MARK TWAIN
those which Mr. Darwin propounded. In 1858 Mr. Wallace, who was then engaged in studying the natural history of the Malay Archipelago, sent to Mr. Darwin (as the man most likely to understand him) a paper in which he sketched the outlines of a theory identical with that upon which Mr. Darwin had so long been at work. The same sequence of observed facts and infer ences that had led Mr. Darwin to the discovery of natural selection and its consequences had led Mr. Wallace to the very threshold of the same discovery; but in Mr. Wallace s mind the theory had by no means been wrought out to the same degree of completeness to which it had been wrought in the mind of Mr. Darwin. In the preface to his charming book on Natural Selection, Mr. Wallace, with rare modesty and candor, acknowl edges that whatever value his speculations may have had, they have been utterly surpassed in richness and cogency of proof by those of Mr. Darwin. This is no doubt true, and Mr. Wallace has done such good work in further illustration of the theory that he can well afford to rest content with the second place in the first announcement of it.
The coincidence, however, between Mr. Wallace s conclu sions and those of Mr. Darwin was very remarkable. But, after all, coincidences of this sort have not been uncommon in the history of scientific inquiry. Nor is it at all surprising that they should occur now and then, when we remember that a great and pregnant discovery must always be concerned with some question which many of the foremost minds in the world are busy thinking about. It was so with the discovery of the differential calculus, and again with the discovery of the planet Neptune. It was so with the interpretation of the Egyptian hieroglyphics, and with the establishment of the undulatory theory of light. It was so, to a considerable extent, with the introduction of the new chemistry, with the discovery of the mechanical equivalent of heat, and the whole doctrine of the correlation of forces. It was so with the invention of the electric telegraph and with the discovery of spectrum analysis. And it is not at all strange that it should have been so with the doctrine of the origin of species through natural selection.
He thinks these "coincidences" were apt to hap pen because the matters from which they sprang
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