BRITISH POSTGLACIAL &> RECENT DEPOSITS. 401 



similar stages did exist may be reasonably inferred. The 100- 

 feet terrace must first have been eroded, and a wide, broad 

 trough scooped out of it, before the overlying Carse-clays could 

 have been laid down ; and it is unlikely that this erosion was the 

 work of the sea. The sea in which the Carse-clay was deposited 

 simply occupied an old land -valley, the bottom of which it 

 levelled up with silt and clay, while at the same time it cut 

 back the glacial deposits that formed its margin. Although no 

 ancient land -surface or forest -bed is known to occur at the 

 bottom of the Carse-clays, it is not unlikely that such a buried 

 forest does nevertheless exist. The character of the old valley 

 which lies concealed is very imperfectly known to us, for it is 

 only in a few places where its surface has been reached, and it 

 may quite well be that considerable remains of forest-vegetation 

 occupying the place of growth, may be buried under the great 

 Carse-lands of the Forth. We know, at all events, that a sub- 

 marine peat with tree-remains occurs at Largo, on the shores of 

 Fife, resting upon glacial deposits and evidently of older date 

 than the recent raised-beach of that neighbourhood. Be that, 

 however, as it may, the Carse- deposits of the Forth contain 

 frequent intercalated layers of tree -remains and sporadic logs 

 and snags, all of which point to the fact that an arboreal vege- 

 tation, similar to that which now covers the country, clothed the 

 hill-slopes and valley-bottoms at the time the Carse-clays began 

 to be laid down. A great change of climate must therefore 

 have supervened after the close of the Glacial Period and before 

 the Carse-clays were accumulated. Not only had the sea 

 retreated and the land acquired a larger area, but the arctic cold 

 had been succeeded by genial climatic conditions which induced 

 a luxuriant forest-vegetation. 



The shells of the Carse-beds are all of recent British species, 

 but the presence of the whale, which belongs to the large 

 Greenland species, may possibly indicate a somewhat colder 

 climate than the present. And this indication derives greater 

 force from the fact that the Carse-beds, when they are followed 

 up the valley, gradually merge with extensive river-deposits, 



2d 



