president's address. 29 



observe that, though this view is the outcome of much acute observa- 

 tion and reasoning, 1 it is wholly dependent upon the ice-barriers 

 already mentioned, and that if they dissolve before the dry light of 

 sceptical criticism, the lakes will 'leave not a rack behind.' I must 

 also confess that to my eyes the so-called ' overflow channels ' much 

 more closely resemble the remnants of ancient valley-systems, formed 

 by only moderately rapid rivers, which have been isolated by the tres- 

 pass of younger and more energetic streams, and they suggest that the 

 main features of this picturesque upland were developed before rather 

 than after the beginning of the Glacial Epoch. I think that even ' Lake 

 Pickering,'- though it has become an accepted fact with several 

 geologists of high repute, can be more simply explained as a two- 

 branched 'valley of strike,' formed on the Kimmerid'ge clay, the 

 eastern arm of which was beheaded, even in preglacial times, by the 

 sea. 2 As to Lake Oxford, 3 I must confess myself still more sceptical. 

 Some changes no doubt have occurred in later glacial and postglacial 

 times; valleys have been here raised by deposit, there deepened some- 

 times by as much as 100 feet ; the courses of lowland rivers may 

 occasionally have been altered; but I doubt whether, since those times 

 began, either ice-sheet or lake has ever concealed the site of that 

 University city. 



The submergence hypothesis assumes that, at the beginning of the 

 Glacial Epoch, our islands stood rather above their present level, and 

 during that period gradually subsided, on the west to a greater extent 

 than on the east, till at last the movement was reversed, and they re- 

 turned 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 4 has described, can striate stones and even the 

 rock beneath it, and is able, on a subsiding 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 



1 P. F. Kendall, Quart. Journ. Geol. Soc, lviii. (1902), 471. 



2 See for instance the courses of the Medway and the Beult over the Weald clay 

 (C. Le Neve Foster and W. Topley, Quart. Journ. Geol. Soc, xxi. (1865), p. 443). 



3 F. W. Harmer, Quart. Journ. Geol. Soc, lxiii. (1907), p. 470. 



4 Quart. Journ. Geol. Soc, xxxiv. (1878), p. 556. 



