OF NORFOLK AND SUFFOLK. 
131 
opinion of all competent authorities seems improbable, or the 
valley must have been filled to the brim with ice during 
their deposition. 
Gravels finer in character, generally regarded as of post- 
glacial, but certainly of later age than those of the plateaux, 
occur within the valleys at a lower level than the latter, and 
in places apparently above that which could have been reached 
by floods. These have been supposed to indicate successive 
stages in the erosion of the valleys by fluviatile action, but 
as the latter were clearly in existence in Chalky boulder-clay 
times, this hypothesis is now untenable. 
My own view of the conditions under which they originated 
is given below. 
SUMMARY AND GENERAL CONCLUSIONS. 
The facts here stated indicate that the first stage of the 
glaciation of Norfolk was accompanied by a direct invasion 
by the western portion of the great Scandinavian glacier 
which, filling the North Sea basin, overflowed also the plains 
of Northern Europe. Its moraine profonde, the Contorted 
Drift in an uncontorted, or but slightly contorted form, may 
be traced from the Cromer coast southward as far as Sotterley 
near Beccles, Withersdale near Harleston, Scole, and Bury 
St. Edmunds ; it may formerly have extended further to 
the south and probably overspread a portion of the Fenland. 
At a later stage the North Sea ice retreated from Norfolk 
and did not reappear, but it appears to have lain for a con- 
siderable period in proximity to the present coast-line, during 
which it heaped up as its terminal moraine a well marked 
ridge, that of the Contorted Drift of the Cromer cliffs. 
During the disappearance and melting of this ice-sheet the 
valleys of Central Norfolk were excavated, presumably by 
the action of torrential streams issuing from its gradually 
retreating margin. In other parts of the county, under 
the protection of the Cromer ridge, flat sandy heath-land 
originated, corresponding with the glacial “ sand plains ” of 
Denmark and Northern Europe. 
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