1 98 The Scottish Naturalist. 



post-glacial. If space permitted, I should like to examine the 

 evidence, with a view to discover what were the geographical 

 conditions of north-western Europe at the period of this latest 

 immigration from the south. But I can do no more here than 

 briefly state the conclusions to which my studies have led me. 

 It seems most probable that the British area was little, if at all, 

 more extensive at the commencement of the period in question 

 than it is now, although it by-and-by became continental. ^ The 

 late glacial deposits of Scotland show that after the melting of 

 the last ice-sheet the sea gained upon the land to some trifling 

 extent, when certain of those beds of clay with arctic shells, which 

 are met with at low levels round our shores, were accumulated. 

 Immediately upon those latest glacial deposits comes the "buried 

 forest bed," and so-called "submarine peat;" and we seem to 

 pass at once from an insular condition with cold climate to a 

 continental condition with genial climate. The Pecte?i maxiimis 

 bed of the Firth of Clyde also occupies a clearly marked post- 

 glacial position, but it is almost certainly of older date than the 

 " forest-bed " and " submarine peat." This, of course, is only an 

 inference, for the two are never, so far as I know, found in juxta- 

 position. But as the deposits which immediately overlie the 

 "forest-bed" give us no indication of a milder climate than the 

 present, but on the contrary afford evidence, as will be presently 

 seen, of colder conditions, it seems to me that the Pecten maximus 

 bed can hardly belong to those later deposits, but is with most 

 probability to be relegated to a somewhat earlier date. I infer, 

 therefore, that after the cold of the last glacial period had 

 finally vanished, certain changes took place which resulted in a 

 great augmentation of the Gulf Stream, and that these changes 

 may have come about while the British Islands stood very much 

 at the same level as now. At this period the Scandinavian pen- 

 insula was submerged, at least in its southern parts, to the extent 

 of 300 feet or thereabout ; and the mussel-beds of Spitzbergen 

 prove a not much less amount of depression for that island. The 

 immense quantities of shell debris in the post-glacial beds of Spitz- 

 bergen and Scandinavia show that this period of partial submerg- 



^ There aVe good grounds for inferring, however, that after the close of the 

 glacial period— that is to say, after the youngest of the beds pertaining to that 

 period had been accumulated, and before any of our post-glacial deposits had 

 been laid down— the British Islands had some connection with the Continent. 

 But to discuss this point here would lead me away from the subject more 

 immediately under consideration. 



