Geological Society of London. 623 



gravels are widely spread, and show signs of sudden and tumultuous 

 action. Between the upland and lowland gravels he considered that 

 great denudation had taken place. He maintained that the boulders 

 and the materials of the gravels had been distributed by floating ice, 

 and that their presence on the summit of Dartmoor indicated that the 

 water on which the ice floated must have extended up to 1200 feet 

 above the present sea-level ; but he argued that this water was not 

 that of the sea, because no old sea-beaches or remains of marine 

 organisms are to be found in the region, although fresh- water shells 

 are preserved. He ascribed these phenomena to the presence of a 

 great freshwater lake, produced by the drainage of Europe being 

 dammed back by a great glacier flowing from the north-west (Green- 

 land) down the present bed of the Atlantic, and over the northern 

 parts of the continent. The author discussed the characters of the 

 superficial deposits in the southern and south-eastern counties, and 

 indicated the points in which these seemed to bear out his hypothesis. 

 The sequence of phenomena assumed by the author is as follows : 

 — Accepting Mr. Tylor's notion that the actual sea-level must have 

 been lowered during the Glacial period in consequence of the great 

 accumulation of water in the form of ice at the poles, he seeks a 

 point of departure for the Glacial period in the first evidence of such 

 a lowering of the sea-level. The Weybourne sands and the marine 

 beds of Portland Bill were deposited when the sea was at about its 

 present level, and the Bridlington Crag probably belongs to the same 

 period. The fossils found in these deposits show that the waters 

 were cold. The first stage of the Glacial period is that of the older 

 Forest-beds, and the immigration of a number of great Mammalia 

 and of Palaeolithic man indicates that the sea had retired from the 

 British Channel and the German Ocean, leaving these islands con- 

 nected with the continent. A great river probably ran southwards 

 through the region now submerged. The second stage is marked by 

 the continued advance of the ice from the north, the retreat of the 

 southern fauna and Palaeolithic man, and the arrival of Arctic 

 Mammals. The third stage saw the culmination of the Glacial 

 period and the greatest extent of the Atlantic glacier, which reached 

 to the coast of Europe, blocked up the English Channel, and caused 

 the formation of an immense lake of freshwater by damming back 

 the drainage of the whole of north-western Europe, as already indi- 

 cated. In the fourth stage the Atlantic glacier began to retreat, 

 and the sudden breaking away of the barrier of ice that blocked up 

 the mouth of the Channel caused the tumultuous discharge of the 

 waters of the great lake, by which the spreading of the lowland 

 gravels was effected. To this cause the author attributes the for- 

 mation of the Middle Glacial sands and gravels of Norfolk and 

 Suffolk. During the fifth stage the ice of the German Ocean con- 

 tinued to retreat ; but there was a temporary advance of the Atlantic 

 glacier, which again blocked up the Channel, and produced a second 

 great lake, which, however, did not attain so great a height as the 

 first, and its waters were not discharged in the same tumultuous 

 fashion. At this period the Upper Boulder-clay of Norfolk and 



