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By J.W. JUDD, C.B., LL.D., F.R.S.

(Mr Francis Darwin has related how his father occasionally came up from Down to spend a few days with his brother Erasmus in London, and, after his brother's death, with his daughter, Mrs Litchfield. On these occasions, it was his habit to arrange meetings with Huxley, to talk over zoological questions, with Hooker, to discuss botanical problems, and with Lyell to hold conversations on geology. After the death of Lyell, Darwin, knowing my close intimacy with his friend during his later years, used to ask me to meet him when he came to town, and "talk geology." The "talks" took place sometimes at Jermyn Street Museum, at other times in the Royal College of Science, South Kensington; but more frequently, after having lunch with him, at his brother's or his daughter's house. On several occasions, however, I had the pleasure of visiting him at Down. In the postscript of a letter (of April 15, 1880) arranging one of these visits, he writes: "Since poor, dear Lyell's death, I rarely have the pleasure of geological talk with anyone.")

In one of the very interesting conversations which I had with Charles Darwin during the last seven years of his life, he asked me in a very pointed manner if I were able to recall the circumstances, accidental or otherwise, which had led me to devote myself to geological studies. He informed me that he was making similar inquiries of other friends, and I gathered from what he said that he contemplated at that time a study of the causes producing SCIENTIFIC BIAS in individual minds. I have no means of knowing how far this project ever assumed anything like concrete form, but certain it is that Darwin himself often indulged in the processes of mental introspection and analysis; and he has thus fortunately left us--in his fragments of autobiography and in his correspondence--the materials from which may be reconstructed a fairly complete history of his own mental development.

There are two perfectly distinct inquiries which we have to undertake in connection with the development of Darwin's ideas on the subject of evolution:

FIRST. How, when, and under what conditions was Darwin led to a conviction that species were not immutable, but were derived from pre-existing forms?

SECONDLY. By what lines of reasoning and research was he brought to regard "natural selection" as a vera causa in the process of evolution?

It is the first of these inquiries which specially interests the geologist; though geology undoubtedly played a part--and by no means an insignificant part--in respect to the second inquiry.

When, indeed, the history comes to be written of that great revolution of thought in the nineteenth century, by which the doctrine of evolution, from being the dream of poets and visionaries, gradually grew to be the accepted creed of naturalists, the paramount influence exerted by the infant science of geology--and especially that resulting from the publication of Lyell's epoch-making work, the "Principles of Geology"--cannot fail to be regarded as one of the leading factors. Herbert Spencer in his "Autobiography" bears testimony to the effect produced on his mind by the recently published "Principles", when, at the age of twenty, he had already begun to speculate on the subject of evolution (Herbert Spencer's "Autobiography", London, 1904, Vol. I. pages 175-177.); and Alfred Russel Wallace is scarcely less emphatic concerning the part played by Lyell's teaching in his scientific education. (See "My Life; a record of Events and Opinions", London, 1905, Vol. I. page 355, etc. Also his review of Lyell's "Principles" in "Quarterly Review" (Vol. 126), 1869, pages 359-394. See also "The Darwin-Wallace Celebration by the Linnean Society" (1909), page 118.) Huxley wrote in 1887 "I owe more than I can tell to the careful study of the "Principles of Geology" in my young days." ("Science and Pseudo Science"; "Collected Essays", London, 1902, Vol. V. page 101.) As for Charles Darwin, he never tired--either in his published writings, his private correspondence or his most intimate conversations--of ascribing the awakening of his enthusiasm and the direction of his energies towards the elucidation of the problem of development to the "Principles of Geology" and the personal influence of its author. Huxley has well expressed what the author of the "Origin of Species" so constantly insisted upon, in the statements "Darwin's greatest work is the outcome of the unflinching application to Biology of the leading idea and the method applied in the "Principles" to Geology ("Proc. Roy. Soc." Vol. XLIV. (1888), page viii.; "Collected Essays" II. page 268, 1902.), and "Lyell, for others, as for myself, was the chief agent in smoothing the road for Darwin." ("Life and Letters of Charles Darwin" II. page 190.)