Undoubtedly Darwin's intellect was fundamentally speculative. We have seen how in the book on _Variation under Domestication_ his affection clung to Pangenesis, perhaps the most questionable part of its contents. He was restless under the sense of an unexplained fact, and thankful for even a provisional explanation. He notes the effect upon him of the discovery that science cannot remain content with facts alone. Geologising with Sedgwick in North Wales, he heard about a tropical shell which had been picked up in a neighbouring quarry. 'I told Sedgwick of the fact, and he at once said (no doubt truly) that it must have been thrown away by some one into the pit; but then added, if really embedded there it would be the greatest misfortune to geology, as it would overthrow all that we know about the superficial deposits of the Midland Counties.... I was then utterly astonished at Sedgwick not being delighted at so wonderful a fact as a tropical shell being found near the surface in the middle of England. Nothing before had ever made me thoroughly realise, though I had read various scientific books, that science consists in grouping facts so that general laws or conclusions can be drawn from them.' It is this conception that he kept steadily before his eyes, and his glory lies in his success in drawing general laws from his facts. [Sidenote: Alfred Russel Wallace (1822).] The work of the other evolutionists, so far as it is not technical rather than literary, is almost accounted for when Darwin's is described. With respect to one indeed, Mr. Alfred Russel Wallace, an inevitable injustice is done whatever course be pursued. He is the co-discoverer with Darwin of the scheme of evolution associated with the name of the latter; and though the fame has gone to the elder man, it seems clear that if not Darwin then Mr. Wallace was destined to stir the mind of the age with this great conception. Mr. Wallace has been an extensive traveller; he published, in 1853, a volume of _Travels on the Amazon_, giving an account of journeys in that region during part of which he was the companion of Mr. Henry Walter Bates, whose _Naturalist on the Amazon_ (1863) is well known as one of the most interesting and valuable books of travel and natural history in the language. It was however his observations in the Malay Archipelago that led Mr. Wallace to the theory of evolution, and perhaps he is best known by his book, _The Malay Archipelago_ (1869). CHAPTER IX. CRITICISM, SCHOLARSHIP, AND MISCELLANEOUS PROSE.