DRIFTS OF FLAMBOROtJGH HEAD. 397 



the uppermost part of the Boulder-clay, and consequently their 

 Glacial age, being thus fully established. 



I believe that the reason for the predominance of gravels in this 

 neighbourhood is that the waters of the Bcmpton valley have, as 

 already suggested (p. 388), sought this outlet under the lee of the 

 headland, when their original course eastward was blocked by the 

 ice, 



A noteworthy feature in this section is that the upper layers of 

 the Chalk on the western slope of the valley are thrown into remark- 

 able contortions, which fade out downwards (see PI, XIII. fig. 5). 

 More convincing instances of glacial folding will presently be de- 

 scribed, but these contortions seem also to have been accentuated, 

 if not actually initiated *, by ice-pressure ; though it is curious that 

 these disturbances should be found not only on the higher part of 

 the slope, where the Boulder-clay and coarse gravels are in direct 

 contact with the Chalk, but also in the valley-bottom, where there is 

 6 or 8 feet of fine chalky rubble (5), overlain by an almost equal 

 thickness of well-bedded and apparently undisturbed silt and sand 

 (5 a) between the lowest band of Boulder-clay and the Chalk. I 

 have, however, recently seen in the fine chalk-rubble a large boulder 

 of quartzite, 21 inches in diameter, proving the presence of ice, either 

 during or prior to the formation of this bed f- 



(g) Hartindale Gutter. — East of Danes' Dyke the section is less 

 complicated ; the gravel beds in the Basement Clay die out upon 

 the slope and the clay-bands unite, so that we find again only two 

 Boulder-clays with a stratified bed between them. The Chalk now 

 rises higher, its thickness in the cliff" ranging between 50 and 80 

 feet ; and as there is for some distance no corresponding rise in the 

 surface, the drifts lose what the Chalk gains. Landslips and thick 

 vegetation render the sections very obscure for over a quarter of a 

 mile, and in this space the Upper and Basement Clays seem some- 

 times to be merged into one mass. 



At Hartiudale Gutter, which carries the drainage of Plamborough, 

 there is a clear section, not only in the cliff, but also in the ravine 

 at right angles to it. Here it is seen how rapidly the drifts thin out 

 inland, and how many of the difficulties of the sections may be due 

 to this cause. In the face of the cliff only one Boulder-clay is seen, 

 presumably the Basement Clay, overlain by chalkless, and chalky, 

 gravels ; but a few yards up the ravine an upper band of Boulder- 

 clay appears between two of the gravel-beds, and seems to thicken 

 inland, the section somewhat resembling that on the east side of 

 High Stacks (PI. XIII. fig. 8). This upper Boulder-clay also makes 

 a fitful appearance in the gravels in the cliff, both east and west of the 

 Gutter. 



This section illustrates the difficulties which meet us in attempt- 

 ing a correlation of the clays and gravels of different localities, the 



* There are some indications of a fault in the Chalk close by, which may be 

 partly responsible for this disturbance of the beds. 



t It has been supposed that the rubble was formed as a rain wash of the Chalk, 

 Dakyns, op. cit. p. 248 ; see also p. 415 of this paper. 



