The Hydrosphere 



Antarctic Oceans untouched. From the surveys that 

 have been made, it has been calculated that the cubic 

 content of the oceans is about fourteen times as great 

 as that of the dry land. 



As a general rule the oceanic areas of the Earth are 

 warmer than the continental areas in the same latitude, 

 but we must not suppose that the whole of the ocean 

 waters are warm. As a matter of fact, the waters of 

 the ocean depths are exceedingly cold, and only the 

 surface waters, as a direct result of the absorption of 

 radiant heat from the sun, are warm. This distribution 

 of temperature has a very important bearing on the 

 distribution of life in the ocean depths. 



In the tropics the surface temperature of the ocean 

 reaches 84 Fahr., but the layer of warm water is not 

 deep, as the following figures relating to the Pacific 

 will show : 



Surface . . . . . .' 8o e -84 



100 Fathoms . V . . -. . 60 



200 . .' V . . 50 



500 . ^ * < ' . -, 42 



1000 . / . ,' ....... ' 36 



Bottom . . '. . , . . 32-33 



The temperature of the waters of the ocean sinks 

 with fair rapidity down to a depth of 500 fathoms, at 

 which the temperature is fairly uniform and about 

 4O-45 Fahr. As we pass still farther downwards, 

 the temperature falls slowly until in the greatest depths 

 it falls below the freezing-point, but as salt water 

 solidifies at a lower temperature than fresh, it still remains 

 in the liquid form. 1 



1 The freezing-point of sea water is 28^ Fahr. 

 45 



