sink a vertical pit through the
floor beneath us, and that I could succeed in making a section right
through in the direction of New Zealand, I should find in each of the
different beds through which I passed the remains of animals which I
should find in that stratum and not in the others. First, I should come
upon beds of gravel or drift containing the bones of large animals, such
as the elephant, rhinoceros, and cave tiger. Rather curious things to
fall across in Piccadilly! If I should dig lower still, I should come
upon a bed of what we call the London clay, and in this, as you will see
in our galleries upstairs, are found remains of strange cattle, remains
of turtles, palms, and large tropical fruits; with shell-fish such as
you see the like of now only in tropical regions. If I went below
that, I should come upon the chalk, and there I should find something
altogether different, the remains of ichthyosauri and pterodactyles, and
ammonites, and so forth.

I do not know what Mr. Godwin Austin would say comes next, but probably
rocks containing more ammonites, and more ichthyosauri and plesiosauri,
with a vast number of other things; and under that I should meet with
yet older rocks, containing numbers of strange shells and fishes; and in
thus passing from the surface to the lowest depths of the earth's crust,
the forms of animal life and vegetable life which I should meet with
in the successive beds would, looking at them broadly, be the more
different the further that I went down. Or, in other words, inasmuch
as we started with the clear principle, that in a series of
naturally-disposed mud beds the lowest are the oldest, we should come
to this result, that the further we go back in time the more difference
exists between the animal and vegetable life of an epoch and that which
now exists. That was the conclusion to which I wished to bring you at
the end of this Lecture.

End of The Past Condition of Organic Nature.

THE METHOD BY WHICH THE CAUSES OF THE PRESENT AND PAST CONDITIONS OF
ORGANIC NATURE ARE TO BE DISCOVERED.--THE ORIGINATION OF LIVING BEINGS.

In the two preceding lectures I have endeavoured to indicate to you the
extent of the subject-matter of the inquiry upon which we are engaged;
and now, having thus acquired some conception of the Past and Present
phenomena of Organic Nature, I must now turn to that which constitutes
the great problem which we have set before ourselves;--I mean, the