- [Footnote: crater, is opposed by their great dimensions, the diameters
of many of them being 30, 40, and sometimes even 60 geographical miles. Our fire-emitting mountains have no such craters; and if we would compare the lagoon, with its submerged interior and narrow enclosing reef, to one of the annular mountains of the moon, we must not forget that those lunar mountains are not volcanoes, but wall-surrounded districts. According to Darwin, the process of formation is the following:—He supposes a mountainous island surrounded by a coral-reef, (a "fringing reef" attached to the shore), to undergo subsidence: the "fringing reef" which subsides with the island is continually restored to its level by the tendency of the coral-animals to regain the surface of the sea, and becomes thus, as the island gradually sinks and is reduced in size, first an "encircling reef" at some distance from the included islet, and subsequently, when the latter has entirely disappeared, an atoll. According to this view, in which islands are regarded as the culminating points of a submerged land, the relative positions of the different coral islands would disclose to us that which we could hardly learn by the sounding line, concerning the configuration of the land which was above the surface of the sea at an earlier epoch. The entire elucidation of this attractive subject, (to the connection of which with the migrations of plants and the diffusion of races of men attention was called at the commencement of the present note), can only be hoped for when inquirers shall have succeeded in obtaining greater knowledge than is now possessed of the depth and the nature of the rocks on which the lowest strata of the dead corals rest.]
