PHYSICAL CONDITIONS— POSTGLACIAL. 527 



vanishes, and several other enigmatical appearances receive a 

 reasonable explanation. 



Whether any glacial deposits pertaining to this period can 

 now be identified in Norway and Sweden I cannot say, bnt it 

 seems not improbable that some of that unfossiliferous sand and 

 clay which cover the postglacial shell-beds over considerable 

 areas in the low grounds of those countries may be of the same 

 age as the older Carse-clays and late moraines and torrential 

 gravel and sand of the Scottish series. And perhaps evidence 

 will yet be forthcoming to show that a not inconsiderable 

 advance of the glaciers took place in Norway in postglacial 

 times. As yet, however, I am not aware that any trace of this 

 has been recognised. 



The climate during the formation of the 50-feet beach was 

 not only cold, it was also extremely humid. Extensive areas 

 which were formerly covered with forests were now dismantled 

 of trees, and converted into marshes and morasses. And this 

 change was not confined to maritime and mountain regions, but 

 characterised the inland low-lying districts as welL Neither was 

 it restricted to the area of the British Islands. Buried trees, as 

 we have seen, occur in the peat everywhere throughout Northern 

 Germany and adjacent regions. It was the very general distri- 

 bution of these trees in the peat-bogs throughout all North- 

 western Europe, which led me a number of years ago to infer 

 that their destruction and entombment had been due to changed 

 climatic conditions. And I am gratified to find that in this 

 opinion I have the support of the accomplished Norwegian 

 botanist, Axel Blytt, who from a study of the present distribu- 

 tion of the plants of Norway, and an examination of the peat- 

 bogs, has independently come to the conclusion that they afford 

 strong evidence of alternate dry or continental and wet or insular 

 climates, having prevailed throughout the Postglacial Period. 

 It cannot be denied that the mere separation of Britain from the 

 Continent, and the reappearance of the Irish Sea, the English 

 Channel, and the German Ocean, would of themselves produce 

 a deteriorating effect upon the vegetation, especially in what are 



