798 REPORT—1890. 
Basaltic rocks of various kinds are usually very numerous. The far-travelled 
boulders of granite, gneiss, schist, &c., thongh never absent, are always in small 
proportion, generally under 5 per cent. It is, as might be expected, in the local 
Secondary rocks that the greatest differences occur ; these are all but absent from 
the Flambro’ Head list, while at Filey, only a few miles away, they comprise over 
50 per cent. 
A petrological examination of a selection of these boulders has been carried out 
by Mr. A. Harker, M.A., F.G.S.,' who finds that some of the igneous rocks are 
certainly—and others probably—from the south and west of Norway; while 
others have been derived from the northern and eastern parts of the English Lake 
District; from Teesdale; from the Cheviot Hills; and from the southern part of 
Scotland. 
In discussing the theoretical bearing of these results, it is shown that they are 
consistent with the views, elsewhere expressed, that land-ice has moved southward 
over the bed of the North Sea, and, in doing so, has deflected and carried southward 
the glaciers which were streaming eastward from the Tees and other northern 
valleys, pressing them against the high eastern coast-line of Yorkshire. 
A well-glaciated surface of Coralline Oolite recently discovered under the drift 
near Filey Brigg yields positive evidence as to the direction of the ice-movement, 
the grooves and scratches pointing N. 20° E. Also in several places on Flambro” 
Head the upper layers of the chalk are puckered up into sharp folds, which die out 
downwards, and these have evidently been caused by a force bearing from north to 
south across the surface. 
5. Hast Yorkshire during the Glacial Period. By G. W. Lamptuau, F.G.S. 
In this paper the author sums up his observations on the drift deposits of the 
Yorkshire coast. The marine beds of Sewerby and Speeton are placed at the 
base of the glacial series, and it is argued that the ‘ Basement Clay’ registers the 
history of the first general glaciation of the area, which was wholly extrinsic, and 
in no degree dependent upon local accumulation. 
The Basement Clay with its shelly inclusions (Bridlington Crag) is explained 
as the result of the encroachment upon the coast of land ice, which had gradually 
filled up the northern part of the bed of the North Sea. This ice carried forward 
portions of the sea-bed and became charged with marine débris. Off Flambro’ 
Head it seems to have reached a thickness of about 500 feet, and the slope of its 
upper surface rose higher eastward. It slightly overtopped the chalk escarp- 
ment at Speeton, and gravels washed from its flanks were lodged on the crest of 
the Wold there, but the mass of the ice was deflected along the face of the cliffs. 
The lower portion of the headland, near Flambro’ village, was, however, com- 
pletely overridden, and the ice passed across into Bridlington Bay. Holderness, 
at that time an open bay, was overwhelmed up to the slope of the Wolds, but the 
Wolds themselves remained bare. 
The next stage, that of the ‘ Purple Clays’ of Holderness, seems to have been 
marked by a general lowering of the surface of the ice and by wide oscillations of 
its margin, so that a large portion of Holderness was uncovered, as was also the 
ground at the foot of the Wolds and Moorlands. These areas received thick but 
irregular deposits of silt, sand, and gravel (often with a thin sprinkling of marine 
shell-fragments), derived partly from the surface drainage of the ice and partly from 
the bare land to the westward. Within the margin of the ice, however, the for- 
mation of boulder clay was still going on, and thus it is that much of the ‘ Purple 
Clay’ of eastern Holderness is probably contemporaneous with the intermediate 
gravels of the interior and of the country north of Flambro’ Heal. 
Then followed the period of the Upper Boulder Clay. This clay, which is 
inclusive of the ‘Hessle Clay’ of Messrs. Wood and Rome, is best studied — 
north of the Wolds. Its source does not seem to have been quite the same as 
that of the Basement clay, the ice by which it was laid down coming chiefly 
from the high Carboniferous region in the north-west. If the glacier of the North — 
1 Printed in extenso in Proc. Yorks. Geol. and Polytech. Soc. for 1889 and 1890. 
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