, 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 phaenomena 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, but in
blossom and fruit.

If one asks how it is that Hutton was led to entertain views so far in
advance of those prevalent in his time, in some respects; while, in
others, they seem almost curiously limited, the answer appears to me to
be plain.

Hutton was in advance of the geological speculation of his time,
because, in the first place, he had amassed a vast store of knowledge of
the facts of geology, gathered by personal observation in travels of
considerable extent; and because, in the second place, he was thoroughly
trained in the physical and chemical science of his day, and thus
possessed, as much as any one in his time could possess it, the
knowledge which is requisite for the just interpretation of geological
phaenomena, and the habit of thought which fits a man for scientific
inquiry.

It is to this thorough scientific training, that I ascribe Hutton's
steady and persistent refusal to look to other causes than those now in
operation, for the explanation of geological phaenomena.

Thus he writes:--"I do not pretend, as he [M. de Luc] does in his
theory, to describe the beginning of things. I take things such as