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Show 566 CORAL F OH.MA'l'IONS. April, 1836. best characterized of these, namely, the Maldive islands, extend in length for 480 miles, with an average breadth of sixty. These atolls agree in most respects with the lagoons of the Pacific; they differ, however, in several. of them being crowded together-such little groups being separated from other groups by profoundly deep channels. Now if we look in a chart, at the prolongation of the reef towards the northern end of New Caledonia, and then complete the work of suhsidence, so as to continue producing the same results; we should have the original reef broken up into many patches ; each of which, from the vigorous growth of coral on the out;.. side, would have a constant tendency to assume a rounded form. Every accidental break in the continuity of the first line would determine a fresh circle. In the case, therefore, of the Low or Dangerous Archipelago in the Pacific, I believe that the lagoon islands were moulded round the flanks of so many distinct islands; but in the Maldives, that one single mountainous island, bordered by reefs, and very nearly of the same actual figure and dimensions with New Caledonia, formerly occupied that ·part of the ocean. Lastly, to the extreme westward, the coast of Africa is closely skirted by coral reefs, and according to facts stated in Captain Owen's voyage, has probably been uplifted within a recent period. The same remark applies to the northern part of Madagascar, and, judging from the reefs likewise at the Seychelles, situateq on the submarine prolongation of that great island. Between these two, N.N.E. and S.S.W. lines of elevation, some lagoon and widely-encircled islands indicate a band of subsidence. When we consider the absence both of widely-encircling reefs and lagoon islands in the several archipelagoes and wide areas, where there are proofs of elevations ; and on the other hand the converse case of the absence of such proof where reefs of those classes do occur; together with the juxtaposition of the different kinds produced by movements of the same order, and the symmetry of the whole, I think it will be difficult (even independently of the explanation it April, 1836. CORAL FOU.MA'l'IONS. 567 offers of the peculiar configuration of each class) to deny a great probability to this theory. Its importance, if true, is evident; because we get at one glance an insight into the system by which the surface of the land has been broken up, in a manner somewhat similar, but certainly far less perfect, to what a geologist would have done who had lived his ten thousand years, and kept a record of the passing changes. We see the law almost established, that linear areas of great extent undergo movements o.f an astonishing uniformity, and that the bands of elevation and subsidence alternate. Such phenomena at once impress the mind with the idea of a fluid most gradually propelled onwards, from beneath one part of the solid crust to another. I cannot at present do more than allude to some of the results which may be deduced from these views. If we examine the points of eruption over the Pacific and Indian oceans, we shall find that all the active volcanoes occur within tlte areas of elevation. (The Asiatic band must be excepted; inasmuch as we are entirely in want of information of all kinds respecting it.) On the other hand, in the great spaces supposed to be now subsiding, between the Radack and Dangerous Archipelagoes,in the Corallian sea, and among the atolls which front the west coast of India, not one occurs. If we look at the changes of level as a consequence of the propulsion of fluid matter beneath the crust, as before suggested, then the area to which the force is directed might be expected to yield more readily than that whence it was gradually retiring. I am the more convinced that the above law is true, because, if we look to other parts of the world, proofs of recent elevation almost invariably occur, where there ar.e active vents: I may instance the West Indies, the Cape de Verds, Canary Islands, southern Italy, Sicily, and other places. But in answer to this, those geologists, who, judging from the history of the isolated volcanic mounds of Europe, were inclined to believe that the level of the ground was constantly oscillating up and down, might maintain that on these same areas, the amount of subsidence had been equal to that |