THE GLACIAL PERIOD AND THE EARTH-MOVEMENT HYPOTHESIS. 235 



fauna were eventually supplanted in our latitude by those 

 temperate forms which, as a group, still occupy this region. 

 The amelioration of the climate was accompanied by striking 

 geographical changes, the British Islands becoming united 

 with themselves and the opposite coasts of the continent. 

 The genial character of the climate at this time is shown by 

 the great development of forests, the remains of which occur 

 under our oldest peat-bogs. Not only did trees then grow 

 at greater altitudes in these regions than is at present the 

 case, but forests ranged much further north, and flourished 

 in lands where they cannot now exist. In Orkney and 

 Shetland, in the far north of Norway, and even in the Fseroe 

 Islands and in Iceland relics of this old forest-epoch are met 

 with. In connection with these facts reference may be made 

 to the evidence obtained from certain raised beaches on both 

 sides of the N. Atlantic, and from recent dredgings in the inter- 

 vening sea. The occurrence of isolated colonies of southern 

 molluscs in our northern seas, and the appearance in raised 

 beaches of many forms which are now confined to the waters 

 of more southern latitudes, seem to show that in early post- 

 glacial times the seas of these northern latitudes were warmer 

 than now. And it is quite certain that the southern forms 

 referred to are not the relics of any preglacial or interglacial 

 immigration. They could only have entered our northern 

 seas after the close of the glacial period, and their evidence 

 taken in connection with that furnished by the buried trees 

 of our peat-bogs, leads to the conclusion that a genial climate 

 supervened after the cold of the last glacial epoch and of 

 earliest postglacial times had passed away. 



To this genial stage succeeded an epoch of cold humid 

 conditions, accompanied by geographical changes which 

 resulted in the insulation of Britain aud Ireland — the sea 

 encroaching to some extent on what are now our maritime 

 regions. The climate was less favourable to the growth of 

 forests, which began to decay and to become buried under 

 wide-spread accumulations of growing peat. At this time 

 glaciers re-appeared in the glens of the Scottish Highlands, 

 and here and there descended to the sea, as in Arran, 

 Sutherland, and Ross. The evidence for these is quite con- 

 spicuous, for the moraines are found resting on the surface 

 of postglacial beaches. Thus my friend Mr. L. Hinxman, 

 of the Geological Survey, tells me that at the foot of Glen 

 Thraill well-formed moraines are seen in section reposing on 

 beach-deposits at the distance of about three-quarters of a 



