But
there are circumstances which tend to show, that nothing like an inch of
chalk has accumulated during the life of a Crania; and, on any probable
estimate of the length of that life, the chalk period must have had a
much longer duration than that thus roughly assigned to it.
Thus, not only is it certain that the chalk is the mud of an ancient
sea-bottom; but it is no less certain, that the chalk sea existed
during an extremely long period, though we may not be prepared to give
a precise estimate of the length of that period in years. The relative
duration is clear, though the absolute duration may not be definable.
The attempt to affix any precise date to the period at which the chalk
sea began, or ended, its existence, is baffled by difficulties of
the same kind. But the relative age of the cretaceous epoch may be
determined with as great ease and certainty as the long duration of that
epoch.
You will have heard of the interesting discoveries recently made, in
various parts of Western Europe, of flint implements, obviously worked
into shape by human hands, under circumstances which show conclusively
that man is a very ancient denizen of these regions.
It has been proved that the old populations of Europe, whose existence
has been revealed to us in this way, consisted of savages, such as the
Esquimaux are now; that, in the country which is now France, they hunted
the reindeer, and were familiar with the ways of the mammoth and the
bison.
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