100 PHYSICAL GEOGRAPHY. 



If the Earth be supposed to be divided by the Equator 

 so as to form two hemispheres, the quantity of land in 

 the northern hemisphere will be more than three times 

 that in the southern hemisphere ; which circumstance 

 induced the early mathematicians to imagine that there 

 must be a counterbalancing continent towards the South 

 Pole, but this is far from probable to be the fact. The 

 whole surface of the land, as compared with the surface 

 of the water, is said to be in the ratio of three to ten, or 

 somewhat more than two-thirds of the Earth's surface is 

 covered with water. 



The elevation of the Earth's surface evidently varies 

 in degree; it is therefore divided into high lands and low- 

 lands. In Europe there are too high-lands and one low- 

 land. One of the high-lands rises in Norway, and extends 

 with a little interruption, to the Ural Mountains j the 

 other traverses Spain and Portugal, and includes a great 

 part of France, Germany and Italy, and apart of Turkey, 

 terminating at the Black Sea. America comprises the 

 largest extent of elevated land on the globe. An im- 

 mense range of mountains runs almost uninterruptedly 

 from Berring's Straits to the most southerly part of 

 South America. Another ridge, called the Alleghany 

 and Apalachian mountains, runs nearly parallel with the 

 Stony Mountains to the west of the United States, to 

 which those of Brazil seem to correspond. Thus 

 America may be said to have two high-lands and three 

 low-lands. Asia is also traversed by mountains in a 

 similar manner, so as to form a like division. In Africa 

 thisdivision cannot be so defined, from its central re- 

 gionsbeing so little known. 



The high-lands consist either of mountains, as the Alps, 

 the Andes, &c. j or of extensive tracts of level country 

 called plateaux, as the plains of Mexico and Peru. The 

 interior of Asia also forms an extensive plateau. The 

 low-lands are divided into vales and plains. These plains 

 are sometimes called Steppes in Europe and Asia ; Savan- 

 nahs in North America ; and Pampas in South America. 



ISLANDS. 



Islands may have been formed in various ways. 



