LAMPLUGH: GLACIAL SECTIONS. 
247 
flat pebbles of chalk ; the rapid attenuation of the series southward, 
and its tendency to become finer in that direction, so that at Wils- 
thorpe only a few feet of finely-bedded warp-clay is seen ; the fact 
that an actual passage from sandy- gravel to sand can be seen in the 
cliff immediately south of the town (as shown in Part II., Fig-. 1, at 
C), taken in connection with the strong tendency of the Sewerbyand 
Bridlington Gravels to change into finer material as we leave the 
chalk, satisfies me on this point. 
And there is yet the additional evidence of the isolated outliers 
standing out here and there above the level of the freshwater marls 
and lower gravels, forming as it were, detached links of the once 
continuous chain. One such link is the oblong knoll of sandy gravel 
(marked Y on the ground-plan) near where the Gypsey Race passes 
under the railway ; another, the silty sand deposited on the crest of 
the Boulder Clay slope on which Belle Vue Terrace stands ; and 
others in the broken ridge of sand in Hilderthorpe. There is abun- 
dant proof that these beds have suffered severe erosion during the 
deposition of the later gravels ;* and from the character both of the 
Low-level gravel {2a), and the more recent stream-gravel (2) I 
should say that those are, more or less, re-arrangements of the 
older series. 
]V[y view of the origin of all these gravels is, that they are the 
product of fresh-water issuing chiefly from the Main Wold Valley, 
which debouches into the low ground of Holderness, close to the 
town of Bridlington, as may be seen by the contour lines on the 
ground -plan. 
Without entering into many details of the physical features of 
the district, which I shall presume to be known to those who will 
find matter to interest them in this paper, I may explain that this 
valle}" reaches right into the very heart of the Wolds, and, w-ith its 
branches and feeders, has a drainage area of about 86 square miles. f 
Its course upward from Bridlington to Rudstone, a distance of about 
6 miles, is nearly due west, but here the main valley swerves 
round to the north, pursuing that direction for 3 miles, as far as 
North Burton, where it again curves west, continuing on the whole 
* See last year's paper. f A rough estimate only. 
