486 S. V. Wood,jun. — American and British Surf ace-Geology. 
clay was converted into land and denuded, and then subsequently 
depressed beneath the sea ; but this view was only offered by us 
as an hypotkesis alternative to tbat wkich we regarded, and which 
I still regard, as the true one, viz. a change in the source of the 
morainic material due to the recession of the ice from the chalk 
country, which the gradual diminution upwards in the overlying 
clay of the chalk debris, and its eventual disappearance in the 
uppermost portion, seemed to us to indicate. In many sub- 
sequent references that I have made to the purple clay of York- 
shire, I have invariably regarded it as one continuous deposit 
with the clialky clay of East Anglia, and with the chalky clay 
which, underlying the purple, forms the base of the Glacial forma- 
tion of Soutli-Eastern Holderness, and seems identical with that of 
East Anglia. So far from being a separate deposit, this purple clay 
with lessening chalk debris, forms, in my view, about the middle 
portion of that one unbroken formation, the Upper Glacial, tbe 
deposit of which took place mainly in the horizontal form, and of 
which the chalky clay of East Anglia, and that forming the base- 
menf clay of Soutk-East Holderness, constitutes the earliest and 
preceding part, and the chalkless clay of Holderness, into which 
the purple clay with chalk passes up, and the clay of the more 
nortkern counties, constitutes the succeeding parts. 
Reverting to the case of morainic clay resting upon stratified 
sands with marine skells, I would call attention to the evidences 
which are available to sliow what kind of eflect has actually resulted 
from the action of glacier-ice upon strata softer than rock when 
these formed the floor occupied by it. Thus in Norfolk we have 
evidence of glaciers having occupied the valleys which were cut out 
of the Lower Glacial and Crag beds down to the Chalk, and left 
their moraine upon that formation as they receded. 1 Where this 
has occurred, not only is the Chalk beneath the moraine matter 
altogether altered in character, having become a greasy marl, but the 
lines of flint which it contains are ruptured, and forced violently 
upwards, and crumpled together. This feature is most conspicuous 
nearest the surface where the grinding pressure of the glacier on its 
bed was most feit, and becomes less and less downwards until deep 
down (in some cases not until a depth of twenty feet in this solid, 
though altered, Chalk is reached) the lines of flint are found to 
regain their undisturbed state. A representation of this action of 
glacier-ice upon the Chalk at Litcham was given by me in 1866, 
in a paper in the Quart. Journ. of the Geol. Soc. ; 2 and in a 
subsequent part of the present paper also I shall have occasion to 
describe the action of an ice plougli on sands in the Yare Yalley, 
1 See paper by myself and Mr. Harmer on the later Tertiary Geology of East 
Anglia, in Quart. Journ. Geol. Soc. vol. xxxiii. p. 74. 
2 vol. xxiii. p. 84. Instead of this action on the Litcham chalk having (as re- 
presented in the paper quoted) taken place during the formation of the Contorted 
Drift, I should now refer it to the time when, after the elevation of part of the 
Upper Glacial into land, the inland-ice pressed on the west of Norfolk, as explained 
in the sequel of the present paper ; the bed b of the section in the paper quoted not 
being, apparently, the Contorted Drift. 
