30 THE FAUNA OF THE DEEP SEA 



would vary constantly with the temperature of the 

 air above it. That is to say, it would be warmer at 

 the equator than in the temperate regions. The 

 temperature at the bottom would be the same as the 

 lowest temperature of the basin, that is, of the earth 

 that supports it. 



The great oceans however cannot be regarded as 

 simple basins of water such as this. The tempera- 

 ture of the surface water varies only approximately 

 with the latitude. It is generally speaking hottest 

 at the equator and coldest at the poles, but surface 

 currents in the intermediate regions produce many 

 irregularities in the surface temperature. 



Again, although we have no means of knowing 

 what the temperature of the earth is at 1,000 fathoms 

 below the surface of the ocean, it is very probable 

 that in the great oceans the temperature of the 

 deepest stratum of water is considerably lower than 

 the true earth temperature. This is due to currents of 

 cold water constantly flowing from the poles towards 

 the equator. If these polar currents were at any time 

 to cease, the temperature of the lowest strata of water 

 would rise. 



Although the polar currents cannot be actually 

 demonstrated nor their exact rapidity be accurately 



