File:The Quarterly journal of the Geological Society of London (13860133753).jpg

070
SEAELES V. WOOD ON THE NEWER
poured their waters into the wide
expanse of flat country aronnd
the Fen into which these other
four valleys opened. On the parts
vacated by the ice in its retreat
which were above the sea-level,
swamps and marsh-accumulations
formed, in which were preserved
the shells of freshwater Mollusca

and one of these, within the
Well and system, was disclosed in
the making of the cutting at
Casewick on the Great Northern
Railway (in the north centre
of sheet 64), and is described by
Prof. Morris in the ninth volume
of the Journal. It lies at an ele-
vation of about 110 feet above
0. D., and crowns the parting
which separates the vallej' of a riv-
ulet tributary of the Welland, from
that of a tributary of the Glen (a
small river which falls into the
Welland near the AVash), and is
overlain and overlapped by a sheet
of gravel which has been cut off by
denudation in the direction of either
valley. By permission of Prof.
Morris, and of the Council, I here
give that section (Cut i.).
When the ice of the Chalky Clay
was at its. greatest extension, and
the Pen country deeply buried
under it (see map of the Chalky
Clay accompanying first part of
this memoir, Q. J. G. S. vol. xxxvi.
pi. xxi. Map 1), the site of Case-
wick cutting was of course buried
under that ice, and the Oolitic
strata on which the fresh water bed
rests were undergoing degradation
by it

but as the ice retreated this
site was left as a low eminence of
bare rock, the drainage flowing
through the lower levels beneath
it. Upon this low eminence, just
out of the water, the freshwater
deposit, No. 3. of the woodcut,
was formed.
Although the ice was now re-
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