nimals which are
never found in fresh waters, being unable to live anywhere but in the
sea. Such are the corals; those corallines which are called Polyzoa;
those creatures which fabricate the lamp-shells, and are called
Brachiopoda; the pearly Nautilus, and all animals allied to it; and
all the forms of sea-urchins and star-fishes.

Not only are all these creatures confined to salt water at the present
day, but, so far as our records of the past go, the conditions of
their existence have been the same: hence, their occurrence in any
deposit is as strong evidence as can be obtained, that that deposit
was formed in the sea. Now the remains of animals of all the kinds
which have been enumerated occur in the chalk, in greater or less
abundance; while not one of those forms of shell-fish which are
characteristic of fresh water has yet been observed in it.

When we consider that the remains of more than three thousand distinct
species of aquatic animals have been discovered among the fossils of
the chalk, that the great majority of them are of such forms as are
now met with only in the sea, and that there is no reason to believe
that any one of them inhabited fresh water--the collateral evidence
that the chalk represents an ancient sea-bottom acquires as great
force as the proof derived from the nature of the chalk itself. I
think you will now allow that I did not overstate my case when I
asserted that we have as strong grounds for believing that all the
vast area of dry land at present occupied by the chalk was once at the
bottom of the sea, as we have for any matter of history whatever;
while there is no justification for any other belief.

[Illustration: CRETACEOUS NAUTILUS.]

No less certain is it that the time during which the countries we now
call southeast England, France, Germany, Poland, Russia, Egypt,
Arabia, Syria, were more or less completely covered by a deep sea,
was of considerable duration.

We have already seen that the chalk is, in places, more than a
thousand feet thick. I think you will agree with me that it must have
taken some time for the skeletons of the animalcules of a hundredth of
an inch in diameter to heap up such a mass as that. I have said that
throughout the thickness of the chalk the remains of other animals are
scattered. These remains are often in the most exquisite state of
preservation. The valves of the shell-fishes are commonly adherent;
the long spines of some of the sea-urchins,