4. There followed a fourth period of glaciation, during which the major part of the Scottish Highland was covered by an ice sheet. Local ice sheets existed in the southern uplands of Scotland and in mountain districts in other parts of Britain, and the great valley glaciers sometimes coalesced on the low lands. Icebergs floated out at the mouths of some of the highland sea-lochs. In some places, terminal moraines were deposited upon marine beds which were then in process of formation. These beds are now 100 ft. above the sea level. At this time Scandinavia was covered by a great ice sheet, which yielded icebergs to the sea along the whole west coast of Norway. The ground moraines and terminal moraines of the mountain regions of Britain represent the deposits of this ice epoch. The upper diluvium of Scandinavia, Finland, and north Germany represent the work of the contemporaneous, but not confluent, ice sheet of the continent. In the Alps, terminal moraines in the large longitudinal valleys were made at the same time. This fourth glacial epoch was followed by a fourth interglacial interval, during which fresh water alluvial deposits were made, and also the "lower buried forest and peat" of Britain and northwestern Europe. At this time, Scotland seems to have stood 45 to 50 feet lower than now, and Carse clays and raised beaches represent the work of the sea. During this interglacial interval, Britain is believed to have become again continental, while the climate became so far ameliorated as to allow the growth of great forests. Subsequently the insulation of Britain was effected, and this was followed by a climate which was probably colder than the present. 5. The severity of the climate which marked the close of the fourth interglacial interval was such as to bring about local glaciation in some of the mountain valleys of Britain. Here and there the glaciers projected their moraines so far down the mountains that they rest on what is now the 45 to 50 feet beach. In the Alps, this fifth epoch of glaciation is represented by the so-called post-glacial moraines in the upper valleys. This is believed to have been the last appearance of glaciers in Britain. The dissolution of these glaciers was again followed by an emergence of the island, and by more genial climatic conditions.