 

 which have a northerly afpect ; it difappears in 

 Winter; but then we find it replaced in front of 

 eminences which face fouthward. 



We have already remarked, that the icy Zones, 

 and the Torrid Zone, contain the greateft quan- 

 tity of waters, the evaporation of which equally 

 tempers the violence of the heat and of the cold, 

 with this difference, that the greateft lakes are to- 

 ward the Poles, and the greateft rivers toward the 

 Line. There are, it is admitted, fome lakes in the 

 interior of Africa and of America ; but they are 



placed 



