inference which was widely drawn by the enemies of evolution from the arguments of Sir William Thomson was that if geologists had overestimated the age of the cooled earth there was not time for the evolution of animals and plants to have taken place.  Huxley pointed out a fact which should be quite obvious, but which even yet is frequently neglected.  The evidence for the gradual appearance of life in the past history of the earth depends simply on the fact that the successive forms of life appear in successive strata, and the length of time taken for these changes simply depends upon the length of time which was taken up by the formation of the strata.  Our only reason for supposing the evolution of life, made plain by fossil records, to have taken place very slowly is that geologists have stated that the deposition of the strata took place very slowly.  Whether these strata were deposited slowly or less slowly, we know that the forms of life changed at the same rate.

“Biology takes her time from geology.  The only reason we have for believing in the slow rate of change in living forms is the fact that they persist through a series of deposits which, geology informs us, have taken a long while to make.  If the geological clock is wrong, all the naturalist will have to do is to modify his notion of the rapidity of change accordingly; and I venture to point out that, when we are told that the limitation of the period during which living beings have inhabited this planet to one, two, or three hundred million years requires a complete revolution in geological speculation, the onus probandi rests on the maker of the assertion, who brings forward not a shadow of evidence in its support.”

Perhaps, although this is now an old controversy, it is worth while to recall that the keenness of Huxley’s language was not directed against Sir William Thomson, between whom and Huxley there was no more than the desire to argue out an interesting scientific question upon which their conclusions differed, but between Huxley and those outsiders who were always ready to turn any dubious question in science into an argument discrediting the general conclusions of science.

The last time that Huxley occupied the Presidential Chair of the Geological Society was in 1870, and he occupied his Presidential address by a review of the “old judgments” which he had given in the course of his first address in 1862.  The address was entitled “Palaeontology and Evolution,” and the most important part of it was a complete withdrawal of the fears he had expressed that geology would not supply definite evidence of the transformation of species.  Important discoveries had come thick and fast; and, at least in the case of the higher vertebrates, he declared that, however one might “sift and criticise them,” they left a clear balance in favour of the doctrine of the evolution of living forms one from another.  But, with his usual critical spirit,