G. F. WRIGHT — INTERGLACIAL SHELL-BEDS. 507 



eastern England arc confined to the area invaded by Scandinavian ice which moved 

 across the North sea bottom ; and between Flamboro head and Bridlington there 

 is very clear evidence that portions of the old sea-bottom were pushed up by the 

 ice to a height of nearly 300 feet. Such an instance was pointed out to me by Mr. 

 Lamplugh in the till overlying the chalk bluffs near Flamboro. Here it was clear 

 that a mass of clay, including shells, had been pushed along and drawn out by the 

 differential motion, and in some cases shells were found in the clay with the con- 

 cave side down, but tilled with sand, which had served to make it a compact mas- 

 capable of moving like any other pebble. These actual instances observed by Mr. 

 Lamplugh go very far to remove the antecedent objections which every one would 

 at first naturally urge to the theory. It should be noted also that the till at Mod 

 Tryfaen, at Macclesfield and at Ketley, as well as on the eastern coast of England, 

 contains numerous fragments of shells of the species found in the shell-beds. It is 

 easy to see. therefore, how they could be collected into thin beds by local currents 

 of water that must have arisen in connection with the melting of the glacial ice 

 which we know to have covered the locality where they were found. 



Secondly, the shells in most of these beds do not represent any definite fauna. 

 The forms associated represent those living in cold water side by side with those 

 living in warm water, and rock-haunting species with sand or mud loving species. 

 On the Isle of Man, Professor Kendall has found in the glacial drift of the north- 

 ern shore representatives of Nassa serrata, Brocchi, a mollusk which is now charac- 

 teristic of the Mediterranean sea and cannot endure even the present temperate 

 climate of the Irish channel. It certainly could not have endured the rigors of a 

 glacial climate, even with the supposed amelioration during the so-called inter- 

 glacial epoch. The species, however, lived in the Irish sea during the Pliocene 

 period. On the theory that the shells were pushed up from the bottom of the sea 

 by the advancing ice, this and all similar cases are readily accounted for. 



Thirdly, outside of the area in England which was not reached by glacial drift 

 there is a noteworthy absence of all the signs of submergence. "There are no true 

 sea beaches, no cliffs or sea-worn caves, no barnacle-encrusted rocks or rocks bored 

 by Pholas or Saxicava." Nor are any shells found in post-Tertiary deposits any- 

 where except in the area covered by ice which is known to have moved over a 

 sea-bottom. This is incredible if the subsidence supposed to have taken place really 

 occurred, since there must then have been numerous deep and quiet fjords specially 

 tit to harbor vast colonies of marine creatures, as such places are known to do at 

 the present day. In southern England the residuary soil upon the surface both of 

 the granite bosses of < lornwall and I (evon and over large areas of the chalk country 

 demonstrate the long-continued freedom of that area from subsidence. Nor are 

 1 here any positive evidences of subsidence of more than 200 or :;no feel in Scotland, 

 if even so much as t hat. 



There would seem to remain, therefore, no way of accounting lor the shell-bed 

 at Ketley except on the theory of Professor Lewis that they were pushed along 

 with other transported material by the Irish sea glacier. If one inquires further 

 into the more specific processes by which the underlying sand was deposited and 

 the overlying till spread over it, i1 is impossible to give more than a tentative ex- 

 planation. The recenl studies of the Alaskan glaciers by Professor \U'\<\, Mr. Gush- 

 ing and Mr. Russell show us how complicated are the deposits near the front of a 

 uieat glacier. The ice itself becomes covered with debris and forms harriers ami 

 furnishec at once hoih the margins of small lake- and streams and the water and 



