Now let us pass from the record to that which it contains,--from the
book itself to the writing and the figures on its pages. This writing
and these figures consist of remains of animals and plants which, in
the great majority of cases, have lived and died in the very spot in
which we now find them, or at least in the immediate vicinity. You
must all of you be aware--and I referred to the fact in my last
lecture--that there are vast numbers of creatures living at the bottom
of the sea. These creatures, like all others, sooner or later die, and
their shells and hard parts lie at the bottom; and then the fine mud
which is being constantly brought down by rivers and the action of the
wear and tear of the sea, covers them over and protects them from any
further change or alteration; and, of course, as in process of time the
mud becomes hardened and solidified, the shells of these animals are
preserved and firmly imbedded in the limestone or sandstone which is
being thus formed. You may see in the galleries of the Museum up
stairs specimens of limestones in which such fossil remains of existing
animals are imbedded. There are some specimens in which turtles' eggs
have been imbedded in calcareous sand, and before the sun had hatched
the young turtles, they became covered over with calcareous mud, and
thus have been preserved and fossilized.

Not only does this process of imbedding and fossilization occur with
marine and other aquatic animals and plants, but it affects those land
animals and plants which are drifted away to sea, or 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