onvey 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