398 MR. G. W. LAMPLUGH ON THE 



connexion between the beds being so intimate that it is scarcely 

 l)Ossible to separate them. 



(h) Beacon Hill (PL XIII. fig. 0).— Beyond Hartindale Gutter 

 the cliff rises steadily, till in a quarter of a mile it has gained an 

 additional 50 feet or more of altitude, attaining a total height of 

 about 180 feet, afterwards sinking sharply towards the depression 

 of South Sea Landing. The conspicuous mound-like feature thus 

 formed, known as Beacon Hill, stands, as already mentioned, at the 

 southern end of the chain of kame-like hillocks. 



Its structure is admirably revealed in the cliff-section (see fig. 6) : 

 and the arrangement of the beds in it closely resembles that seen 

 in many of the Holderness mounds, to which its likeness is indeed 

 more striking than in the case of any of the mounds farther north *. 

 We find from the cliff-section that the surface-feature is not due 

 to any increase in the height of the Chalk, but that it is entirely 

 caused by the exaggerated development' of the stratified beds of the 

 drift. 



Above the Chalk there is Basement Clay (4), not much thicker 

 than usual, with occasional fragments of marine shells. In 

 its upper portion this clay exhibits, in places, signs of passage 

 into the overlying stratified beds, so that no sharp line can be 

 drawn between them. These stratified beds (3 6), which in the 

 lieart of the mound have a total thickness of over 80 feet, consist, 

 in the lower portion, of tough laminated clay and warp, passing 

 upwards into strongly cross-bedded and faulted sands with fine 

 gravel, while in the upper part of the hill the gravels predomi- 

 nate. A few small shell-fragments, of the same species as those 

 that occur in the Basement Clay, may be picked out of the gravel, 

 but the fine sand and warp contain no fossils whatever. In the 

 middle of the hill these stratified beds come quite to the surface, but 

 on either fiank they are overlapped by reddish Boulder-clay (3), 

 which rises higher on the eastern slope than on the western. 



This is essentially the structure of all these mounds, whether on 

 Elamborough Head or in Holderness, in spite of great variation of 

 detail — a lower dark Boulder-clay, an intermediate series of more 

 or less stratified material, and an upper brown or red Boulder-clay 

 often discontinuous over the crest. Often where a lenticular patch 

 of sand or gravel is revealed in the cliff between two Boulder-clays 

 without actually showing the mound-structure, close examination 

 will demonstrate that the section does indeed cross the margin of 

 a mound whose centre either lies inland or has been carried away 

 by the sea. 



In descending the eastern slope of Beacon Hill, the overlapping 

 Boulder-clay thickens so rapidly that in less than 200 yards it has 

 replaced or cut out the greater portion of the stratified beds, leaving 

 only a gravel band a few feet in thickness ; and before reaching 

 the little bay of South Sea Landing even this has disappeared, the 



* See also dijigrara in J. R. Dakyns's ' Glacial Deposits north of Bridlington,' 

 sitjpra cif. fig. 6 ; and Phillips, ' Geol. of Yorks.' 3rd ed. pt. i. p. 91. 



