47 



shelf as were available in the Atlantic, south of the ice shelf. It 

 is difficult in the present state of our knowledge, when conflicting- 

 views exist as to the level of the land, to pomt specifically to likely 

 areas. But it is probable that plaice and many other species 

 competed for the space at their disposal south of Ireland, and in 

 such a bay as the Channel may have presented. Rockall may have 

 suited some, the south of Iceland was also a possible region, and 

 the Greenland and American coasts must have been fully occupied, 



Post-Glacial Changes. — For the same reason it is just as 

 difficult to picture the North Sea when it emerged at the end of the 

 glacial period from the ice. The change of level which allowed 

 the Atlantic water finally to gain access to the Arctic Ocean, thereby 

 brmging about a warmer chmate and the retreat of the ice, probably 

 led at the same time to the extension of the North Sea bay. It 

 was very probably a shallow sea at this early period of its recent 

 history, possibly deepening on the Norwegian side, open to the 

 north, and extending as far south as say the 57th or 56th degree, 

 being still widely separated from the Channel by the land connexion 

 which existed at this period. The valleys of this region and the 

 North Sea bay would have been filled with glacier drift. Accordmg 

 to Pettersson, a fairly definite estimate of the time which has elapsed 

 since this took place may now be given. He refers to an unpub- 

 lished paper of de Geer who made a study of the peat bogs of Norway 

 and concluded therefrom that the beginning of the melting of the 

 ice in Norway occurred not more than 13,000 years ago.* This 

 must have succeeded the melting of the ice in the North Sea area, 

 a process which must have taken many years to accomplish. 



It is only necessary now to state for the purposes of this paper 

 that during the post-glacial period the North Sea Bay gradually 

 extended, and was finally put into communication with the Channel. 

 The gain of the sea was evidently for a period in excess of that 

 which is its present condition, for raised beaches point to a 

 submergence of some 100 feet in Scotland and Ireland, rather less 

 further south and east, and steps in the elevation which followed 

 have been traced at 50 and 25 feet. It was probably durmg the 

 submergence that the Straits of Dover were formed and Ireland 

 definitely cut off from Scotland. f 



* Der Atlantische Ozean walirend der Eiszeit. Intern. Rev. d. ges. Hydrob. u. Hydrog. 

 B. 6, 1913. 



t Nansen discussed the probable effects of such a submergence in Norwegian North Polar 

 Expedition, vol. III,, p. 420. 



