Western Ides of Scotland. 



99 



since assumed a level differing but little from one which it occupied 

 long before the oscillation took place. The further question as to 

 whether the postglacial raised beaches 1 of the British Isles are in the 

 same sense the result of temporary oscillations is not as readily solved. 

 It would be quite unsafe to generalize from the one case to the other ; 

 for the raised beaches and submerged forests have this essential 

 difference, that the latter are widely distributed phenomena, whereas 

 the former are distinctly grouped round a centre in the Scottish 

 Highlands. This centralization of the raised beaches indicates that 

 the oscillations they record have a different cause from that of the 

 submerged forests. This being the case, the tracing of the preglacial 

 shoreline into the area occupied by the postglacial beaches assumes 

 a double interest. 



Fig. 1. Diagram to show the distribution of the various beaches as at present 



known. 



Preglacial beach of the Western Isles of Scotland. 

 — Northern limit of preglacial beach of Southern Britain. 

 — • — • — 100-foot late glacial beach of Scotland. 

 p os t; glacial, Neolithic beach, so-called 25-foot raised beach. 



Up to the present, however, very little has been effected in this 

 direction. Some significance may attach to the fact that the preglacial 



1 For the benefit of readers who do not happen to be acquainted with the 

 subject it may be mentioned here that two distinct raised beaches are known in 

 Scotland, namely, the 100-foot late-glacial beach (with probably associated 

 shorelines at lower levels) and the 25-foot postglacial or Neolithic beach. Their 

 periods of formation were separated by one of elevation in which submerged 

 forests were found. 



