THE DEEP SEA AND ITS CONTENTS. 321 



shallow bottom which usually border the existing coast-lines are 

 to be regarded as submerged portions of the adjacent land- 

 platforms. The form of the depressed area which lodges the 

 water of the deep ocean is rather, indeed, to be likened to that of 

 a flat waiter or tea-tray, surrounded by an elevated and steeply 

 sloping rim, than to that of the basin with which it is commonly 

 compared. And it further becomes obvious that the real border 

 of any oceanic area may be very different from the ostensible border 

 formed by the existing coast-line. 



Of this difference between the shallow waters covering sub- 

 merged land, and the sea that fills the real ocean basins, we have 

 nowhere a more remarkable example than that which is presented 

 to us 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 eleva- 

 tion 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 con- 

 tinuity 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 Galway, 

 and that of the Western Hebrides to beyond St. Kilda ; but 

 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 ontside the 

 hundred-fathom line in the Bay of Biscay (a considerable 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 United States ship 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 



