222 THE SEAS 



as on land, they are of great significance in the lives 

 of the animals living in the sea. For whereas most 

 land animals are warm-blooded and have special means 

 for keeping the temperatures of their bodies at a constant, 

 in the sea most animals are cold-blooded and must 

 take up the temperature of the surrounding water. 

 If our temperature rises only a few degrees the chemical 

 reactions are gone through at a dangerously increased 

 rate and give rise to fever. We can easily imagine 

 therefore that the passage of an animal into water five 

 or six degrees warmer than that in which it had been 

 living may have a profound effect upon it. It is probably 

 for this reason that the boundaries to the distribution of 

 many animals in the sea are those of temperature. (See 

 page 89.) 



Water requires a tremendous amount of heat energy 

 to raise its temperature ; the amount of heat necessary 

 to raise the temperature of a cubic foot of water by one 

 degree would raise by the same amount 3,000 cubic feet 

 of air. This is why in the summer the sea never has time 

 to reach the high temperature of the surrounding air 

 except sometimes just at the surface. 



For the same reason water is very slow to give up its 

 heat when once it is gained, and we notice that in winter 

 the sea is far warmer than the air, and acts as a reservoir 

 of heat. This explains why the climates of oceanic islands 

 and coastal lands are much more equable than those of 

 countries in the interior of great continents. The influence 

 of oceanic currents upon climate is well shown by a com- 

 parison of that of the British Isles, whose shores are bathed 

 by a branch of the Gulf Stream, with the climate of Labrador 

 which lies in the same latitude. 



At the same time any heat received at the sea surface is 

 imperceptibly slowly conducted away into deeper layers, 



