people.

So, in Geology, if we could assume that it is part of the plan of Nature
to preserve, in every region of the globe, an unbroken series of
monuments to commemorate the vicissitudes of the organic creation, we
might infer the sudden extirpation of species, and the simultaneous
introduction of others, as often as two formations in contact are found
to include dissimilar organic fossils. But we must shut our eyes to the
whole economy of the existing causes, aqueous, igneous, and organic, if
we fail to perceive _that such in not the plan of Nature_.

_Concluding remarks on the identity of the ancient and present system of
terrestrial changes._--I shall now conclude the discussion of a question
with which we have been occupied since the beginning of the fifth
chapter; namely, whether there has been any interruption, from the
remotest periods, of one uniform system of change in the animate and
inanimate world. We were induced to enter into that inquiry by
reflecting how much the progress of opinion in Geology had been
influenced by the assumption that the analogy was slight in kind, and
still more slight in degree, between the causes which produced the
former revolutions of the globe, and those now in every-day operation.
It appeared clear that the earlier geologists had not only a scanty
acquaintance with existing changes, but were singularly unconscious of
the amount of their ignorance. With the presumption naturally inspired
by this unconsciousness, they had no hesitation in deciding at once that
time could never enable the existing powers of nature to work out
changes of great magnitude, still less such important revolutions as
those which are brought to light by Geology. They, therefore, felt
themselves at liberty to indulge their imaginations in guessing at what
_might be_, rather than inquiring _what is_; in other words, they
employed themselves in conjecturing what might have been the course of
nature at a remote period, rather than in the investigation of what was
the course of nature in their own times.

It appeared to them more philosophical to speculate on the possibilities
of the past, than patiently to explore the realities of the present; and
having invented theories under the influence of such maxims, they were
consistently unwilling to test their validity by the criterion of their
accordance with the ordinary operations of nature. On the contrary, the
claims of each new hypothesis to credibility app