428 MR. G. W. LAMPLUGH ON THE 



YIII. Conclusion. 



To bring together my views as to the physical conditions pre- 

 vailing in this area during the formation of the drift deposits I 

 suppose that : — 



At a period not long anterior to that of the glaciation of the coast, 

 Flamborough Head was in existence as a bold promontory jutting 

 out into a sea whose level was slightly above that of to-day. 



Most of the mammals characteristic of the Glacial period were 

 already living, and tenanted the interior in large numbers. The 

 climate was moist and not very severe, the prevalent winds, as 

 shown by the sand-dunes of Sewerby, being from the west or 

 south-west. 



After the land had remained for a long time stationary, a slow 

 elevatory movement set in, and the climate became much colder ; 

 so that the Chalk-surface was disintegrated by frost and eroded by 

 sudden floods, which spread thick beds of muddy detritus over much 

 of the low or slightly sloping ground in the vicinity. Meanwhile 

 the bed of the North Sea was being rapidly filled with ice through 

 the great extension of the Scandinavian glaciers ; till at length the 

 Scotch and Scandinavian ice coalesced, and what remained of the 

 North Sea was well nigh ice-locked. The main current of this ice- 

 sheet followed the deepest part of the sea-bottom southwards, at 

 some distance from the coast but its flank, reinforced by ice flowing 

 down Teesdale and other valleys in the North of England, spread 

 westwards until it impinged upon the cliff's of Plamborough, and 

 upon the slopes of the Wolds and Moorlands. It eventually rose 

 higher than any portion of Flamborough Head, there attaining a 

 thickness of at least 500 feet close to its margin. Where the cliffs 

 were under 200 feet in height they were completely overridden by 

 this ice, but where higher they split the current, sending one 

 branch westwards for some distance into the Yale of Pickering, 

 and the other south-eastwards along the cliff'-line and finally 

 southwards into the Bay of Holderness. The drainage channels of 

 the streams flowing eastward were dammed by this ice, and lakes 

 were formed, wherein deposits of gravel and other material rapidly 

 accumulated. During this stage the Basement Clay was spread out. 



Then followed a period during which the edge of the ice remained 

 nearly stationary : and esker-like deposits of irregularly stratified 

 material were formed along it. Afterwards, the North-Sea ice 

 began to diminish, and its margin retreated for some distance, and 

 fluctuated considerably. At this time the Intermediate Stratified 

 Series and the Purple Clays were laid down. 



Then another great advance of the glacier took place, but with 

 ice chiefly from another source, the current being mainly composed 

 of Pennine ice, though this was still hemmed in and held up by the 

 North-Sea glacier. This ice overspread all the area occupied by 

 the previous flow, and even extended beyond these limits ; but the 

 flow was of shorter duration, and seems to have been suddenly 



