414 ME. G. W. LAMPLUGH ON THE 



AVe are compelled, then, to seek a marine horizon below the 

 Cromer Till, and there, I think, may possibly recognize an equiva- 

 lent in the " Leda-myalis bed " of the Geological Survey*. To this 

 correlation no objection can be raised on the score of levels or col- 

 ditious of accumulation, and with it the marine fauna of Speeton 

 and Sewerby, so far as it goes, agrees remarkably well ; while as 

 for the transported pebbles, such pebbles are, I believe, not absent 

 from any Norfolk marine gravel newer than the Red Crag, and occur 

 rather plentifully in beds as low as the Weybourn Crag. And as 

 these pebbles have probably been carried by floating ice drifting 

 southwards upon the j^orth Sea, the effect of the difference of nearly 

 a degree and a half in the latitude, and the position of Sewerby 

 under the lee of the prominent headland, may well account for their 

 greater abundance in that locality. 



Moreover, as will presently appear, there are very strong grounds 

 for believing that the Easement Clay represents the oldest actual 

 glaciation of the area. But the configuration of the district is such 

 that it could not be invaded by land-ice until long after the com- 

 mencement of glacial conditions ; and therefore, though the marine 

 beds of Sewerby and Speeton may not be strictly pre-Glacial, they 

 nevertheless, I think, contain the record of a period anterior to the 

 commencement of the glaciation of the east coast, and may be as old 

 as the Leda-myalis bed of Norfolk. 



It is not improbable that at the same period, in some other part 

 of the North-Sea basin, the shelly sands were being dejDosited which 

 were afterwards to be torn up and redeposited as part of the Base- 

 ment Clay aD Bridlington, Dimlington, and other places. 



2. The Chalky Hubble (5). — Passing now to the consideration of 

 the overlying drifts, we arrive first at the Chalk Rubble below the 

 Basement Clay. The connexion between this bed and the Basement 

 Clay is in some places so close as to indicate that their formation 

 must have been, to a certain extent, contemporaneous. Yet in other 

 sections, especially in the buried valleys, well-stratified sand or silt 

 intervenes between them, as though there had been a well-marhed 

 change of conditions after the deposition of the rubble (see PI. XIII. 

 figs. 5 and 7). The Danes' Dyke section yields important evidence 

 on this point, for there, as pointed out by Dakyns f? three different 

 seams of chalky gravel touch the Chalk slope in succession as the 

 lower beds die out (fig. 6), thus showing that the rubble may not 

 all have accumulated at the same period. But erratic boulders and 

 pebbles are occasionally present in the lowest bed, the true fine- 

 grained " chalky wash,'' even where overlain by stratified warp and 

 sand (Danes' Dyke and Pigeon Hole), and I am inclined to think 

 that this fine-grained rubble, though perhaps actually accumulated 

 on land by subaerial action, has yet been greatly modified and 

 partially re-arranged during the passage of the ice. From the 

 physical character of the district and its distance from high moun- 

 tains, there must, as above mentioned, have been a long interval 



* ' Pure Tallej Beds ' of S. V. Wood ; ' Westleton Beds' of Prestwich. 



t * Glacial Deposits north of Bridlington/ Proc. Yorks. Geol. & Polytechn. 

 See. Tol. vii. (18S0) p. 251. 



