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Page:Popular Science Monthly Volume 32.djvu/266

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THE POPULAR SCIENCE MONTHLY.

islands. This may or may not have been often the case in the Pacific. But it does not affect the question, except in so far as it may justify Darwin's conception that reef corals can not grow on "loose deposits." They may have ceased to be so soft and loose as they are when resting in the quiet depths of the thousand-fathoms sea. This induration may be part or an accompaniment of the process of elevation, but whether it be so or not the process is equally one of elevation and not of subsidence. In the island described by Dr. Guppy, the foundations of the reef-building corals are seen resting directly on the remains of the pelagic fauna, and both theories equally assume and assert the uncontested fact that these foundations when the coral wall began to grow must have been previously elevated to the requisite level, that, namely, of from one hundred and eighty to one hundred and twenty feet below the surface of the ocean. Mr. John Murray's explanation is fully confirmed that the coral reefs often begin on shoals; that these shoals are due to elevations of the sea-bottom; that the reef when once established can and does grow seaward upon its own fragments broken and submerged; that these form a "talus" capable of indefinite advance until the farthest limit of the shoal is reached; that the rearward ranks of the coral animals die as they are left behind in the hot and shallow waters of the lagoon; that their calcareous skeletons are then attacked by the solvent action of the water, are eaten away and carried off to form the materials of new reefs and the shells of countless other creatures. These have likewise been confirmed by the investigations of Mr. Alexander Agassiz in the West Indies, Often in the Pacific, as in all other regions of the earth, the elevating forces rest for ages, having done all the work which on some particular area they have got to do. The shoals remain shoals, only covered with the walls and battlements of coral. This is the case which accounts for countless islands never exceeding a certain height. On the other hand, and "otherwhere," the elevating forces, after a rest, resume their operation, lift up these coral walls and battlements wholly out of the sea, and make other islands by the thousand which become the delight of man; while in yet another class of cases the elevations open out into volcanoes, and constitute great areas of land which are among the most fertile regions of the habitable globe. But everywhere and always the ubiquitous coral animals fix on every shoal and on every shore whether old or new, and resume the wonderful cycle of operations in which they are a subordinate but a powerful agent.

In a recent article in this Review I had occasion to refer to the curious power which is sometimes exercised on behalf of certain accepted opinions, or of some reputed prophet, in establishing a sort of Reign of Terror in their own behalf, sometimes in philosophy, sometimes in politics, sometimes in science. This observation was received as I expected it to be—by those who, being themselves sub-