CONDITIONS 'OF THE OCEAN FLOOR 155 



the depth may be. At a depth of two miles the pressure 

 is over 300 times as much as at the surface of the water; 

 and here, as we have already found, it is about 15 pounds 

 to the square inch. 



If a bag of air which had a volume of 300 cubic inches 

 at the surface were sunk in the ocean to a depth of two 

 miles, it would have a 

 volume of less than a 

 cubic inch, and the pres- 

 sure upon it would be 

 several tons. It thus 

 happens that deep sea 

 fishes when brought to 

 the surface have the air 

 in their swimming blad- 

 ders so expanded that the 

 bladders are often blown 

 out of their mouths. 



Conditions of the Ocean 

 Floor. The ocean floor 

 is a vast, monotonous, 

 nearly level expanse whose CRINOID 



dreary, slimy, and almost A ^a animal once abundant but now 

 * f found only in deep oceans. 



lifeless surface is enveloped 



in never-ending night and is pressed upon by a vast weight 

 of almost stagnant frigid water. Here and there volcanoes 

 rise upon it with gradually sloping, featureless cones, and 

 sometimes a broad, wavelike swell reaches within a mile or 

 so of the surface. Such a swell extends along the center of 

 the Atlantic Ocean through Ascension Island and the 

 Azores. 



