The Past Condition of Organic Nature | Page 8

fine, if, instead of comparing immediately adjacent parts of two beds,
one of which lies upon another, we compare distant parts, it is quite
possible that the upper may be any number of years older than the
under, and the under any number of years younger than the upper.

Now you must not suppose that I put this before you for the purpose of
raising a paradoxical difficulty; the fact is, that the great mass of
deposits have taken place in sea-bottoms which are gradually sinking,
and have been formed under the very conditions I am here supposing.
Do not run away with the notion that this subverts the principle I laid
down at first. The error lies in extending a principle which is perfectly
applicable to deposits in the same vertical line to deposits which are not
in that relation to one another.
It is in consequence of circumstances of this kind, and of others that I
might mention to you, that our conclusions on and interpretations of the
record are really and strictly only valid so long as we confine ourselves
to one vertical section. I do not mean to tell you that there are no
qualifying circumstances, so that, even in very considerable areas, we
may safely speak of conformably superimposed beds being older or
younger than others at many different points. But we can never be quite
sure in coming to that conclusion, and especially we cannot he sure if
there is any break in their continuity, or any very great distance
between the points to be compared.
Well now, so much for the record itself,--so much for its
imperfections,--so much for the conditions to be observed in
interpreting it, and its chronological indications, the moment we pass
beyond the limits of a vertical linear section.
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 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