41 6 MR. G. W. LAMPLUGH ON THE 



it, the absence of conteraporaneous fauna from the associated 

 stratified beds (other than the transj)orted masses), the tumultuous 

 character of its arrangement, and, above all, its distribution with 

 regard to levels and to the shape of the ground show that, though 

 the exact mode of its deposition may remain uncertain, it can scarcely 

 be other than the direct product of land-ice. This ice seems to have 

 crept in upon the land from the north-east, coming u]) out of the 

 bed of the North Sea. 



The physical conditions of East Yorkshire throughout the Glacial 

 period seem to have been very favourable to the accumulation of 

 deposits, so that the work of the ice in this, its peripheral area, has 

 been to spread out successive sheets of material one over the other 

 in rude stratification wath very slight erosion of the underlying 

 surface. This was, no doubt, partly because of the general absence 

 of high elevations or steep confining boundaries and the presence of 

 a wide and open outlet to the southward, conditions which must 

 have attended every encroachment of the ice upon the district ; and 

 partly because the ice which reached this area was wasting rapidly, 

 and had little erosive power so near its margin. These conditions 

 must have affected every ice-flow in the region, and would have 

 brought about a similar copious deposit from any earlier glaciation 

 than that of the Basement Clay, bad such occurred. No real evidence 

 for the existeuce of such a deposit is, however, forthcoming, the 

 Basement Clay and its associated rubble forming the base of the 

 drifts wherever in our sections a base is seen. It may be objected 

 that there is in Holderness a considerable depth below the top of 

 the Basement Clay about which we know nothing ; but judging 

 from the behaviour of this clay in the coast-valleys between Scar- 

 borough and Saltburn, where it frequently swells out to a great 

 thickness (60 to 100 feet on the hollow ground), without much 

 change in the level of its upper surface, I think it is most probable 

 that this d'vision extends everywhere downward to the Chalk, or to 

 the gravels or pre-Glacial stratified beds which may rest on the 

 Chalk. This view is sustained by such records as we possess * of 

 the well-borings which have reached the Chalk in Holderness. 



The very fact that the area could not be invaded by land-ice until 

 the basin of the North Sea northward from Flamborough was quite 

 filled up by the glacier furnishes a further argument. If there had 

 been an earlier glaciation, then there must have been an accumulation 

 of the ice to this extent ; and this ice must afterwards have dis- 

 appeared and remained so long absent that there was time for the 

 Sewerby cliif-line to be carved out by the w^aters of an open sea. 

 Of such a double glaciation of the North-Sea basin there is neither 

 proof nor probability. 



Still further evidence for the non-existence of earlier Glacial beds 

 is furnished by the repeated occurrence of transported masses of 

 Secondary rocks in the Basement Clay. These have been derived 

 from various formations ; the White and Hed Chalk, Neocomian 

 Clay, Kimeridge Shale, Upper and Lower Lias Shale, are all repre- 

 *^ Geo!. Survey Mem. ' Holderness/ pp. 132-162. 



