divisions, Primary, Secondary and Tertiary, are of
absolute and uniform application; that these great divisions are
separable into subdivisions, each of which is definitely distinguishable
from the rest, and is everywhere recognizable by its characters as such
or such; and that in all parts of the Earth, these minor systems
severally began and ended at the same time. When they meet with the term
"Carboniferous era," they take for granted that it was an era
universally carboniferous--that it was, what Hugh Miller indeed actually
describes it, an era when the Earth bore a vegetation far more luxuriant
than it has since done; and were they in any of our colonies to meet
with a coal-bed, they would conclude that, as a matter of course, it was
of the same age as the English coal-beds.

Now this belief that geologic "systems" are universal, is no more
tenable than the other. It is just as absurd when considered _a priori_;
and it is equally inconsistent with the facts. Though some series of
strata classed together as Oolite, may range over a wider district than
any one stratum of the series; yet we have but to ask what were the
circumstances under which it was deposited, to see that the Oolitic
series, like one of its individual strata, must be of local origin; and
that there is not likely to be anywhere else, a series which
corresponds, either in its characters or in its commencement and
termination. For the formation of such a series implies an area of
subsidence, in which its component beds were thrown down. Every area of
subsidence is necessarily limited; and to suppose that there exist
elsewhere groups of beds completely answering to those known as Oolite,
is to suppose that, in contemporaneous areas of subsidence, like
processes were going on. There is no reason to suppose this; but good
reason to suppose the reverse. That in contemporaneous areas of
subsidence throughout the globe, the conditions would cause the
formation of Oolite, is an assumption which no modern geologist would
openly make. He would say that the equivalent series of beds found
elsewhere, would probably be of dissimilar mineral character. Moreover,
in these contemporaneous areas of subsidence, the processes going on
would not only be different in kind; but in no two cases would they be
likely to agree in their commencements and terminations. The
probabilities are greatly against separate portions of the Earth's
surface beginning to subside at the sa