Page:Quarterly Journal of the Geological Society of London, vol. 25.djvu/400

304 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [May 26, of supporting a scanty vegetation of weeds, coarse grass and creepers, but sometimes, as at Cairncross, the Howicks, Pipers, and many others, a dense scrub and well-grown Mangroves, Casuarinae, Pandani, Pisoniae, and other trees common along this coast. Of this organic rock the beacon on Raine Island was built eighteen or nineteen years ago; and the durability of the material is shown by the fact that the structure has hitherto undergone no decay from weathering. It doubtless tops some crystalline formation on which it has been slowly reared. Still it is evident that, though now permanently out of, it must have been formed well under water, and have reached the surface at low water with the zoophytes which built it in full activity, when the greater part of the long reef now in full activity at the sea-level at ebb, and of which it forms only a fractional part, was still many feet below. And now, when the latter has reached close to the surface at low water, the former projects 20 feet into the air; but denuded by weathering of its soft and brittle exterior, with its dense solid interior laid bare, and its living many-hued branching madrepores replaced by less gaudy forms of vegetable life.

3rd. Between the active coral-reef still under water; and the extinct ones now well raised above it, like Raine Island, we meet with many intermediate forms, occasionally as islets, which consist of a sand-bank just showing above the surface, and either still unclad with vegetation or having a few sprouts of mangrove, the hardiest of trees, and usually the first to find a footing in the coarse coral debris, little capable, to all appearance, of sustaining life of any sort; while others show greater elevation, and both a more extensive and better-clad area. In short, we find islands of this class in many different stages of upward progress, sometimes forming part of the reef, but more usually lying between it and the mainland, when they occasionally interfere materially with the navigation of the inner passage from being difficult to detect in the bright glare of the sun until the vessel is too close to them to be consistent with her safety.

Besides the above, other indications of the gradual rising of this coast may not improbably be found on a more careful survey of the land than could be afforded during the rapid passages of H.M.S. 'Salamander' up and down, when landing was effected only occasionally and for periods too brief to be of much avail for geological purposes. The elevation of Eastern Australia is going on very slowly, because the forces which are at least connected in some way with, if they do not actually induce it, are not in the island itself, but distant, and centred either in New Zealand, New Caledonia, the Indian archipelago, or the still more remote volcanic districts of the South Pacific. These facts, taken in connexion with the recent discovery by Bickmore, an American geologist, that the eastern coast of Asia, and especially China and Japan, is also rising, and doubtless more rapidly, like the opposite coast of South America, while the bed of the South Pacific is slowly subsiding, cannot fail to be interesting to scientific men, whether or not they accept Pre-