THE BASIN AND BED OF THE ATLANTIC. 303 



582. Could the waters of the Atlantic be drawn off so as to 

 An orographic view, cxposc to vicw tliis great sca-gash which separates 

 continents, and extends from the Arctic to the Antarctic, it would 

 present a scene the most rugged, grand, and imposing. The very 

 ribs of the solid earth, with the foundations of the sea, w^ould be 

 brought to hght, and we should have presented to us in one view, 

 in the empty cradle of the ocean, " a thousand fearful wrecks," 

 with that array of " dead men's skulls, great anchors, heaps of pearl 

 and inestimable stones," which, m the poet's eye, he scattered on 

 the bottom of the sea, making it hideous with sights of ugly death. 

 To measure the elevation of the mountain-top above the sea, and to 

 lay down upon our maps the elevated ranges of the earth, is 

 regarded in geography as an important thing, and rightly so. 

 Equally important is it, in bringing the physical geography of 

 the sea regularly within the domains of science, to present its 

 orology, by mapping out the bottom of the ocean so as to show 

 the depressions of the solid parts of the earth's crust there, below 

 the sea-level. 



583. Plate XI. presents the latest attempt at such a map. It 

 Plate XI. relates exclusively to the bottom of that part of the 



Atlantic Ocean which hes north of 10° south. It is stippled with 

 four shades : the darkest (that which is nearest the shore-line) 

 shows where the water is less than six thousand feet deep ; the 

 next, where it is less than twelve thousand feet deep ; the third, 

 where it is less than eighteen thousand ; and the fourth, or hght- 

 est, where it is not over twenty-four thousand feet deep. The 

 blank space south of Nova Scotia and the Grand Banks includes 

 a district within which casts showing very deep water have been 

 reported, but which subsequent investigation and discussion do not 

 appear to confirm. The deepest part of the North Atlantic is 

 probably somewhere between the Bermudas and the Grand Banks, 

 but how deep it may be yet remains for the cannon-ball and 

 sounding-twine to determine. The waters of the Gulf of Mexico 

 are held in a basin about a mile deep in the deepest part. The 

 BOTTOM OF THE ATLANTIC, or its depressions below the sea-level, 

 are given, perhaps, on this plate with as much accuracy as the 

 best geographers have been enabled to show, on a map, the eleva- 

 tions above the sea-level of the interior either of Africa or Austraha. 

 584. "What is to be the use of these deep-sea soundmgs ?" is 

 "What's the use " of a qucstiou that often occurs ; and it is as difficult 

 deep-sea soundings? ^q be auswcred in catcgorical terms as Frankhn's 



