become buried in
bogs or morasses; and the animals which have been trodden down by their
fellows and crushed in the mud at the river's bank, as the herd have
come to drink. In any of these cases, the organisms may be crushed or be
mutilated, before or after putrefaction, in such a manner that perhaps
only a part will be left in the form in which it reaches us. It is,
indeed, a most remarkable fact, that it is quite an exceptional case
to find a skeleton of any one of all the thousands of wild land animals
that we know are constantly being killed, or dying in the course of
nature: they are preyed on and devoured by other animals or die in
places where their bodies are not afterwards protected by mud. There are
other animals existing in the sea, the shells of which form exceedingly
large deposits. You are probably aware that before the attempt was made
to lay the Atlantic telegraphic cable, the Government employed vessels
in making a series of very careful observations and soundings of the
bottom of the Atlantic; and although, as we must all regret, up to the
present time that project has not succeeded, we have the satisfaction
of knowing that it yielded some most remarkable results to science.
The Atlantic Ocean had to be sounded right across, to depths of several
miles in some places, and the nature of its bottom was carefully
ascertained. Well, now, a space of about 1,000 miles wide from east to
west, and I do not exactly know how many from north to south, but at
any rate 600 or 700 miles, was carefully examined, and it was found that
over the whole of that immense area an excessively fine chalky mud is
being deposited; and this deposit is entirely made up of animals whose
hard parts are deposited in this part of the ocean, and are doubtless
gradually acquiring solidity and becoming metamorphosed into a chalky
limestone. Thus, you see, it is quite possible in this way to preserve
unmistakable records of animal and vegetable life. Whenever the
sea-bottom, by some of those undulations of the earth's crust that I
have referred to, becomes upheaved, and sections or borings are made,
or pits are dug, then we become able to examine the contents and
constituents of these ancient sea-bottoms, and find out what manner of
animals lived at that period.

Now it is a very important consideration in its bearing on the
completeness of the record, to inquire how far the remains contained
in these fossiliferous limestones are able to c