To this genial stage succeeded an epoch of cold humid conditions, accompanied by geographical changes which resulted in the insulation of Britain and 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 widespread accumulations of growing peat. At this time glaciers reappeared in the glens of the Scottish Highlands, and here and there descended to the sea. The evidence for these is quite conspicuous, for the moraines are found resting on the surface of post-glacial beaches. Thus my friend Mr. L. Hinxman, of the Geological Survey, tells us 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 mile above the head of Loch Torridon.[BS] The evidence of this recrudescence of glacial conditions in post-glacial times is not confined to Scotland. I believe it will yet be recognised in many other mountain-regions; but already Prof. Penck has detected it in the valleys of the Pyrenees.[BT] Dr. Kerner von Marilaun has also described similar phenomena in the higher valleys of Tyrol, while Professor Brückner has obtained like evidence in the Salzach region.[BU] [BS] For Scottish post-glacial glaciers see J. Geikie: _Scottish Naturalist_, Jan., 1880; _Prehistoric Europe_, pp. 386,407; Penck: _Deutsche geographische Blätter_, Bd. vi., p. 323; _Verhand. d. Ges. f. Erdkunde, Berlin_, 1884, Heft 1; Hinxman: _Trans. Edin. Geol. Soc._, vol. vi., p. 249. [BT] "Die Eiszeit in den Pyrenäen": _Mitth. d. Vereins. f. Erdkunde_, Leipzig, 1883. [BU] Kerner: _Mitth. k. k. geograph. Ges. Wien_, 1890, p. 307; _Sitzungsb. d. kais. Akad. d. Wissensch. in Wien_, Bd. c., Abth. i., 1891; Brückner: _X. Jahresbericht d. geograph. Ges. v. Bern_, 1891. I have elsewhere traced the history of the succeeding stages of the post-glacial period, and brought forward evidence of similar but less strongly-marked climatic changes having followed upon those just referred to, and my conclusions, I may add, have been supported by the independent researches of Professor Blytt in Norway. But these later changes need not be considered here, and I shall leave them out of account in the discussion that follows. It is sufficient for my present purpose to confine attention to the well-proved conclusion that in early post-glacial times genial climatic conditions obtained, and that these were followed by cold and humid conditions, during the prevalence of which considerable local glaciers reappeared in certain mountain-valleys.[BV] [BV] For a full statement of the evidence see _Prehistoric Europe_, chaps. xvi., xvii.