president's address* 33 



boulddr clay, obviously rearranged ; while other pits in the iinmediate 

 neighbourhood expose varieties and mixtures of one or the other 

 material. But, as true boulder clay occurs in the valley below, these 

 gravels must have been deposited, and that by rather strong currents, 

 on a hill-top — a thing which seems impossible under anything like the 

 existing conditions ; and, even if the lowland were buried beneath ice full 

 200 feet in thickness, which made the hill-top into the bed of a lake, it is 

 difficult to understand how the waters of that could be in rapid motion. 

 Eearranged boulder clays also occur on the slopes of valleys * which may 

 be explained, with perhaps some of the curious sections near Sudbury, 

 by the slipping of materials from a higher position. But at Old 

 Oswestry gravels with indications of ice action are found at the foot of 

 the hills almost 700 feet below those of Gloppa. 



Often the plateau gravels are followed at a lower level by terrace 

 gravels, 3 which descend towards the existing rivers, and suggest that 

 valleys have been sometimes deepened, sometimes only re-excavated. 

 The latter gravels are obviously deposited by rivers larger and stronger 

 than those which now wind their way seawards, but it is difficult to ex- 

 plain the former gravels by any fluviatile action, whether the water from 

 a melting ice-sheet ran over the land or into a lake, held up by some tem- 

 porary barrier. But the sorting action of currents in a slowly shallow- 

 ing sea would be quite competent to account for them, so they afford an 

 indirect support to the hypothesis of submergence. It is, however, 

 generally admitted that there have been oscillations both of level and of 

 climate since any boulder clay was deposited in the districts south of the 

 Humber and the Eibble. The passing of the Great Ice Age was not 

 sudden, and glaciers may have lingered in our mountain regions when 

 palaeolithic man hunted the mammoth in the valley of the Thames, or 

 frequented the caves of Devon and Mendip. But of these times of tran- 

 sition before written history became possible, and of sundry interesting 

 topics connected with the Ice Age itself — of its cause, date, and duration, 

 whether it was persistent or interrupted by warmer episodes, and, if so, 

 by what number, of how often it had already recurred in the history of 

 the earth — I must, for obvious reasons, refrain from speaking, and 



I content myself with having endeavoured to place before you the facts 

 of which, in my opinion, we must take account in reconstructing the 

 physical geography of Western Europe, and especially of our own 

 country, during the Age of Ice. 

 Not unnaturally you will expect a decision in favour of one or the 

 other litigant after this long summing-up. But I can only say that, in 

 regard to the British Isles, the difficulties in either hypothesis appear so 





1 For instance, at Stanningfield in the valley of the Lark. 

 _ 2 These contain the instruments worked by palaeolithic (Achoulean) man who, in 

 this country at any rate, is later than the chalkv boulder clay. 



1910. * D 



