404 MR. G. W. LAMPLUGH ON THE 



far as Cat Nab, with the effect of causing the thickness of the drift 

 to oscillate between 60 or 80 feet and 10 or 15 feet. 



(r) Bempton (PI. XIII. fig. 11) and Baclcton (PI. XIII. fig. 12).— 

 ]3eyond the northern end of the great prehistoric rampart of Danes' 

 Dyke the mounds pass for a space inland (see Map, p. 387), hugging 

 the crest of the Bempton Valley, and the drifts dwindle to a band of 

 weathered Eoulder-clay, in one place not more than two feet thick, 

 resting on broken chalk or chalky gravel. In the overgrown state of 

 the sections in this vicinity it is difficult to decide the exact relation of 

 this clay, but there is every probability that it represents the Upper 

 Clay, and that the Easement Clay has tapered off into gravelly material 

 and crushed chalk. It must be borne in mind, as a point of great 

 importance in considering the origin of the beds, that the thinning 

 out of the deposits at this place is not directly dependent upon either 

 the elevation or the slope of the ground, since the drift lies thinnest 

 at Bempton, where the cliff is not more than 275 feet high, while 

 at Buckton and Speeton, farther west, where the Chalk rises to 

 between 850 and 400 feet, the Glacial beds have a thickness of 

 from 35 to 60 feet, and both Upper and Lower Boulder-clays are 

 certain!}' present. 



This thin covering of red Boulder-clay with a pebbly base continues 

 for over a mile. In one or two places, however, the drift thickens 

 to 30 or 40 feet in depressions of the Chalk, and is again divisible 

 into an Upper and a Lower bed (see PL XIII. Hg. 11). At Buck- 

 ton, where the gravel-mounds once more touch the coast, there are 

 one or two clear sections showing admirably the kame-like arrange- 

 ment of the Intermediate Series (see PI. XIII. fig. 12) and the 

 passage of earthy Boulder-clay through clayey gravel into clean- 

 washed stratified beds. This structure would, I believe, be found 

 in nearly every hillock if the section were cut in the proper direction 

 for displaying it. 



The highest point of the cliffs is reached at Kaincliff, in Speeton 

 parish, the altitude here being 440 feet*, of which over 50 feet is 

 drift, chiefly gravel. Even at this elevation I have found a few 

 fragments of marine shells {Tellina halthica, &c.) in the intermediate 

 gravels, in which a few black flints also occur. The stratified beds 

 frequently reach quite to the surface, as at Beacon Hill. The 

 drift-mounds slope steeply inland, and thin out so rapidly in that 

 direction that in some chalk-pits a little over half a mile from the 

 edge of the cliff, and fully 100 feet lower in level, two or three 

 feet of weathered Boulder-clay is all that remains of the Glacial 

 series. 



At Xanny Goat House, where one may descend, passing a small 

 crevice or cave, to the beach by a dangerous path, a curious breccia 

 coats the face of the vertical chalk-cliff for 70 feet or more below the 

 base of the driit. This is composed of drift-boulders and pebbles mixed 



* At Speeton Beacon, a mile farther west, the Chalk escarpment being here 

 half a mile inland, the six-inch Ordnance map records 454 feet ; but west of 

 this there is a considerable decrease in the altitude of the crest. 



