540 TRANSACTIONS OF SECTION C. 



sents an interglacial episode is not acceptable to tlie observers who have the fullest 

 knowledge of the Norfolk sections, Mr. Clement Reid pointing out that the enclos- 

 ing of the North Sea by the union of Britain with the southward continental land 

 affords an adequate explanation of the apparent climatal discrepancy between the 

 fauna of the sea and that of land ^ ; while Mr. F. W. Harmer shows the probability 

 of the transport of southern relics into this old estuarine deposit by river-drifting.' 



It has, indeed, been long recognised that the marine Pliocene deposits of eastern 

 England present us with an iutelligible chain of evidence for the gradual and un- 

 interrupted approach of the Glacial Period ; and to break this chain will require 

 stronger reasons than have yet been adduced. From the Coralline Crag, with seas 

 warmer than at present, to the Red Crag and Norwich Orag, with a northern 

 element steadily gaining ground in the fauna, we pass upward to the Chillesford 

 Clay and Weybourn Crag, wherein this element becomes predominant. Then 

 follows the period of slight elevation indicated by the Forest Bed, wherein, along 

 with its temperate-climate fauna, such northern forms as the musk ox and glutton 

 are associated ; and finally we gain just a glimpse of truly arctic conditions in the 

 Leda mi^alis bed and the Arctic freshwater bed, immediately before the advent of 

 the great ice-sheet that relentlessly blotted out both land and sea. 



* Saxonian ' {Second Glacial), 'Helvetian ' {Second Interglacial), and ' Polandian^ 



{Third Glacial) Epochs. 



Regarding the glacial severity of the ensuing stage — the ' Saxonian Epoch ' of 

 Professor Geikie's scheme — all are agreed ; and from this stage onward to the 

 close of the ' Glacial Period ' as usually understood, or to the close of the 

 * Polandian Epoch ' of the proposed classification, our difficulties of interpretation 

 arise not from lack of evidence, but rather from its superabundance and local 

 intricacies. 



It happens, fortunatelj', that the great bulk of our British drifts, with the 

 exception only of those in certain mountainous districts, are now included by 

 Professor Geikie within the two above-mentioned glacial epochs and the interven- 

 ing ' Helvetian Interglacial Epoch.' Therefore, in dealing more particularly with 

 the deposits assigned to these three epochs in certain typically glaciated districts, 

 we shall bring under consideration a considerable portion of the drifts of our 

 islands, and shall obtain results which can be applied to many other areas in 

 which the structure of the glacial deposits is essentially similar. The first district 

 to be considered shall be that which lies nearest us ; and in discussing the drifts 

 of East Yorkshire I propose to interweave some personal opinions that I have 

 deduced from the facts, which will afterwards be given wider application. 



East Yorkshire Drifts. — The long cliff'-sections between the Humber and 

 the Tees constitute one of the best exposures of lowland drifts in Britain, or even 

 in Europe. They fortunately include some deposits which reveal the conditions 

 prevailing in the neighbouring part of the North Sea basin just before the great 

 glaciation ; and they therefore enable us without interruption to continue the 

 history begun in East Anglia. 



The old cliff" of chalk and the marine beach at its foot which lie buried at 

 Sewerby, on the southern side of Flamborough Head, under sheets of boulder-clay 

 and gravel, prove to us that at the very beginning of glacial times the North Sea 

 still held possession of its basin, and with a surprisingly slight diflference from its 

 present level. A few far-transported stones in the old beach denote that ice-tioes 

 sometimes drifted southward into Holderness Bay ; while the bones of .animals 

 in the shingle, and in the blown sand which overlies it, prove that among the 

 denizens of the neighbouring land were the elephant {E. antiqmis), rhinoceros 

 (i?. leptorhinus), hippopotamus {H. nmphibius), and bison. This fauna is frequently 

 considered to be proof of mild conditions of climate ; but from the mode of its 

 occurrence in this and other places, I can find no reason to doubt that these 



> ' The Pliocene Deposits of Britain.' Mem. Oeol. Survey (1890), pp. 186-190. 

 • ' The Later Tertiary History of East Anglia.' Proo, Oeol, Assoc, vpl. xyii. (1902), 



