1869. | SEARLES WOOD—BOULDER-CLAY. 105 
extruded by that sheet and carried away by floating ice from the 
ice-foot during summer and distributed over the south of England, 
there to intermingle with material brought from other parts of the 
ice-foot ; and it is just at the part where the section so encounters 
this foot, on the south-west side of the Lincolnshire Wold, that the 
chalky clay is in the condition of almost pure chalk and is quarried 
for lime. The middle representation then, after leaving the northern 
portion of the Lincolnshire Wold enveloped in ice, intersects the ice- 
foot again where the chalky, or basement, clay of Eastern Holder- 
ness (a) indicates that the Wold débris was also extruded. It then 
exhibits the Yorkshire Wold, over which the purple clay without 
chalk extends, as well as the great vale beneath the Wold where 
the same chalkless clay occurs, as entirely occupied by the ice, and 
the sea blocked out by it. 
The lowest representation of this triple section indicates what I 
conceive to have been the position when the purple clay without 
chalk, and with Shap boulders, were deposited. This representa- 
tion supposes a further depression of the land to have taken place, 
so as to bring it about 1500 feet below its present level, and that 
in consequence so much of the ice-sheet as had before enveloped 
the Wold, and filled the great vale below it, had been floated up 
and wasted away by the sea, so that only the higher elevations of 
the north and north-west of England, and the extreme summits of 
the eastern moorlands, remained enveloped in ice. This depression 
having also covered the lowest parts of the dividing ridge with sea 
and placed the Wolds many hundred feet under water, floating ice, 
carrying Shap boulders, was enabled to pass over the lowest parts of 
the dividing ridge ; and thus, coincidently with the termination of 
all supply of chalk by the retreat of the ice-sheet from the Wold, 
consequent upon its deep submergence, we have the formation of a 
clay destitute of that material and containing Shap-boulders, which 
was thrown down direct on the floor of old formations over the 
great vale that skirts the Wold-escarpment, and generally over the 
north of England previously occupied by the ice. 
This deposit of 1500 feet submergence is represented as extend- 
ing over the purple clay with some chalk, because we can prove its 
extension there by outliers still remaining: but how much further it 
may have spread in a southerly direction I would not venture to 
conjecture. It may have thinned out greatly in that direction— 
probably it did so—so that the commencement of the denudation 
wrought by the sea as the land rose removed it, and with it went 
the Shap boulders ; for it is a remarkable fact that, wherever any 
great area of denudation has occurred in the Boulder-clay, the 
various boulders of that formation have disappeared along with the 
clay itself. 
The immense volume of the chalk débris which has been shed 
out to form the chalky clay appears to me to necessitate the admis- 
sion that there was a long period in which the land and its enve- 
loping ice-sheet remained stationary, at about the limits indicated 
in the map and in the middle representation of the triple section. I 
