DEPTH OF THE OCEAN 27 



Deeps. — There is a special interest attached 

 to the greater depths of the ocean, so the 

 writer some years ago called all those areas 

 where the depth exceeds 3000 fathoms (18,000 

 feet) " deeps," and gave them distinctive 

 names, generally after exploring ships, navi- 

 gators and scientific men, thus following the 

 practice of naming mountain peaks. Fifty- 

 seven such " deeps," based upon some 500 

 soundings, are now known : 32 in the Pacific, 

 18 in the Atlantic, 5 in the Indian Ocean, and 

 2 in the Southern Ocean. Their positions are 

 shown in Plate II. They vary greatly in 

 outline : in some cases they are very irregular 

 or basin-like, but often they are trough or 

 trench-shaped and relatively close to continent- 

 al land. Some, like the Valdivia Deep in the 

 Southern Ocean and the Murray Deep in the 

 North Pacific, are believed to cover a large 

 area, while a few are very small, being based 

 on single isolated soundings. The total area 

 covered by these deeps is altogether only about 

 7 per cent, of the ocean-floor. Occasionally 

 a cone-like elevation with a depth on its 

 summit of less than 3000 fathoms rises from 

 the centre of a deep. 



Deepest Soundings. — Two deeps in the 

 Atlantic and seven in the Pacific have depths 

 exceeding 4000 fathoms, 46 soundings in 

 depths greater than 4000 fathoms having 



