90 THE OCEAK 



waters of tropical regions, but extends some- 

 times a considerable distance outside the 

 tropics, as, for instance, in the north-east 

 Atlantic where it runs along the coast of 

 Norway. A bottom temperature between 

 50° and 60° F. occupies a narrow strip along 

 the shores of continents and around islands 

 within and near the tropical regions, and fills 

 the Mediterranean, while a bottom tempera- 

 ture exceeding 60° F. is almost wholly limited 

 to the tropics, filling up the Red Sea and occup- 

 ing the east end of the Mediterranean. The 

 bottom temperature may reach 70° F. in 

 depths beyond 100 fathoms around the groups 

 of coral islands in the Pacific, in the West 

 Indian seas, and in the Red Sea. 



General Remarks. — It has already been 

 stated that only 16 per cent, of the entire sea- 

 surface of the globe has a mean temperature 

 below 40° F., whereas of the entire sea-floor 

 92 per cent, is overlaid by water having a 

 temperature under 40° F. It has also been 

 stated that the warm surface waters of the 

 tropical regions form a comparatively thin 

 stratum, and therefore the great mass of ocean 

 water must be relatively cold. A rough 

 estimation of the proportion of the entire bulk 

 of water in the ocean having a temperature 

 below 40° F. gave over 80 per cent., so that 

 less than 20 per cent, has a temperature 



