irregularities of stratification to their lateral movement or 
downward pressure at the fall of the tide, when left stranded. 
The directions in which the pushing force must be supposed 
to have acted also agree with this theory. Though there 
is evidence of much oscillation in the level of the land at 
the period of the drift, the character of the shells found in 
it at Bridlington indicates a depth of not more than 100 
feet, and that dry land was near. This would lead to the 
inference that the chalk wolds were then above the sea, and, 
if so, there must have been a kind of bay at Bridlington, 
somewhat similar to the present. I have very carefully 
investigated the directions of the currents in this bay at the 
period of the drift, as shown by the ripple marks and other 
facts, and have been led to conclude that a tolerably strong 
current swept round its shores ; and that, in the centre, it 
was more tranquil and had a returning eddy. Comparing 
the directions of the currents with those of the contortions, 
I find, almost invariably, that the side on which the pushing 
force acted in the different parts of the ancient bay, agrees 
with that which would result from the drifting of an iceberg 
in the line of the current which prevailed there. 
Since, as I have above described, whenever the contortions 
are well displayed, they are seen to be underlaid and sur- 
mounted by undisturbed beds, the time when they were 
formed is absolutely fixed within narrow limits ; and, since 
they occur throughout the whole period of the drift, from 
the earliest to the most recent, it is clear that they cannot 
have been of contemporaneous formation. Hence we are 
compelled to suppose that the cause, whatever it might be, 
which produced them, acted during the deposition of every 
part. If, therefore, it is requisite to consider them to be due 
to the action of icebergs, we are led to the rather important 
theoretical conclusion, that they were present during the 
whole drift period, and not, as has been supposed by some 
highly distinguished geologists, merely at its close. 
