THE earth's contour AND SURFACE SUBDIVISIONS. 21 



To appreciate the oceanic basins, we must conceive of the earth without 

 water, — the depressed areas, thousands of miles across, sunk 10,000 to 

 perhaps 30,000 feet below the bordering continental regions, and covering 

 four elevenths of the whole surface. The continents, in such a condition, 

 would stand as elevated mountain plateaus encircled by one great uneven, 

 almost featureless, basin. If the earth had been left thus, with but shallow 

 briny lakes about the bottom, there would have been an ascent of five 

 miles or more from the Atlantic basin to the lower part of the continen- 

 tal plateau, and about five miles more to scale the summits of the loftier 

 mountains of the globe. The continents would have been wholly in the 

 regions of the upper cold, all alpine, and the bottoms of the oceanic 

 basin under oppressive heat, with drought and barrenness universal. The 

 uneven surface of the oceanic basin has been leveled off to a plain by 

 filling it with water. The greatest heights of the world have thereby been 

 diminished more than one half, and genial climates substituted for intol- 

 erable extremes, rendering nearly all the emerged land habitable, and giving 

 moisture for clouds, rivers, and living species. By the same means distant 

 countries have been bound together by a common highway, into one arena 

 of history. 



The calculated mass of the ocean, taking the depth as above given, is 

 1,320,000,000,000,000,000 tons. 



(4) General view of the land. — (a) Position of the land. — The land of 

 the globe has been stated to lie with its mass to the north, about the Arctic 

 pole, and to narrow as it extends southward into the waters of the southern 

 hemisphere ; with the mean southern limit of the continental lands in the 

 parallel of 45°, or just half-way from the equator to the south pole. 



South America reaches to 56° S. (Cape Horn being in 55° 58'), which 

 is the latitude of Edinburgh or northern Labrador ; Africa only to 34° 51' 

 (Cape of Good Hope), nearly the latitude of the southern boundary of 

 Tennessee, and 60 miles nearer the equator than Gibraltar ; Tasmania (Van 

 Diemen's Land) to 43^° S., nearly the latitude of Boston or northern 

 Portugal. 



(&) Distribution. — The independent continental areas are three in num- 

 ber : America, one ; Europe, Asia, or Eurasia, and Africa, a second ; Australia, 

 the third. Through the East India Islands, Australia is approximately con- 

 nected with Asia, nearly as South America with North America through 

 the West Indies ; and, regarding it as thus united, the great masses of land 

 will be but two, — the American, or Occidental, and Europe, Asia, Africa, 

 and Australia, or the Oriental. 



But, further, these great masses of land are divided across from east to 

 west by seas or archipelagoes. The West Indies (between the parallels of 

 10° X. and 30° E".), the Mediterranean (between 30° N. and 45° N.), and the 

 Red Sea, and the East Indies (between 30° N. and 10° S.), with the connect- 

 ing oceans, make a nearly complete band of water around the globe, sub- 



