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