400 
THE LAST DECADE. 
measures became exhausted the millstone grits were attacked ; their 
demidation was less rapid, but the results may be seen in the beds 
which form the middle lias ; and the increasingly calcareous rocks with 
which these beds terminated are attributed to the denudation of the 
Yoredale and Scar limestones. Most of these are now ironstones, 
and whence the iron was derived is not known, but there can be little 
doubt that the iron has taken the place of the calcareous matter 
which originally formed the beds. The large oysters occurring so 
abundantly in these beds indicate a shallowness of the water, and 
the consequent close proximity of the land. During the formation of 
the upper lias shales, the sea and land were again much depressed, 
and the coal measures were again broken up and redeposited to form 
the upper lias. The aggregation of the several beds constituting the 
oolitic rocks are considered in detail ; the cornbrash, the Kelloway 
rock, and the thick beds of Oxford clay are all traced to their origin 
in older rocks. The accumulation of great coral reefs which formed 
the coralline oolites were gradually depressed, so that the great thick- 
ness of Kimmeridge clay could be deposited above them. At the 
close of this period East Yorkshire ceased to be local, and became, 
during the deposition of the cretaceous rocks, part of a wide area ; 
and whilst in the south the gault and green sands were being accumu- 
lated, the more northern sea appears to have been deeper, and only a 
thin seam of red chalk represents the period. Above this the great 
thickness of the chalk was formed, and so ended the accumulation of 
the solid rocks which form the moors and wolds of East Yorkshire. 
The furthur action of atmospheric agencies on the surface is referred 
to, as well as the action of the glaciers which covered that part of 
the country during the glacial epoch. 
The Rev. E. Maule Cole, M.A., contributed a paper on the Red 
Chalk. He traced the occurrence of the red chalk at the base of the 
white chalk through a considerable area, the best sections probably 
occurring near Wharram and Burdale, a district visited by the Society 
a short time afterwards. The white chalk of Yorkshire somewhat 
resembles a basin in form, the rim of which has been raised to the high- 
est points by subterranean forces, and is nowthe thinnest portion, whilst 
in the centre of the basin the chalk has a thickness probably reaching 
