of Argyll has carried his studies of geological
philosophy so far as this point. For he defines uniformitarianism to
be the assumption of the "extreme slowness and perfect continuity of
all geological changes."

What "perfect continuity" may mean in this definition, I am by no
means sure; but I can only imagine that it signifies the absence of
any break in the course of natural order during the millions of years,
the lapse of which is recorded by geological phenomena.

Is the Duke of Argyll prepared to say that any geologist of authority,
at the present day, believes that there is the slightest evidence of
the occurrence of supernatural intervention, during the long ages of
which the monuments are preserved to us in the crust of the earth? And
if he is not, in what sense has this part of the uniformitarian
doctrine, as he defines it, lowered its pretensions to represent
scientific truth?

As to the "extreme slowness of all geological changes," it is simply a
popular error to regard that as, in any wise, a fundamental and
necessary dogma of uniformitarianism. It is extremely astonishing to
me that any one who has carefully studied Lyell's great work can have
so completely failed to appreciate its purport, which yet is "writ
large" on the very title-page: "The Principles of Geology, being an
attempt to explain the former changes of the earth's surface by
reference to causes now in operation." The essence of Lyell's doctrine
is here written so that those who run may read; and it has nothing to
do with the quickness or slowness of the past changes of the earth's
surface; except in so far as existing analogous changes may go on
slowly, and therefore create a presumption in favour of the slowness
of past changes.

With that epigrammatic force which characterises his style, Buffon
wrote, nearly a hundred and fifty years ago, in his famous "Theorie de
la Terre": "Pour juger de ce qui est arrive, et meme de ce qui
arrivera, nous n'avons qu'a examiner ce qui arrive." The key of the
past, as of the future, is to be sought in the present; and, only when
known causes of change have been shown to be insufficient, have we any
right to have recourse to unknown causes. Geology is as much a
historical science as archaeology; and I apprehend that all sound
historical investigation rests upon this axiom. It underlay all
Hutton's work and animated Lyell and Scope in their successful efforts
to revolutionise the geology of half a centur