2. There followed a second epoch of glaciation, when the ice sheet of Britain became confluent with that of the continent. This was the epoch during which the ice sheet reached its southernmost extension. Its depositions are found in the lower boulder clays of Britain, the lower diluvium of Scandinavia and north Germany (in part), the lower glacial deposits of south Germany and central Russia, the ground moraines and high level gravel terraces of Alpine lands, and the terminal moraines of the outer zone. During this second glacial epoch, Alpine glaciers are believed to have attained their greatest development. This epoch of extreme glaciation was followed by an interglacial interval, during which Britain is believed to have been joined to the continent. During this interval, the climate became temperate. In Russia (near Moscow) there seems to be evidence that it was milder and more humid than that of the same region at the present day. Toward the close of the mild epoch, submergence seems to have been accompanied by an increasing degree of cold, which finally ended in another glacial epoch. 3. The subsidence which marked the close of the second interglacial interval, marked likewise the inauguration of the third glacial epoch. Its work is represented in Britain by the upper boulder clay, in Scandinavia and Germany by the lower diluvium (in part), in central Russia by the upper glacial series, in Alpine lands by ground moraines and gravel terraces. The ice sheets of Scandinavia and Britain were again confluent, but did not extend quite so far south as during the second glacial epoch. This third glacial epoch is believed to have been followed by another interglacial interval, during which fresh water alluvia, lignite and peat accumulations were made. These are represented by the interglacial beds of north Germany, and by some of the so-called post-glacial alluvia of Britain. There were also marine deposits on the coasts of Britain and on the borders of the Baltic. During this interglacial interval, Britain is believed to have been continental. The climate was temperate, but in the course of time became more severe. This increasing severity seems to have been accompanied by submergence, which amounted to something like 100 ft. below the present sea-level on the coasts of Scotland. The Baltic provinces of Germany were also invaded by the waters of the North Sea.