The Scottish Naturalist. 203 



the slopes, and accumulated huge cones de dejection at the foot of 

 the hills. These are nowhere better developed than in the valley 

 of the Earn, opposite the mountain tracks of such streams as the 

 Water of May and Dunning Burn. It is obvious that under such 

 physical conditions the flora and fauna of Scotland must have 

 been scanty in the extreme. What plants and animals may then 

 have existed here we cannot tell — the only organic relics of the 

 period which have come down to us being of marine origin. 



Snowfields and glaciers, however, eventually melted away, and 

 the sea at the same time retreated, so that eventually the British 

 area became united to the Continent. Now, you all know the 

 general history of the introduction of our present flora and fauna. 

 First came the arctic-alpine forms ; and these, as the climate im- 

 proved, were gradually succeeded by the present temperate species. 

 Step by step the arctic-alpine plants were driven northward or 

 compelled to retreat up the mountains, whither the Germanic 

 forms could not or would not follow. But this general statement 

 does not exhaust the matter ; the passage from late glacial times 

 to the present was by no means so simple as many suppose. It is 

 certainly not true that our climate has become continuously milder 

 since the close of the glacial period. There have been decided 

 oscillations of climate since the deposition of our 100 feet ter- 

 race, oscillations comparable to, but less pronounced than, those 

 which distinguished the Ice-age itself. As the evidence of such 

 post-glacial changes has not attracted the attention which it de- 

 serves, I may be allowed very briefly to indicate its general 

 character. 



One of the most remarkable of post-glacial accumulations is the 

 buried " forest-bed " of the Tay valley. It would be notable 

 enough even if it were an isolated phenomenon, but it is only a 

 sample of what may be seen at many different points on the 

 coasts of the British Islands and the adjoining shores of the 

 Continent. There can be little doubt that the buried trees of the 

 Tay and Earn, and those which occur in a similar position in the 

 post-glacial accumulations of the Forth valley, grew at a time 

 when a dense forest-growth covered all North-Western Europe 

 and wide regions which are now submerged. The relics of this 

 forest-growth are now met with not only in the so-called sunk 

 forests of maritime districts, but underneath the older peat-bogs 

 of our own and other countries. From the evidence of these tur- 



