426 ME. G. W. LAMPLUGH ON THE 



and that no older division than the Purple Clay existed on Flam- 

 borough Head and the coast beyond. Now, however, that this 

 supposition has proved unfounded, and the Glacial deposits of the 

 whole coast-line are shown to be closely related, the comparison of 

 these drifts with those of other areas will have been greatly faci- 

 litated. Such comparisons between areas not actually conterminous 

 are always beset with difficulties ; but if it be allowed, as I think 

 it must, that the glaciation of East Yorkshire has throughout been 

 determined by ice extraneous to the district, it necessarily follows 

 that very wide areas must have been simultaneously affected. We 

 ought at any rate to be able to establish a correlation of all the 

 East-Coast drifts south, say, of the Scottish border; and even of 

 those on the low ground on the opposite side of England in the 

 same latitude, except in the immediate neighbourhood of moun- 

 tainous country, such as might be affected by the later local 

 glaciers. To attempt such a correlation, however, would require 

 a far longer study in the field of the details of other sections than 

 it has been in my power to make. It is with considerable diffi- 

 dence, therefore, that I put forward the following suggestions, which 

 must be taken at what they are worth. 



In the eastern parts of Northumberland and Durham, and 

 especially on the low ground bordering on the Tees, and south of 

 that river *, a similar tripartite division of the drifts has been 

 frequently observed, often with shell-valves and fragments of the 

 familiar species in the stratified beds ; and the difference between 

 the Upper and Lower Boulder-clays seems to be very much the 

 same as in East Yorkshire. 



Almost everywhere in East Lincolnshire from the Humber to 

 the Wash, two Boulder-clays, separated by sand and gravel con- 

 taining shell-fragments, are found between the Wolds and the 

 sea, though, as in Yorkshire, the Upper Clay is sometimes absent 

 where the gravels are piled up in mounds f. The Lower Clay 

 has generally been supposed to represent the Purple Clay of 

 Holderness, but I think there can be little doubt that the structure 

 of these areas, separated only by the Humber, is identical, and 

 that the Lower Clay of East Lincolnshire is the Basement Clay. 



In Norfolk, according to the later conclusions of S. Y. Wood j, 

 the Cromer Till should be considered the analogue of the Basement 

 Clay ; this seems to me most probable, the agreement between them 

 in several essential points being very close. The Contorted Drift 

 and " Middle Glacial " gravels together may represent the period 

 of the Purple Clays of Holderness and Intermediate beds of 

 Flamborough, and on this basis most of their characteristics may 

 be explained. The Chalky Boulder-clay may then be taken as 

 roughly equivalent to the Upper Boulder-clay of Yorkshire, though 



* Geol. Survey Mem. ' Northallerton and Thirsk,' p. 54 ; and Prof. G. A. 

 Lebour, ' Geology of Northumberland,' pp. 2 and 16, 1st ed. (1878). 



t A. J. Jukes-Browne, Quart. Journ. Geol. Soc. vol. xli. (1885) p. 114 ; Geol, 

 Survey Meras. ' East Lincolnshire,' p. 76, and ' Holderness,' pp. 56-63. 



I Quart. Journ. Geol. Soc. vol. xxxviii. (1882) p. 667. 



