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