a
limited duration, and that, at some period in the past, a condition of the
world, essentially similar to that which we now know, came into existence,
without any precedent condition from which it could have naturally
proceeded. The assumption that successive states of nature have arisen,
each without any relation of natural causation to an antecedent state, is
a mere modification of this second hypothesis.

The third hypothesis also assumes that the present state of things has had
but a limited duration; but it supposes that this state has been evolved
by a natural process from an antecedent state, and that from another, and
so on; and, on this hypothesis, the attempt to assign any limit to the
series of past changes is, usually, given up.

It is so needful to form clear and distinct notions of what is really
meant by each of these hypotheses, that I will ask you to imagine what,
according to each, would have been visible to a spectator of the events
which constitute the history of the earth. On the first hypothesis,
however far back in time that spectator might be placed, he would see a
world essentially, though perhaps not in all its details, similar to that
which now exists. The animals which existed would be the ancestors of
those which now live, and similar to them; the plants, in like manner,
would be such as we know; and the mountains, plains, and waters would
foreshadow the salient features of our present land and water. This view
was held more or less distinctly, sometimes combined with the notion of
recurrent cycles of change, in ancient times; and its influence has been
felt down to the present day.

It is worthy of remark that it is a hypothesis which is not inconsistent
with the doctrine of Uniformitarianism, with which geologists are
familiar. That doctrine was held by Hutton, and in his earlier days by
Lyell. Hutton was struck by the demonstration of astronomers that the
perturbations of the planetary bodies, however great they may be, yet
sooner or later right themselves; and that the solar system possesses a
self-adjusting power by which these aberrations are all brought back to a
mean condition. Hutton imagined that the like might be true of terrestrial
changes; although no one recognized more clearly than he the fact that the
dry land is being constantly washed down by rain and rivers, and deposited
in the sea; and that thus, in a longer or shorter time, the inequalities
of the earth's surface mu