76 THE HISTORY OF THE NORTH ATLANTIC 



been the perennial abodes of pelagic and abyssal creatures and 

 the refuge of multitudes of other marine animals and plants 

 in times of continental elevation. These general facts are full 

 of importance with reference to the question of the succession 

 of formations and of life in the geological history of the earth. 



So much space has been occupied with these general views, 

 that it would be impossible to trace the history of the Atlantic 

 in detail through the ages of the Palseozoic, Mesozoic, and 

 Tertiary. We may, however, shortly glance at the changes 

 of the three kinds of surface already referred to. The bed of 

 the ocean seems to have remained, on the whole, abyssal ; but 

 there were probably periods when those shallow reaches of the 

 Atlantic which stretch across its most northern portion, and 

 partly separate it from the Arctic basin, presented connecting 

 coasts or continuous chains of islands sufficient to permit 

 animals and plants to pass over. 1 At certain periods also there 

 were, not unlikely, groups of volcanic islands, like the Azores, 

 in the temperate or tropical Atlantic. More especially might 

 this be the case in that early time when it was more like the 

 present Pacific ; and the line of the great volcanic belt of the 

 Mediterranean, the mid-Atlantic banks, the Azores and the 

 West India Islands point to the possibility of such partial con- 

 nections. These were stepping stones, so to speak, over which 

 land organisms might cross, and some of these may be con- 

 nected with the fabulous or pre-historic Atlantis. 



In the Palaeozoic period, the distinctions already referred to. 

 into continental plateaus, mountain ridges, and ocean depths, 

 were first developed, and we find, already, great masses of sedi- 

 ment accumulating on the seaward sides of the old Laurentian 

 ridges, and internal deposits thinning away from these ridges 

 over the submerged continental areas, and presenting dissimilar 



1 It would seem, from Geikie's description of the Faroe Islands, that 

 they may be a remnant of such connecting land, dating from the Cretaceous 

 or Eocene period. 



