234 lamplugh: larger boulders of flamborough head. 
along over the sea-bed. In numerous instances we have direct proof 
that pebbles have undergone marine erosion previous to their 
glaciation. 
It is of course possible that some of the undetermined sand- 
stones may have come from the Oolites, but this, as I showed in my 
first paper, is not probable when we consider the large number of 
recognizable carboniferous rocks, and compare it with the paucity of 
recognizable secondaries. 
This overwhelming preponderance of carboniferous and older 
rocks on Flamborough Head is more or less a local peculiarity due, 
as I believe, chiefly to the height and steepness of the unbroken line 
of cliffs on the northern face, which, existing in pre-glacial times, 
much as at present, deflected the lower layers of the ice-sheet, and 
allowed only the higher portion to pass over the cliff. This view- 
has been strongly impressed upon me by the detailed examination 
which I have recently made of the drifts of the whole headland, but 
it is beyond the scope of this present paper to discuss the matter 
further. 
With the object of proving among other things whether local 
differences in the distribution of the boulders could be detected by 
the means adopted, I selected a spot on the Holderness coast near 
Tunstall, between Hornsea and Withernsea, about thirty miles south 
of Flamborough, where erratics had accumulated in great numbers on 
the shore, and there, without specially particularizing them, I counted 
and examined 500 boulders wdiich lay within a given area, all over 
one foot in diameter, and obtained the following results : — 
4. BOULDERS AT TUNSTALL NEAR WITHERNSEA. 
Per centuiu. 
114 Limestones, undoubtedly Carboniferous ... 22 "8 
78 Sandstones and Grits, probably all, or nearly all 
Carboniferous ... ... ... 15*6 
78 Limestones, undoubtedly Jurassic, chiefly from 
the Middle and Lower Lias ... ... 15*6 
25 Septarian Clay-limestone nodules, probably all 
from Secondary clays, chiefly Kimeridge ... 5*0 
7 White Chalk 1*4 
