h special formations are so strikingly
characterized by some predominating type of life as to justify such
expressions as the age of mollusks, the age of reptiles, the age of
mammals, the introduction of the new-comers did not take place abruptly.
as by sudden creation. They gradually emerged in an antecedent age,
reached their culmination in the one which they characterize, and then
gradually died out in a succeeding. There is no such thing as a
sudden creation, a sudden strange appearance--but there is a slow
metamorphosis, a slow development from a preexisting form. Here again
we encounter the necessity of admitting for such results long periods
of time. Within the range of history no well-marked instance of such
development has been witnessed, and we speak with hesitation of doubtful
instances of extinction. Yet in geological times myriads of evolutions
and extinctions have occurred.

Since thus, within the experience of man, no case of metamorphosis
or development has been observed, some have been disposed to deny its
possibility altogether, affirming that all the different species have
come into existence by separate creative acts. But surely it is less
unphilosophical to suppose that each species has been evolved from a
predecessor by a modification of its parts, than that it has suddenly
started into existence out of nothing. Nor is there much weight in
the remark that no man has ever witnessed such a transformation taking
place. Let it be remembered that no man has ever witnessed an act
of creation, the sudden appearance of an organic form, without any
progenitor.

Abrupt, arbitrary, disconnected creative acts may serve to illustrate
the Divine power; but that continuous unbroken chain of organisms which
extends from palaeozoic formations to the formations of recent times, a
chain in which each link hangs on a preceding and sustains a succeeding
one, demonstrates to us not only that the production of animated beings
is governed by law, but that it is by law that has undergone no change.
In its operation, through myriads of ages, there has been no variation,
no suspension.

The foregoing paragraphs may serve to indicate the character of a
portion of the evidence with which we must deal in considering the
problem of the age of the earth. Through the unintermitting labors of
geologists, so immense a mass has been accumulated, that many volumes
would be required to contain the details. It is drawn from the pheno