ers according to a certain law up to a particular
point, and then, most unexpectedly, perhaps even unaccountably, the law
of the series is changed, and the next term exhibits a striking
departure from the order previously followed; and so, it is argued, it
may be in nature. Each organism may propagate after its kind for immense
periods, so as to give the impression of this being an invariable law;
but at a certain stage the order may change, and the next term in the
series may differ from all that went before it. The argument--if it can
be called an argument--amounts to this: Mr. Babbage's machine produces a
_series of numbers, and of numbers only_, but according to different
laws of succession; _ergo_, Nature may produce in the same way, and with
similar variations, _different races of plants and animals_. The
argument would have been perfect if the engine had produced _something
else than numbers_; if, as Professor Dod supposes, "while watching Mr.
Babbage's machine, presenting to us successive numbers by the revolution
of its plates, we should suddenly see one of those plates resolving
itself into types, and these types arranging themselves in the order of
a page of 'Paradise Lost,' or even of 'The Vestiges of Creation;'--in
such a case, there might have been something in the argument; but even
then, the withering question remains, Is there any man in his senses who
would not immediately conclude that _some new cause was now at work_?"

In short, in so far as the _facts of the case_ are concerned, there is
not only no known instance either of "spontaneous generation" or of
"transmutation of species," but there is not even any natural analogy
that can give the theory the slightest aspect of verisimilitude. The
author of "The Vestiges" thinks that a presumption in its favor may be
derived from "the analogy of the inorganic world,"--in other words, from
the supposed conversion of nebulae into planets and astral systems by the
operation of natural causes; but this analogy has been conclusively set
aside by disproving the hypothesis on which it depends. He further
thinks that a favorable presumption may be derived from "the analogy of
the organic world,"--in other words, from the process of propagation by
which the races of plants and animals are perpetuated; but the
presumption thence derived, so far from being favorable, is directly
opposed to his theory, since all the facts which come under our
cognizance in every depar