100 THE OCEAN 



from great pressure increases, and by this 

 process some heat is taken up, which is drawn 

 from the Hquid, lowering its temperature. 

 When, therefore, a water- sample is drawn up 

 in an insulating water-bottle from a depth of, 

 say, 1000 fathoms, the temperature of the 

 sample is lowered, the amount of cooling 

 depending on the temperature of the water. 

 Thus a water-sample brought up from a depth of 

 550 fathoms in the cold Norwegian Sea is cooled 

 0-1° F. while being hauled up, but a sample 

 from the same depth in the warm Mediterranean 

 is cooled 0-3° F. 



A curious effect of the release of great 

 pressure in the depths of the ocean is some- 

 times seen in the case of fishes living in very 

 deep water. If for any reason they rise 

 much above the depth at which they are 

 adapted to live, the decrease of pressure causes 

 their swimming bladders to expand, and their 

 specific gravity is greatly reduced. Up to a 

 certain limit the muscles of their bodies can 

 counteract the tendency to float upwards, but 

 beyond that they are helpless, and go on 

 " tumbling upwards " to the surface, being 

 gradually killed by the distension of their 

 organs as the pressure is relieved. 



The effect of the great pressure in the ocean 

 on its inhabitants may be observed experi- 

 mentally by means of an ingenious apparatus 



