appeal for a reversal of the sentence to that higher court
of educated scientific opinion to which we are all amenable.

As your attorney-general for the time being, I thought I could not do
better than get up the case with a view of advising you. It is true that
the charges brought forward by the other side involve the consideration
of matters quite foreign to the pursuits with which I am ordinarily
occupied; but, in that respect, I am only in the position which is, nine
times out of ten, occupied by counsel, who nevertheless contrive to gain
their causes, mainly by force of mother-wit and common-sense, aided by
some training in other intellectual exercises.

Nerved by such precedents, I proceed to put my pleading before you.

And the first question with which I propose to deal is, What is it to
which Sir W. Thomson refers when he speaks of "geological speculation"
and "British popular geology"?

I find three, more or less contradictory, systems of geological thought,
each of which might fairly enough claim these appellations, standing side
by side in Britain. I shall call one of them CATASTROPHISM, another
UNIFORMITARIANISM, the third EVOLUTIONISM; and I shall try briefly to
sketch the characters of each, that you may say whether the
classification is, or is not, exhaustive.

By CATASTROPHISM, I mean any form of geological speculation which, in
order to account for the phenomena of geology, supposes the operation of
forces different in their nature, or immeasurably different in power,
from those which we at present see in action in the universe.

The Mosaic cosmogony is, in this sense, catastrophic, because it assumes
the operation of extra-natural power. The doctrine of violent upheavals,
_debacles_, and cataclysms in general, is catastrophic, so far as it
assumes that these were brought about by causes which have now no
parallel. There was a time when catastrophism might, pre-eminently, have
claimed the title of "British popular geology"; and assuredly it has yet
many adherents, and reckons among its supporters some of the most
honoured members of this Society.

By UNIFORMITARIANISM, I mean especially, the teaching of Hutton and of
Lyell.

That great though incomplete work, "The Theory of the Earth," seems to me
to be one of the most remarkable contributions to geology which is
recorded in the annals of the science. So far as the not-living world is
concerned, uniformitarianism lies there, not only in germ,