The Past Condition of Organic Nature | Page 9

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 convey anything like an
accurate or complete account of the animals which were in existence at
the time of its formation. Upon that point we can form a very clear
judgment, and one in which there is no possible room for any mistake.
There are of course a great number of animals--such as jelly-fishes, and
other animals--without any hard parts, of which we cannot reasonably
expect to find any traces whatever: there is nothing of them to preserve.
Within a very short time, you will have noticed, after they are removed
from the water, they dry up to a mere nothing; certainly they are not of
a nature to leave any very visible traces of their existence on such
bodies as chalk or mud. Then again, look at land animals; it is, as I
have said, a very uncommon thing to find a land animal entire after
death. Insects and other carnivorous animals very speedily pull them to
pieces, putrefaction takes place, and so, out of the hundreds of
thousands that are known to die every year, it is the rarest thing in the
world to see one imbedded in such a way that its remains would be
preserved for a lengthened period. Not only is this the case, but even
when animal remains have been safely imbedded, certain natural agents
may wholly destroy and remove them.
Almost all the hard parts of animals--the bones and so on--are
composed chiefly of phosphate of lime and carbonate of lime. Some
years ago, I had to make an inquiry into the nature of some very curious
fossils sent to me from the North of Scotland. Fossils are usually hard
bony structures that have become imbedded in the way I have described,
and have gradually acquired the nature and solidity of the body with
which they are associated; but in this case I had a series of 'holes' in
some pieces of rock, and nothing else. Those holes, however, had a
certain definite shape about them, and when I got a skilful workman to
make castings of the interior of these holes, I found that they were the
impressions of the joints of a backbone and of the armour of a great
reptile, twelve or more feet long. This great beast had died and got

buried in the sand; the sand had gradually hardened over the bones, but
remained porous. Water had trickled through it, and that water being
probably charged with a superfluity of carbonic acid, had dissolved all
the phosphate and carbonate of lime, and the bones themselves had thus
decayed and entirely disappeared; but as the sandstone happened to
have consolidated by that time, the precise shape of the bones was
retained. If that sandstone had remained soft a little longer, we should
have known nothing whatsoever of the existence of the reptile whose
bones it had encased.
How certain it is that a vast number of animals which have existed at
one period on this earth have entirely perished, and left no trace
whatever of their forms, may be proved to you by other considerations.
There are large tracts of sandstone in various parts of the world, in
which nobody has yet found anything but footsteps. Not a bone of any
description, but an enormous number of traces of footsteps. There is no
question about them. There is a whole valley in Connecticut covered
with these footsteps, and not a single fragment of the animals which
made them has yet been found. Let me mention another case while
upon that