THE DEEP SEA 



have now been taken. Among these is the famous 

 " Challenger deep " in the north-west Pacific, of 

 5,269 fathoms, nearly six miles, in which Mount 

 Everest would be more than engulfed. In fact, its 

 summit would be 2,600 feet below the surface. 

 Another instance is the " Swire deep," off Mindanao, 

 of 5,348 fathoms, over six miles, in which Mount 

 Everest might be submerged with 3,087 feet to spare. 



Pressure. Great depth means a great weight of 

 water ; it follows that there must be enormous 

 pressure in the Deep Sea. At 2,500 fathoms it is 

 2J tons on the square inch, perhaps twenty-five 

 times as much as the pressure in the cylinder 

 of an average railway locomotive. -Even the water 

 is compressed, and bodies into which the water 

 cannot penetrate quickly enough are squeezed 

 almost beyond recognition when they are sunk 

 to great depths. The Challenger explorers found 

 that a piece of wood sunk to the abysses was so 

 heavy when pulled up again that it sank in water. 

 The muscles of a dead animal, such as a whale, 

 must undergo a tremendous compression if the 

 carcass sinks. 



Temperature. The sun's heat is lost at about 150 

 fathoms, and the Deep Sea is therefore intensely 

 cold. With relatively little change (two or three 

 degrees in the course of the year) the temperature 

 remains near the freezing-point of fresh water (32 

 Fahr.). The bottom temperature may be below 

 30 Fahr. in Polar waters, and over the greater part 

 of the whole sea-floor an eternal winter reigns. 

 What a contrast this is to the changefulness of the 



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