64 THE PROBLEMS OF THE DEEP SEA n 



111 this way, it would seem inevitable that the 

 surface waters of the northern and southern frigid 

 zones must, sooner or later, find their way to the 

 bottom of the rest of the ocean ; and there ac- 

 cumulate to a thickness dependent on the rate at 

 which they absorb heat from the crust of the earth 

 below, and from the surface water above. 



If this hypothesis be correct, it follows that, if 

 any part of the ocean in warm latitudes is shut 

 off from the influence of the cold polar underflow, 

 the temperature of its deeps should be less cold 

 than the temperature of corresponding depths in 

 the open sea. Now, in the Mediterranean, Nature 

 offers a remarkable experimental proof of just the 

 kind needed. It is a landlocked sea which runs 

 nearly east and west, between the twenty-ninth 

 and forty-fifth parallels of north latitude. Roughly 

 speaking, the average temperature of the air over 

 it is 75 Fahr. in July and 48 in January. 



This great expanse of water is divided by the 

 peninsula of Italy (including Sicily), continuous 

 with which is a submarine elevation carrying less 

 than 1,200 feet of water, which extends from 

 Sicily to Cape Bon in Africa, into two great pools 

 an eastern and a western. The eastern pool 

 rapidly deepens to more than 12,000 feet, and 

 sends off to the north its comparatively shallow 

 branches, the Adriatic and the ^Egean Seas. The 

 western pool is less deep, though it reaches some 

 10,000 feet. And, just as the western end of the 



