llated back again. But if this be
the real significance of the seemingly sudden change from stratum to
stratum, then the whole case for catastrophism is hopelessly lost; for
such breaks in the strata furnish the only suggestion geology can offer
of sudden and catastrophic changes of wide extent.

Let us see how Lyell elaborates these ideas, particularly with reference
to the rotation of species.(2)

"I have deduced as a corollary," he says, "that the species existing at
any particular period must, in the course of ages, become extinct, one
after the other. 'They must die out,' to borrow an emphatic expression
from Buffon, 'because Time fights against them.' If the views which I
have taken are just, there will be no difficulty in explaining why
the habitations of so many species are now restrained within exceeding
narrow limits. Every local revolution tends to circumscribe the range
of some species, while it enlarges that of others; and if we are led
to infer that new species originate in one spot only, each must require
time to diffuse itself over a wide area. It will follow, therefore, from
the adoption of our hypothesis that the recent origin of some species
and the high antiquity of others are equally consistent with the general
fact of their limited distribution, some being local because they have
not existed long enough to admit of their wide dissemination; others,
because circumstances in the animate or inanimate world have occurred to
restrict the range within which they may once have obtained....

"If the reader should infer, from the facts laid before him, that the
successive extinction of animals and plants may be part of the constant
and regular course of nature, he will naturally inquire whether there
are any means provided for the repair of these losses? Is it possible as
a part of the economy of our system that the habitable globe should to a
certain extent become depopulated, both in the ocean and on the land, or
that the variety of species should diminish until some new era arrives
when a new and extraordinary effort of creative energy is to be
displayed? Or is it possible that new species can be called into being
from time to time, and yet that so astonishing a phenomenon can escape
the naturalist?

"In the first place, it is obviously more easy to prove that a species
once numerously represented in a given district has ceased to be
than that some other which did not pre-exist had made its
appearanc