SHFPPARD : INTER-GLACIAL GRAVELS OF HOLDERNESS. 
11 
about eight feet thick and rests on the gravel, bifurcating towards 
the east, one tongue thinning out on the top of the gravel, and it 
may be that the tongue of red boulder clay in the sand previously 
mentioned, is part of the lower portion of this bed, although at 
present it is impossible to ascertain definitely. 
This red boulder clay is not nearly so compact as the purple 
boulder clay of the coast nor the basement clay of Bridlington and 
Dimlington, and the view has been put forward by some glacialists 
that it may be " the residuum left behind on the melting of a sheet of 
ice charged with clay and stones."* The fact that this clay is exposed 
more to the weather may, however, partly account for its being more 
friable than the under-lying boulder clays. On the other hand, the 
superior hardness of the other clays may perhaps be due to their 
having been subjected to a greater pressure of superincumbent ice 
during or since their formation. 
Mr. Lamplugh's explanation will account for the peculiar 
manner in which the clay flanks the gravel, and also explains 
how it is that this red boulder clay (the Hessle Clay of Wood and 
Rome) extends beyond the limit of the rest of the drift. f 
The various bouldersj found in the gravel seem to indicate that 
the Norweigan ice-sheet on coasting along our shores first passed the 
mouth of the Tees (the Teesdale Glacier having brought down Shap 
granite, Armboth dyke, Brockram, Carboniferous Limestone, &c.) ; 
then the Lias of Whitby (from which the Ammonites and Gryphse 
incurva were obtained), afterwards the Chalk at'Flambro', and then 
dragged with it the greater part of the beach of the pre-glacial Bay 
of Holderness, with its pholas-bored chalk-pebbles, bones, &c., and 
finally deposited the whole, mixed with the Scandinavian rocks and 
marine shells, together with the fresh-water Cyrena, so as to form the 
range of hills stretching from Flambro' to Paull and on into Lincoln- 
shire, this being its terminal moraine. 
* Lamplu^h, Drifts of Flambro' Head. Quart. .Journ. Geol. Soc, 
vol. xlvii., p. 424, (1891). 
t Ibid. Page 424. 
X Of course some of these boulders were probably scattered over a sea bottom 
before being picked up by the ice-sheet. See Quart. Journ. Geol. Soc, sup. 
cit., p. 410. 
