EITEES AND OCEANS. 89 



a number of lakes of immense extent, deserving well the 

 name of inland seas, and both northern and southern 

 divisions for the great number and extent of their water- 

 courses. The whole of this great tract of land is traversed 

 from end to end by an extensive chain of mountains, the 

 longest in the world; at its southern part it forms the 

 Andes, from which a range is continued through the Isthmus, 

 and onwards to form the Rocky Mountains. In the 

 southern division this immense chain passes on the west 

 side of the land close to the sea, is of great elevation 

 in some parts, has some of the highest mountain peaks 

 in the world, and volcanoes also, the highest being in 

 the Andes (Popocatapetl is about 16,000 feet high) ; but 

 from the western side of the continent the land descends 

 gradually to the eastern. In South America are some of 

 the highest table-lands known, great elevated tracts in 

 connection with the mountain ranges. 



Australia in its interior is but little known, but the whole 

 aspect of the island appears to be flat, and to have but little 

 elevation, while Greenland and the great tracts of the 

 northern regions beyond, deserve more the name of glaciers, 

 being almost entirely a mass of barren rocks and snow. 



The water-courses of these various great tracts of land 

 are all determined by the formation of the surface, but the 

 amount of water which is carried into the oceans by the 

 rivers of any district is always in proportion to the amount 

 of vegetation in that district ; thus in Europe, Asia, and 

 America, the number and extent of these correspond with 

 the great fertility of the soil, while the northern and western 

 part of Africa the Great Desert give off scarcely any of 

 adequate extent, the Nile appearing to receive its supply 

 from the central parts further south. The reason of it is 

 this : wherever there is vegetation, either in the form of 

 grassy prairies or forests, there is also a great reduction of 

 temperature from the radiation and evaporation, and the 

 consequent formation of rain, dew, or snow, which falling on 

 the ground produces streams, &c. 



Excepting the great tracts of land named, and islands too 

 numerous to be mentioned, the whole surface of the earth is 



