422 MR. G. ^y. lamplugh on the 



de])osit, "with its innumerable subangnlar flints (mostly not of local 

 origin) and other boulders, the arched bedding, the absence of shells 

 from the silty seams, the eroded and scattered character of all the 

 specimens, and the curious mixture of forms, do not suggest ordi- 

 nary marine action. Moreover, in another pit on the same ridse 

 about one mile north-north-east of Kelsea Hill, I noticed recently 

 an irregular bed of stony clay one foot in thickness in the heart 

 of the shelly gravels *. 



On the opposite side of the Humber, eight miles farther west, at 

 Kirinington in Lincolnshire, there is indeed an undisturbed estuarine 

 deposit of muddy silt, with bivalves of three or four species and a 

 few other remains of an undoubtedly contemporaneous fauna, which 

 is usual!}" considered of the same age as the Holderncss gravels f. 

 But the evidence for the correlation is by no means convincing, and 

 it seems to me more than probable that the bed maybe a portion of 

 an older deposit, like those at Sewerby and Speetou, which has 

 escaped destruction. 



And, while admitting that on the Avhole there is stronger evidence 

 for the presence of the sea during the formation of the mounds 

 in Southern than in Northern Holderncss, 1 still find it difficult to 

 believe that de^^osits which are apparently conterminous, and have 

 so many features in common, should have had a widely different 

 origin. The solution may perhaps be, as suggested above, that the 

 sea was not entirely excluded from the old bay, and in some places 

 laved the edge of the glacier j. 



My conclusion, therefore, is that the Intermediate series of Flam- 

 borough Head aud of Northern Holderncss was formed at the edge 

 of the ice during a period of slow recession following a long pause ; 

 that, while these beds were being deposited at the margin, the forma- 

 tion of Boulder-clay was still going on over the area covered by the 

 glacier ; and that thus the Purple Clays of the Holderncss coast 

 were laid down contemporaneously with the stratified beds of the 

 interior and of Flamborough. 



There must have been during this period, as the late Prof. Carvill 

 Lewis pointed out, a great accumulation of fresh water in the vallevs 

 whose mouths were blocked by the North-Sea ice. Most of the 

 eastward-draining Yorkshire valleys would be in this condition, and 

 these bodies of water must have brought about the deposition of 

 large quantities of stratified debris, washed into them from the land 

 on one side and the ice on the other. Many of the gravels of 

 Flamborough Head, especially those on the lower southern side, 

 seem, as we have seen, to have been thus deposited. Farther north, 

 in the deep valleys of the Oolitic moorlands which lie open to the 



* Prof. Jas. Geikie observed Boulder-clay among the gravels at Kelsea Hill, 

 but had good reason for supposing it to be a tongue thrust out from the main 

 mass (' Great Ice Age,' 2nd ed. p. 378, figs. 59, 60). The above-mentioned 

 case, however, could not be thus explained, as the clay is 10 or 12 feet deep iu 

 gravel, and there is "no overlying Boulder -clay. 



t Geol. Survey Mem. ' Holderncss,' p. 58. 



+ Just as the sea re-sorts the moraiuic and freshwater gravels on the flanks 

 of tlie Muir and other glaciers in Alaska. 



