THE SURFACE OF THE EARTH. 



soil, or rocks, are comparatively feeble radiators and stronger 

 reiiectors. The water of the ocean, which covers three-quarters 

 of the terrestrial surface, is touch more uniform in its thermal 

 properties than the land. But even those properties of the ocean 

 are modified by the congelation which takes place on so vast a 

 scale in tne frigid zone. 



All these circumstances combined, and many others which can 

 only be fully understood by a more profound study of physical 

 geography, render the actual climatic phenomena extremely dif- 

 ferent from those which would depend on the latitude alone, and 

 which would be developed on a globe the superficial materials of 

 which would be uniform. 



The departure of the lines of equal, mean, and extreme tem- 

 peratures from the parallels of latitude, has been already ex- 

 plained in our Tract upon Terrestrial Heat, and it will not, 

 therefore, be necessary to insist further upon them here. 



VII. IVDIA. 



184 



