THE BASIN AND BED OF THE ATLANTIC. 315 



yet reached by the plummet in that ocean, the distance, in a 

 vertical line, is nine miles. 



582. An orographic view. — Conld the waters of the Atlantic bo 

 drawn ofif so as to expose to view this great sea-gash which 

 separates continents, and extends from the Arctic to the Antarctic, 

 it would present a scene the most rugged, gi^and, and imposing. 

 The very ribs of the solid earth, with the foundations of the sea, 

 would be brought to light, 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, in the 

 poet's eye, lie 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 iDhysical 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. — Plate XI. presents the latest attempt at such a 

 map. It relates exclusively to the bottom of that part of the 

 Atlantic Ocean which lies 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 

 lightest, Avhere it is not over twenty-four thousand feet deep. 

 The blank space south of Nova Scotia and the Grand Banks in- 

 cludes a district within which casts showing v«ry deep water 

 have been reported, but which subsequent investigation and dis- 

 cussion 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 ac- 

 curacy as the best geographers have been enabled to show, on a 

 map, the elevations above the sea-level of the interior either of 

 Africa or Australia. 



