228 THE DEPTHS OF THE SEA. [chap. v. 



lat. 32° 55' N., long. 47° 58' W., indicating a chasm 

 between the coast of America and the Western 

 Islands, which might easily engulph the whole range 

 of the Himalayas. This space probably represents 

 the deepest part of the North Atlantic ; but there is 

 little doubt that these depths are greatly exagge- 

 rated. The average depth of the ocean bed does not 

 appear to be much more than 2,000 fathoms (12,000 

 feet), about equal to the mean height of the elevated 

 table lands of Asia. 



The thin shell of water which covers so much of 

 the face of the earth occupies all the broad general 

 depressions in its crust, and it is only limited and 

 more abrupt prominences which project above its 

 surface as masses of land with their crowning pla- 

 teaux and mountain ranges. The Atlantic Ocean 

 covers 30,000,000 of square miles and the Arctic Sea 

 3,000,000, and taken together they almost exactly 

 equal the united areas of Europe, Asia, and Africa 

 — the whole of the old world ; and yet there seem 

 to be fevf depressions in its bed to a greater depth 

 than 15,000 or 20,000 feet— a little more than the 

 height of Mont Blanc — and except in the neigh- 

 bourhood of the shores there is only one very 

 marked mass of mountains, the volcanic group of 

 the Agores. 



The central and southern parts of the Atlantic 

 appear to be an old depression, probably at all events 

 coseval with the deposition of the Jurassic forma- 

 tions of Europe, and throughout these long ages 

 the tendency of that great body of water has no 

 doubt been to ameliorate the outlines, softening down 

 asperities by the disintegrating action of its waves 



