92 THE JOURNAL OF GEOLOGY. 



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 repre- 

 sented by the interglacial beds of north Germany, and by some of 

 the so-called postglacial alluvia of Bri*tain. 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 con- 

 tinental. The climate was temperate, but in the course of time became 

 more severe. This increasing severity seems to have been accompa- 

 nied by submergence, which amounted to something like loo 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. 



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 Nor- 

 way. 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 repre- 

 sent the work of the contemporaneous, but not confluent, ice sheet of 

 the continent. In the Alps, terminal moraines in the large longi- 

 tudinal 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 north- 

 western 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 



