The fourfold glaciation has been recognized with certainty only in Europe and North America, and even in these countries there is considerable doubt whether the northern ice-sheets shrank back as far as their present narrow limits during the interglacial periods. The long Mindel-Riss interglacial, which was probably the Chellean stage of flint industry,[3] was characterized by a very warmth-loving fauna, and it is possible, even probable, that during this period the glaciers melted completely away, except on the very highest summits. Of the climate of the Gunz-Mindel interglacial (termed by J. Geikie the “Norfolkian,” from the Cromer Forest Bed), we have comparatively little evidence. If the suggestion put forward in the following chapter is correct, the Gunz-Mindel interglacial was merely a local incident in the glaciation of the Alps, and not a true interglacial at all. Even the Cromer Forest Bed itself is not conclusive, since it is a river deposit largely composed of material drifted from lower latitudes. The Riss-Wurm interglacial (J. Geikie’s “Neudeckian”) nowhere gives us evidence of a climate as warm as the present, and as regards the Scandinavian and Canadian ice-sheets may have been merely an extensive and prolonged oscillation of the ice-edge. As regards the glaciation of Norway, the question has been investigated recently by H. W. son Ahlmann, who has published a long and detailed paper in English in volumes 1 and 2 of the Swedish _Geographiska Annalen_. He concludes that the morphology of Norway, without reference to stratigraphical or biological data, gives conclusive evidence of two glaciations. The first of these was the greater, and between that time and the second smaller glaciations there occurred an interglacial period of such considerable length that the greater part of the present gorges was then formed by fluvial erosion. We may, accordingly, consider the Ice Age as fourfold or double, according to the point of view from which we regard it. In the Alps and other mountain ranges on the borders of the great northern ice-sheets, which respond very readily to small changes, it was fourfold. In the peripheral regions of the northern ice-sheets themselves it has an appearance of being threefold or fourfold. In the more central regions of these great ice-sheets, where response to climatic change is very slow, there is no evidence of more than two glaciations; but in these regions, where the destructive effect of the ice reached its maximum, it is only by the merest chance that evidence of interglacial periods is preserved at all. And finally, in all other parts of the world we have evidence of only two glaciations at most.