To do that rightly, and describe how the Fen came to be, one must go
back, it seems to me, to an age before all history; an age which
cannot be measured by years or centuries; an age shrouded in mystery,
and to be spoken of only in guesses. To assert anything positively
concerning that age, or ages, would be to show the rashness of
ignorance. 'I think that I believe,' 'I have good reason to
suspect,' 'I seem to see,' are the strongest forms of speech which
ought to be used over a matter so vast and as yet so little
elaborated.
'I seem to see,' then, an epoch after those strata were laid down
with which geology generally deals; after the Kimmeridge clay, Oxford
clay, and Gault clay, which form the impervious bedding of the fens,
with their intermediate beds of coral-rag and green sand, had been
deposited; after the chalk had been laid on the top of them, at the
bottom of some ancient ocean; after (and what a gulf of time is
implied in that last 'after!') the boulder-clay (coeval probably with
the 'till' of Scotland) had been spread out in the 'age of ice' on
top of all; after the whole had been upheaved out of the sea, and
stood about the same level as it stands now: but before the great
valley of the Cam had been scooped out, and the strata were still
continuous, some 200 feet above Cambridge and its colleges, from the
top of the Gog-magogs to the top of Madingley Rise.
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