This theory is supported by a vast amount of curious and ingenious reasoning. In the first place, there is nothing more remarkable in the physical conformation of the Globe, than the immense predominance of water over land throughout those extensive tracts of ocean where Coral Reefs abound. Now this is just what we should naturally expect if the hypothesis of Mr. Darwin were admitted; for wherever the Crust of the Earth has been subsiding for many ages on a large scale, the domain of the sea must of necessity have been considerably enlarged, and that of the land contracted in proportion. Again, this hypothesis will be found to harmonize most perfectly with all the phenomena of Fringing Reefs, Barrier Reefs, Encircling Reefs, and Lagoon Islands. The Fringing Reef represents, as it were, the first stage of progress. The building operations have just commenced near the shore of some island or continent, and but little space intervenes between the land and the incrusting wall of coral. Then, as the Crust of the Earth gradually subsides, the water encroaches on the land, and forms a channel between it and the reef. Meanwhile the Zoophytes are at work, and the coral rock is growing upward as the foundation on which it rests is sinking downward: each year it is higher from the bed of the sea, and yet no nearer to the surface of the waters. And when at length the channel, which is ever growing wider and wider, has reached a certain limit, the Fringing Reef becomes a Barrier Reef, or if it encompasses an island, an Encircling Reef. Lastly, the Encircling Reef will finally become a Lagoon Island, when the highest peaks of the land it encloses have slowly disappeared beneath the surface of the waters. In confirmation of this reasoning Mr. Darwin has pointed out numerous examples to illustrate each intermediate stage through which, according to his hypothesis, the Coral Reef must pass in the progress of its construction. He traces the gradual transition from the low bank of coral incrusting a rocky shore to the Encircling Reef that compasses round a lofty island, like Tahiti, with a broad channel between. Then he shows how this channel insensibly becomes wider and wider, encroaching more and more upon the land, until at length only a few high peaks remain above water. Finally he leads us on to the case of a perfect Atoll, within which no trace of land remains to be seen; and the channel, now become a lagoon, is encompassed by a Reef of Coral Rock that rises steeply from an unfathomed ocean.