GENERAL INTRODUCTION 5 



upon this spot, when its loftiest peak would be fully covered 

 and lie over half a mile beneath the ocean surface (Plate 2). 



These deeps are not very numerous and cover only a 

 small proportion of the ocean floor. There are 57 in all, 

 32 of which are in the Pacific, 5 in the Indian Ocean, 19 

 in the Atlantic, and one lying partly in one and partly in the 

 other of the latter two oceans. Each deep has been given 

 a name, such as the " Murray Deep " and the " Valdivia 

 Deep," after well-known oceanographers and research 

 vessels. The deepest sounding in the Atlantic ocean is 

 5,227 fathoms, off Porto Rico. 



Taken as a whole the depth of the oceans is very greats 

 for more than half of the ocean floor lies between two and 

 three thousand fathoms, while well over three-quarters is 

 deeper than a thousand. One realizes how comparatively 

 trivial in extent is the shallow water that lies around our 

 coasts when it is known that the average depth of the oceans 

 aad their adjacent seas is over two and a quarter miles. 



Ancient Beliefs 

 The extent of the oceans was not known to the ancients 

 and their ideas of what lay beyond the small world they 

 knew were probably mostly surmise and myth handed down 

 from generation to generation. The Chaldeans imagined 

 that the earth, which floated upon the eternal waters, was 

 surrounded by a ditch in which a river perpetually flowed. 

 The Egyptians likewise conceived ever-flowing around their 

 world a river on the surface of which floated a boat carrying 

 the Sun. But neither of these civilizations can be said to 

 have been maritime, and it was the Phoenicians who were 

 the great navigators of ancient history. Their knowledge 

 of the extent of the sea must have been very considerable, 

 since they ventured often through the Pillars of Hercules, 

 visiting the coasts of Europe and the British Isles. From 



