156 THE WATERS OF THE EARTH 



There are no hills and vales, no mountain ranges having 

 sharp peaks and deep valleys. Gradually rising ridges 

 and volcanoes, sometimes topped with coral islands, alone 

 vary the monotony. It is the nether world of gloom and 

 unaltering sameness. Here the derelicts of ages past, after 

 their fierce buffeting with wind and wave, have found a quiet, 

 changeless haven where they may lie undisturbed until 

 absorbed into the substance 4 of the all-enfolding water. 



The Carpet of the Ocean Floor. Near the shore, the 

 floor of the ocean is covered with sand and mud derived 

 from the waste of the land. In the deeper sea the cover- 

 ing is a fine-textured material of animal origin called ooze. 

 It is composed of the shells of minute animals that live 

 near the surface. 



At a depth of about 3000 fathoms (18,000 feet) these 

 shells disappear and a reddish clay appears. This clay is 

 believed to be due to meteoric and volcanic dust and to 

 the insoluble parts that remain after the calcareous (lime- 

 like) material of the minute shells has been dissolved in 

 sinking through the deep water. No layers of this kind 

 have ever been found on the land, and this is one of the 

 reasons for believing that the depths of the sea have never 

 been elevated into dry land, but that what is now deep 

 ocean has throughout all time been deep ocean. 



Temperature of Ocean Waters. Sea water continues 

 to contract as it cools until it is of about the freezing tem- 

 perature of fresh water. Hence cold water near the poles 

 gradually sinks and creeps under the warmer water of 

 lower latitudes, maintaining a temperature of 32 to 35 

 on the bottom, even at the equator. This steady creep of 

 cooled surface water along the bottom supplies the animals 



