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252 which might have helped Darwin, as it is much needed to help us even now, to conceive it. It is the old doctrine of the science long ago formulated by Hutton, that the work of erosion and of denudation must be equal to the work of deposition. Rocks have been formed out of the ruins of older rocks, and those older rocks must have been worn down and carried off to an equivalent amount. So it is here, with another kind of erosion and another kind of deposition. The coral-building animals can only get their materials from the sea, and the sea can only get its materials by dissolving it from calcareous rocks of some kind. The dead corals are among its greatest quarries. The inconceivable and immeasurable quantities which have been dissolved out of the lagoons and sheltered seas of the Pacific and of the Indian Ocean are not greater than the immeasurable quantities which are again used up in the vast new reefs of growing coral, and in the calcareous covering of an inconceivable number of other marine animals.

Here, then, was a generalization as magnificent as that of Darwin's theory. It might not present a conception so imposing as that of a whole continent gradually subsiding, of its long coasts marked by barrier-reefs, of its various hills and irregularities of surface, marked by islands of corresponding size, and finally of the atolls which are the buoys, indicating where its highest peaks finally disappeared beneath the sea. But, on the other hand, the new explanation was more like the analogies of Nature—more closely correlated with the wealth of her resources, with those curious reciprocities of service, which all her agencies render to each other, and which indicate so strongly the ultimate unity of her designs. This grand explanation we owe to Mr. John Murray, one of the naturalists of the Challenger expedition, a man whose enthusiasm for science, whose sagacity and candor of mind, are not inferior to those of Darwin, and whose literary ability is testified by the splendid volumes of "Reports" now in course of publication under his editorial care. Mr. Murray's new explanation of the structure and origin of coral reefs and islands was communicated to the Royal Society of Edinburgh in 1880, and supported with such a weight of facts, and such a close texture of reasoning, that no serious reply has ever been attempted. At the same time, the reluctance to admit such an error in the great Idol of the scientific world, the necessity of suddenly disbelieving all that had been believed and repeated in every form, for upward of forty years—of canceling what had been taught to the young of more than a whole generation—has led to a slow and sulky acquiescence, rather than to that joy which every true votary of science ought to feel in the discovery of a new truth and—not less—in the exposure of a long-accepted error. Darwin himself had lived to hear of the new solution, and with that splendid candor which was eminent in him, his mind, though now