DRIFTS OF FLAMBOUOUGH HP^AI). 4(')) 



the Chalk, the «urt'aco remains plateau-like and regular, the drifts 

 levelling up the inequalities. This portion of the headland lies 

 definitely \\ ithin the chain of gravel-mounds, and when one stands 

 on these mounds and looks seaward it is remarkable how sharply 

 defined is the difference between this smooth space and the uneven 

 contours of the gravel-range bounding it. The same feature is 

 noticeable under similar circumstances near liempton. 



Until we reach North Sea Landing the drift consists chiefly of 

 Boulder-clay, sometimes in two, sometimes in three divisions, the 

 lowest usually containing many black flints and also many shell-frag- 

 ments. These flints are quite different in colour and shape from 

 those of the underlying Chalk. 



At North Sea Lauding the Chalk sinks to within a few feet of high 

 water, and the drifts thicken to nearly 100 feet, the lower portion con- 

 sisting very largely of well-stratified sandy and silty beds which rest 

 on thick chalk-rubble. As in other sections, these silts seem to pass 

 into, or form part of, the Basement Clay, but there is considerable 

 contortion and confusion, especially on the west side of the bay, 

 where thick chalkless gravels make their appearance in the lower 

 part of the drifts. The Upper Clay is continuous at the clifi'-top, 

 and is unaffected by the changes in the beds below. 



(p) The ThornxvicJcs. — Going westward, the Chalk rises to 70 or 

 SO feet in the flat-topped peninsula of High Holm, but sinks again 

 to near high- water mark in the two inlets known as Great and Little 

 Thornwick, where the buried valley-walls are broken through for the 

 last time. The sections here are analogous to that of North Sea 

 Landing, except that a very coarse morainic gravel without much 

 chalk comes between the chalk-rubble and the Basement Clay in 

 Little Thornwick. Stratified beds also again encroach upon the 

 Basement Clay, consisting, in this case, chiefly of clean sand and 

 tine gravel, with many shell-fragments. This gravel has yielded in 

 Little Thornwick a single battered, but nearly perfect, specimen of 

 Trophon antiquum^ var. contraiium ; but I do not regard it as of 

 marine origin. I have found in the Basement Clay itseK, just east 

 of North Sea Landing, a perfect specimen of Tellina bcdthica, with 

 valves united, and yet undoubtedly transported *. 



(q) Sanwick (PI. Xlll. fig. 10) f.— Beyond Little Thornwick the 

 old valley finally leaves the coast and the cliff-line becomes more 

 regular. The ground now rises steadily, so that in less than a mile 

 an elevation of over 300 feet is reached, the slope being most pro- 

 nounced at its commencement near Sanwick. Near this place the cliff 

 again reaches the skirt of the gravel-mounds and opens some partial 

 sections in them. One of these is shown in PI. XIII. fig. 10, wherein 

 an intermediate Boulder-clay (3 h'), presumably equivalent to the 

 Purple Clay of Holderness, is seen to be replaced by the gravels 

 with arched bedding (3 b) which form the heart of the mound. 

 Traces of remanie Speeton Clay again appear in the Basement Clay. 



Northward the gravel-mounds hang near the edge of the cliff as 



* For a similar example at Bridlingtou, see Geol. Mag. (1881) p. 540. 

 t The fishermen say ' Sanwick,' not ' Sarnwicks,' as on the Ordnance map. 



