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explained by the present unless good cause can be shown to the contrary; and the fact that, so far as our knowledge of the past history of life on our globe goes, no such cause can be shown—I can not but believe that Lyell was, for others, as for myself, the chief agent in smoothing the road for Darwin. For consistent uniformitarianism postulates evolution as much in the organic as the inorganic world. The origin of a new species by other than ordinary agencies would be a vastly greater "catastrophe" than any of those which Lyell successfully eliminated from sober geological speculation."

But however much Lyell may have "smoothed the road," Huxley, and most of the biologists of those thirty years, declined to go in thereat. It remained for an anonymous amateur, whom they thereupon with one accord fell to abusing, to point out the practicability of that highway. In the "Vestiges" and the "Explanations" Chambers urged the presumption from geological uniformitarianism with an effective use of concrete examples.

It is a curious circumstance, however, that the argument from uniformitarianism cut both ways. As Wallace says:

This difference, as Darwin said in the "Origin," seemed, on the face of it, "to make a broad and clear distinction between varieties and species." And the apparent existence of such a radical distinction between the varieties produced under domestication and true physiological species was an objection, not only against natural selection, but also against evolution itself; for it meant that we do not see now, nor within the limits of human observation, organisms actually getting