Glacial History of Western Europe. 617 
several geologists of high repute, can be more simply explained as 
a two-branched ‘valley of strike’, formed on the Kimeridge Clay, the 
eastern arm of which was beheaded, even in pre-Glacial times, by the 
sea. As to Lake Oxford,! I must confess myself still more sceptical. 
The submergence hypothesis assumes that, at the beginning of the 
Glacial Epoch, our Islands stood rather above their present level, and 
during it gradually subsided, on the west to a greater extent than on 
the east, till at last the movement was reversed, and they returned 
nearly to their former position. During most of this time glaciers 
came down to the sea from the more mountainous islands, and in 
winter an ice-foot formed upon the shore. This, on becoming 
detached, carried away boulders, beach pebbles, and finer detritus. 
Great quantities of the last also were swept by swollen streams 
into the estuaries and spread over the sea-bed by coast currents, 
settling down especially in the quiet depths of submerged valleys. 
Shore-ice in Arctic regions, as Colonel H. W. Feilden? has described, 
can striate stones and even the rock beneath it, and is able, on a sub- 
siding area, gradually to push boulders up to a higher level. In fact, 
the state of the British region in those ages would not have been 
unlike that still existing near the coasts of the Barents and Kara 
Seas. Over the submerged region southward, and in some cases more 
or less eastward, currents would be prevalent; though changes of 
wind would often affect the drift of the floating ice-rafts. But 
though the submergence hypothesis is obviously free from the serious 
difficulties which have been indicated in discussing the other one, 
gives a simple explanation of the presence of marine organisms, and 
accords with what can be proved to have occurred in Norway, 
Waigatz Island, Novaia Zemlya, on the Lower St. Lawrence, in 
Grinnell Land, and elsewhere, it undoubtedly involves others. One 
of them—the absence of shore terraces, caves, or other sea marks—is 
perhaps hardly so grave as is often thought to be. 
But other difficulties are far more grave. The thickness of the 
Chalky Boulder-clay alone, as has been stated, not unfrequently exceeds 
100 feet, and, though often much less, may have been reduced by 
denudation. This is an enormous amount to have been transported 
and distributed by floating ice. The materials also are not much 
more easily accounted for by this than by the other hypothesis. 
A continuous supply of well-worn chalk pebbles might indeed be kept 
up from a gradually rising or sinking beach, but it is difficult to see 
how, until the land had subsided for at least 200 feet, the Chalky 
Boulder-clay could be deposited in some of the East Anglian valleys 
or on the Leicestershire hills. That depression, however, would 
seriously diminish the area of exposed chalk in Lincolnshire and 
Yorkshire, and the double of it would almost drown that rock. Again, 
the East Anglian Boulder-clay, as we have said, frequently abounds in 
fragments and finer detritus from the Kimeridge and Oxford Clays. 
1 F. W. Harmer, Q.J.G.S., vol. Ixii, p. 470, 1907. 
2 Q.J.G.8., vol. xxxiy, p. 556, 1878. 
