FOUNDATIONS OF THE GREAT DEEP 



buoy control, taut-wire control, and radio-acoustic ranging. 

 Their description will not be undertaken. 



Echo-soundings have shown that, while the older charts of 

 water depth need some corrections, yet these will not greatly 

 change figures for the average depths of the different oceans, 

 already and so expensively obtained by lead and line. See 

 Table I, which gives also mean heights for the continents. It is 

 seen that the mean depth of the ocean is five times the mean 

 height of the continents ; and that, in average, the land surface 

 stands nearly three miles above the bottom of the deep sea. 



Table I 



DIMENSIONS OF SEA, LAND, AND EARTH 



Among the greatest depths of water yet found are those at 

 the "deeps" of the western Pacific, with soundings as follows: 

 Nero Deep off Guam Island, at 5269 fathoms or 31,614 feet; 

 deep off Mindanao Island, at 5348 fathoms or 32,088 feet; and 

 deep off Japan, at 5441 fathoms or 32,646 feet. 



