272 Dr. William B. Carpenter [Jan. 23, 



portional scale*) show themselves — except in cases of local dis- 

 turbance — as undulations of scarcely perceptible gradient. 



Again, we now know that the borders of these vast depressed 

 areas are generally, if not uniformly, very abrupt ; the sudden descent 

 from a comparatively shallow bottom to a very deep one, which was 

 first noticed in the line of soundings taken with a view to the laying 

 of the Atlantic Telegraph cable, being not an exceptional but a 

 general fact. Taking this as the real border of the North Atlantic 

 Ocean, and looking to the smallness of the gradients presented by its 

 sea-bed (except in the volcanic area of the Azores) until we come 

 upon the like steep inclination at some distance from the American 

 coast-line, which obviously marks the true western border of the 

 oceanic area, we see that the term " basin " is a misleading one ; a 

 far truer representation of the Atlantic depression being a flat 

 " waiter " with elevated sides, having an upward bulge along the 

 median line of its bottom. On this view, the shallow band which 

 generally intervenes between the edge of a deep Oceanic depression 

 and the ostensible coast-line, is really to be regarded as a submerged 

 portion of the adjacent Continental platform. 



The contrast between the real and the ostensible borders of the 

 Ocean-basins is nowhere more remarkably exhibited than in the seas 

 which girdle the British Islands. These are all so shallow, that their 

 bed is undoubtedly to be regarded as a continuation of the European 

 Continental platform; an elevation of the north-western corner of 

 which, to the amount of only 100 fathoms, would reunite Great 

 Britain to Denmark, Holland, Belgium, and France, and would bring 

 it into continuity with Ireland, the Hebrides, and the Shetland and 

 Orkney Islands. Not only would the whole of the British Channel 

 be laid dry by such an elevation, but the whole of the North Sea also, 

 with the exception of a narrow deeper channel that lies outside the 

 fiords of Norway. Again, the coast-line of Ireland would be extended 

 seawards to about 100 miles west of Gal way, and that of the 

 Western Hebrides to beyond St. Kilda ; while a little further west, the 

 sea-bed shows the abrupt depression already spoken of as marking the 

 commencement of the real Atlantic area. A like rapid descent has 

 been traced outside the 100-fathom line in the Bay of Biscay (a con- 

 siderable part of which would be converted into dry land by an 

 elevation of that amount), and along the western coast of Spain and 

 Portugal, where, however, it takes place much nearer the existing 

 land-border. The soundings of the U.S.S. ' Tuscarora ' in the North 

 Pacific, have shown that a like condition exists along the western 

 coast of North America : a submerged portion of its Continental 

 platform, covered by comparatively shallow water, forming a belt of 

 variable breadth outside the existing coast-line ; and the sea-bed then 

 descending so rapidly as distinctly to mark the real border of the 



* The use of a vertical scale very many times as great as tlic horizontal, tends 

 to mask this important fact. 



