150 » O. Fisher—On the Cromer Cliffs. 
implied by Mr. Reid, between the “ploughing” action of icebergs 
and the assumed “pushing” action of a great glacier or ice-sheet. 
I submit that many, at least, of the appearances in the Cromer cliffs 
are better explained by the thecry I suggested in my paper already 
referred to. I thought that the contortions, seen in the cliff, showed 
the intersection of its face with undulations radiating from centres, 
like those formed on still water when its surface is disturbed, rather 
than its intersection with parallel rolls like those shown in Mr. Reid’s 
diagram. My theory was thus expressed (op. cit. p.549): “If amass 
of material is spread out equably over another, both being in a plastic 
state, the surface of their junction will be horizontal. But if a quan- 
tity of one such material be dropped upon a limited space of the other, 
it will sink down into it, and the depth to which it sinks into it will 
depend upon the quantity which falls. The material of the lower stra- 
tum, which is squeezed aside by the intrusion, will be driven into folds 
all around the area invaded by the foreign mass. This will, I believe, 
explain many of the anomalies of what has been called the contorted 
drift. Wherever considerable contortions occur, they will be found to 
-be connected with the dropping of a mass of sand, gravel, or chalk, 
or of some matter differing from the stratified clay which is 
thrown into contortions by it. When the mass is very large, it some- 
times has sunk down through, not only the upper, but also, the 
lower part of the Lower Boulder-clay ” (1st Till); “and in one case 
I noticed that it had deranged the horizontality of the laminated ” 
(Preglacial) “beds beneath.” ‘This case is illustrated by the diagram 
already referred to as well as by those given below. Suppose a boat 
load of sand and gravel dropped upon the muddy bottom of a pond: 
that would be an illustration of what I mean. My supposition 
would explain the upper part of the drift being sometimes less con- 
torted than the lower (as marked by Mr. Reid), because nearly level 
sheets might be subsequently spread over sunken masses. 
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Fic, 3.—Aiguilles, derived from a mass of nearly vertical beds of shingle, denuded 
out of the face of the cliff of glacial sandy clay (‘‘ contorted drift’’) in which 
it was once enveloped; as seen from the beach beneath. Near Sherringham, 
May, 1864. 
With regard to the “Chalky Boulder-clay,” I confess that I 
supposed that the “Chalky Boulder-clay,” or third division of 
