the mountains of North Britain coalesced with those of Scandinavia, and formed a vast mer de glace which spread like a fan far and wide, extending even into the Atlantic to within a short distance of the Færöe Isles. At the same time the Alpine glaciers, now reduced to pigmy dimensions, travelled far down their valleys. The Rhone glacier, for example, filled the whole of the basin now occupied by the Lake of Geneva to the height of some 3000 feet, and pushed its morainic debris high up on the slopes of the Jura Mountains. Similar phenomena obtained in corresponding latitudes in North America. The Glacial Epoch, or, as it is sometimes called, "the Great Ice Age," is by some regarded as going farther back than the Pleistocene period of Lyell, and the Quaternary of French writers. It lasted for a very long time, but not, according to some, as one continued span of advance and retreat of the ice, but rather as a series of successive Ice Ages, alternating with interglacial warm intervals. Professor James Geikie, who has made a special study of this subject, describes no less than six glacial epochs, with corresponding interglacial warm periods. On the other hand, Messrs Penck and Brückner limit their number to four. (Great Ice Age, 3rd ed., p. 607 et seq.)
That oscillations of considerable extent in the relative levels of sea and land had taken place during this period, is proved by the discovery of raised beaches and submerged old land surfaces in various parts throughout Western Europe. The former are well known to geologists, who describe them as existing at different elevations, sometimes amounting to over 1000 feet above present sea-level; and evidence of the latter, though more difficult to find, being under the sea, is not less convincing. On this point Professor Boyd Dawkins writes:—
