228 THE DEPTHS OF THE SEA. [CHAP., V. 
lat. 82° 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 few 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 Acores. 
The central and southern parts of the Atlantic 
appear to be an old depression, probably at all events 
coveval 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 
