396 ME. G. "NV. LAMPLUGH ON THE 



wards this peculiarity becomes so marked that it is often difficult to 

 define the exact upward limit of the division, especially in places 

 where the lower layers of the upper Eoulder-clay are also stratified. 



The capping gravels (Sewerby Gravels) of these sections are sepa- 

 rable into two distinct and well-defined portions, the lower consist- 

 ing almost entirely of dark drift-pebbles, while the upper part, in 

 strong contrast, contains much white chalk. A similar arrange- 

 ment prevails in many of the gravel-beds farther east. 



The lower part of these gravels is often curiously interlocked 

 with the upper part of the Boulder-clay *, and the evidence points 

 to a simultaneous deposition of Boulder-clay and gravel. 



(f) Danes^ Dyhe (PI. XIII. fig. 5). — In this fashion, with continual 

 minor changes of detail, the beds may be traced to within 300 yards 

 of the Danes' Dyke ravine, where more striking variations occur. 

 Stratified chalky gravels with some sand are developed both above and 

 below the Basement Clay, and also, apparently, in the midst of the 

 upper Boulder-ciay ; and these gradually thicken at the expense of 

 the clays until at one place they usurp, for a short distance, the whole 

 of the section above the Chalk. Thin bands of Boulder-clay soon 

 reappear, however, and gradually thicken as they approach the 

 ravine. The coast-line here crosses a wide hollow in the Chalk 

 cut down to sea-level, which has been fiUed in with drifts, and 

 since partly re-excavated (see PI. XIII. fig. 5). The section at this 

 place shows complex alternations of Boulder- clay and gravels whose 

 arrangement will be best understood by reference to the figure f. 

 Of the bands of Boulder-clay the two lowermost (4\ 4^) die out 

 against the Chalk-slope. The space between them is held by rough 

 morainic gravel containing much chalk in large blocks, and seams 

 of cross-bedded sand (4 h) which also disappear. The higher of 

 these clays fades off in places into the overlying stratified deposits, 

 and it contains many shell-fragments, among the species present 

 being Saxicava norver/ica , Cardium groenlandkum, Nucida Cohboldicp, 

 Tellina halthica, &c. I have spent much time in exploring this 

 section [J, and consider that the beds up to this horizon represent the 

 Basement Clay, while the persistent upper band of brown Boulder- 

 clay (3) is all that remains of the upper Clay of Sewerby, this bed 

 and the underlying sand and gravel (3 b) together taking the place 

 of the Purple Clays of Bridlington and Holderness. 



Above this clay lie the Sewerby Gravels (2 b), the lower part 

 chalkless, and the upper layers composed chiefly of chalk-pebbles, 

 as noticed farther west. A few feet of loamy stuff overlies these 

 gravels at the cliff top (2 c), resembling a weathered Boulder- clay ; 

 and a little farther east (near Hartindale Gutter) a seam of Boulder- 

 clay certainly appears in these gravels, their contemporaneity with 



* See Dakyns, op. cit. (with fections illustrating this peculiarity). 



•f See also diagrams in J. Phillips's ' Geology of Yorkshire,' 3rd ed. pt. i. 

 ]3, 91 ; and J. E. Dakyns, ' Glacial Deposits north of Bridlington,' sujjra cit. 

 figs. 2, 3, 4, and 5. 



I To examine these drift-sections above the chalk-cliffs with safety it i& 

 necessary to fix a light rope at the top, to give secure band-hold. 



