XVIII.] LAND AND WATER. 



307 



water which covers an area as large as Spain, and has the 

 level of its surface about eighty-three feet below that of the 

 Black Sea ; while the bottom of the hollow in which the 

 water rests falls to about 3,000 feet, or nearly three-quarters 

 of a mile, below the level of the ocean. ' The Caspian itself 

 occupies the deepest part of an enormous depression, which 

 appears to have been connected, at a late geological period, 

 with the Mediterranean Sea. This great basin, which also 

 includes the inland sea of Aral, covers an area at least as 

 large as Central Europe. The Caspian sea alone occupies 

 an area of 126,646 square miles (I.| nearly). The Dead 

 sea is another salt-lake much below sea-level, its surface 

 being about 1,300 feet below that of the Mediterranean. 



Since water naturally flows towards the lowest accessible 

 level, it is only to be expected that these depressed areas 

 should receive the drainage of the surrounding country. A 

 large number of rivers do, indeed, discharge themselves into 

 these great lakes ; and hence such rivers differ essentially 

 from ordinary rivers, like the Thames, in that they never 

 reach the open sea. Such streams are often called con- 

 tinental rivers, since they are confined to continental areas, 

 and their basins are contained within the land. Thus 

 the Dead sea receives the river Jordan ; the Caspian 

 receives the Ural and the Volga — the latter, by the way, 

 being the longest river in Europe — while the sea of Aral 

 receives the Amu Daria (Oxus) and Sir Daria (Jaxartes) 

 which come down from the high plateau of Pamir in Central 

 Asia. As none of these salt lakes, or inland seas, are in 

 communication with the ocean, the water which is brought 

 down to them by these rivers must be got rid of by evapora- 

 tion ; while the soluble matters, which the rivers dissolve 

 from their drainage-areas, must go on accumulating in the 

 lake. 



X 2 



