We are told, indeed, in answer to this argument, that Mr. Babbage's engine produces numbers 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 department of Nature serve only to establish the two great maxims of Natural History,--that _organic life can spring only from organic life_, and that _like produces like, both in the vegetable and animal world_.