278 LAMPLUGH : GLACIAL SECTIONS NEAR BRIDLINGTON. 
boss or ridge of Boulder-clay, wliich is bordered on the north and 
south by late-glacial or post-glacial gravels, as will be at once seen 
on referring to the coloured map attached to Part III. of this series. 
An examination of the same map will also show that this ridge of 
Boulder-clay is an almost direct prolongation on a lower level of the 
high chalk feature known as Bessingby Hill, which forms the south 
slope of the valley of the Gypsey Race, their continuity being broken 
only by a narrow spread of stream-gravel laid down by the Gypsey 
in comparatively recent times, and the Boulder-clay below it being as 
the drainage sections showed, close to the surface. When we remember 
the faithful manner in which Boulder-clays so frequently reproduce 
inequalities of the pre-glacial surface, these facts suggest that the 
ridge of clay in question, which is cut half across by the section we 
are discussing, is moulded upon a direct east and west prolongation 
of the chalk ridge, and that, w^ere the drifts removed, the chalk 
would be found much nearer the surface at this place than on either 
side, a probabiUty worthy the attention of well-borers. And if this be 
so, we may find therein additional proof, not indeed needed, that the 
Gypsey Valley (the ' Main Wold Valley ' of the interior) is cut lower 
than the present sea-level, and that a hidden portion of this valley 
probably exists between our section and tlie appearance of the chalk 
in the cliff at Sew^rby. 
The Basement Clay. 
History (incl Bibliography. — Before entering into details with 
respect to this clay, to which, as I have already stated, it is my 
intention to devote the chief portion of this paper, I think it will be 
profitable to consider the origin and use of this term as applied to 
our Yorkshire sections. Setting aside numerous prior references to 
' Upper ' and ' Lower ' Boulder-clays in Yorkshire, the term ' Basement 
Clay ' seems to have been first used by Messrs. Wood and Rome, wdio 
in 1868, in their paper " On the Glacial and Post-glacial Structure of 
Yorkshire and Lincolnshire " (Quart. Journ. Geol. Soc, xxiv., p. 147), 
describe under this name a lead-coloured clay abounding in chalk- 
debris and accompanied by stones and boulders from all sorts of rocks." 
Their figured section shows this clay at the cliff-foot from Kilnsea, near 
Spurn, to Dimlington, and again from Sand-le-mere, about four miles 
