PRESIDENTIAL ADDRESS. 539 



The Interglacial Problem in the British Islands. 



Let us now consider the application of the Interglacial hypothesis to our own 

 land. 



The task of lollowing up the evolution of Prof. Qeikie's scheme through its 

 various phases, though instructive, is very confusing — one might even say 

 irritating — by reason of the continual changes of correlation which its author has 

 suggested in sorting out the British drift deposits into this orderly sequence. Our 

 East Coast boulder-clays, for example, were at one time held to cover four glacial 

 epochs, and their associated gravels to mark three mild interglacial epochs ; 

 and all except the first glaciation were supposed to be represented in the boulder- 

 clays of Lancashire and Cheshire.' Then, somewhat vaguely, it was allowed that 

 perhaps there were only three separate glaciations on the east coast, with a 

 minor episode of recession of the ice-margin ; and the Lancashire and Cheshire 

 boulder-clays were correlated with the two later of these glacial epochs.' But 

 subsequently we are reduced in the eastern district to two epochs of glaciation, 

 with one mild interval, of which the equivalents are all recognised also in the 

 north-west of England.^ 



While these and other similar changes may show a laudable desire of their 

 author to keep pace with the growth of definite information, I cannot help feeling 

 that they also show the premature character of the whole scheme, and a flexibility 

 in it that justifies suspicion. Moreover, in spite of these frequent changes in the 

 correlation and this local lopping off of glacial and interglacial episodes, we find, 

 with surprise, that the number of separate epochs in the classification has not 

 diminished, but has actually increased, by regrowth in fresh places. This, again, 

 may betoken the inherent vitality of the scheme, in which case it will gain 

 strength from every readjustment ; but it must certainly also denote the weakness 

 of its original basis. In considering its application to this country we will begin 

 by glancing at the evidence for the two earliest epochs of the classification. 



' Scanian ' {First Olacial) and ' Norfolkian ' (First Interglacial) Epochs, 



It is acknowledged that the First Glacial Epoch is not represented in Britain 

 by any boulder-clay or other evidence of land glaciation, but is based mainly upon 

 the supposed existence of a great Baltic glacier which overflowed the southern 

 part of the Scandinavian peninsula from south-east to north-west, a direction 

 difl'ering widely from that of the later ice-sheets. This glaciation of Scania is sup- 

 posed to have been contemporaneous with the deposition of the Cbillesford Clay 

 and Weybourn Crag of Norfolk, which contain a marine fauna indicative of cold 

 conditions. The Forest Bed series of Norfolk, with its temperate land fauna and 

 flora, is then interpreted as the product of a mild interglacial epoch (' Norfolkian ') 

 intercalated between the 'Scanian' glaciation and the more severe ' Saxonian ' 

 glaciation which followed ; and it is implied that during this mild stage the earlier 

 ice-sheet vanished. 



So far as I can gather, the recognition of the ' Scanian ' ice-sheet rests on 

 dubious grounds, being based chiefly on the disputed supposition that the lower 

 boulder-clay of North Germany is not the equivalent of the lower boulder-clay of 

 Sweden, but of a subsequent Swedish boulder-clay. For the ' Norfolkian ' dis- 

 appearance of the first Swedish ice-sheet no direct evidence is forthcoming, since 

 it is acknowledged that no interglacial deposits repre.^enting this stage have been 

 found in Sweden. But the Norfolk Forest Bed is here brought into tlae argument 

 to prove the ' deglaciation '^ — so that the Scandinavian geologist is invited to accept 

 the ' First Interglacial Epoch ' mainly on the supposed strength of the British 

 evidence, while the British geologist is expected to acknowledge the 'First Glacial 

 Epoch ' on the supposed strength of the Swedish evidence. This method of argu- 

 ment might have weight if the evidence afforded by either region were perfectly 

 definite. But in the present instance the conclusion that the Forest Bed repre- 



» Great Ice Age, 2nded.(1877), p. 393. ^ P«-*7««<onc£«rtf/;e(l881),pp.26.3-2GG. 

 • Great Ice A^e, 3rd od. (1894), chaps. ?xy. and x?vi., and Jovrn. Geol, 

 (suj>r0 cit.) 



