12 THE STORY OF LIFE IN THE SEAS. 



conductor of heat, and therefore the direct in- 

 fluence of the sun affects only the most superficial 

 layers. In the Equatorial region of the Pacific 

 Ocean, for example, the surface temperature is 

 sometimes as high as 80 Fahr., at 100 fathoms 

 from the surface it is only 60, at 400 fathoms 

 only 45, and at 1000 fathoms only a few degrees 

 above freezing point. On the land the tem- 

 perature falls as we pass from the coast to the 

 high plateaux and mountains, and we find snow- 

 capped mountains in Central Africa just as in 

 Switzerland or Norway. In the sea the tem- 

 perature falls as the thermometer is sent deeper 

 from the surface. Just as on the land the snow 

 line of the mountains is reached at high altitudes 

 in the Tropics, at lower altitudes in the Tem- 

 perate regions, and in the Arctic circle at the 

 level of the sea, so in the sea the cold water that 

 is found 500 fathoms below the surface in the 

 Tropics, reaches a higher level in the Temperate 

 regions, and is at the surface in the Arctic 

 circle. 



There is however one important point of dif- 

 ference between the distribution of these low 

 temperatures on the land and in the oceans, in 

 that they are broken in the former, and continuous 

 in the latter. If we were to imagine an aquatic 

 animal that could only live in temperatures 

 below 35 Fahr., it would be able to travel 

 below the surface from one pole to the other, or 

 from one ocean to another; but it would be 

 impossible for a terrestrial animal, exhibiting 

 the same peculiarity, to leave the Arctic circle 

 or the Alpine region without traversing lands 



