Darwin's hypothesis and the facts on which it was based have become so familiar that students sometimes express surprise that so much praise has been awarded to the author. The conditions as presented in his discussion are so clear that certainly no man could reach any other conclusion. That is true, but it is true only because Darwin marshalled his facts in a manner so masterly; in any event, it is always easy to do a thing when another has done it well and told us how. But it must be remembered that an hypothesis of this sort, though normal enough in our day, was very abnormal in that day; indeed, it was contrary to Darwin's own underlying conceptions, for, though a uniformitarian, he had seen many phenomena which, for a time, made him only a halting disciple. Yet his hypothesis was a monumental contribution in support of the uniformitarian doctrine, which, under the leadership of Lyell, was gaining sturdy adherents. That the hypothesis met with uncompromising opposition need not be said. The material of coral origin extended to vast depths alongside of the islands, in some cases apparently to 4,000 feet. The upward growth of the reef was known to be extremely slow. If the subsidence and the upward growth kept pace, as was essential to the hypothesis, evidently the required period, belonging to the latest portion of the earth's existence, was immensely long. It is difficult now to understand how great moral courage was needed by the man who published such a doctrine; sixty years ago, the educated man of Great Britain had not learned to distinguish between faith and prejudice.
This effort to explain the origin of coral reefs has been regarded, justly, as Darwin's especial contribution to geology. It has been opposed strenuously by careful students during the last twenty years and even now it is a bone of contention; but the most strenuous opponent concedes that it is logical and a fair induction from the facts as then known. Be it true or not, be it a competent explanation or not, no matter. In influence on geology it has been as far-reaching as the doctrine of natural selection has been on biology. It involves every important problem in dynamics of the earth's crust; in testing it, men have been led into paths of investigation, which, but for Darwin, might still be untrodden. The influence went farther. The hypothesis was presented at a time when men's minds were warped by prejudice, when men were extremists, when too many were defenders of dogmas in science and too few were searchers after truth. Darwin's discussion was a model of frankness; suggestions offered by his predecessors were dealt with courteously; he searched far and wide for objections to his own suggestions, and when objections were found he stated them in detail, concealing nothing and urging further investigation. His conclusions were, for him, merely tabulations of observed facts. One can not overestimate the importance of this method; it was a chief factor in chang-