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There is scarcely any living coral on it, even on the outer margin, as I have been particularly assured by Captain Moresby; it is, in fact, a wall of dead coral-rock, having the same width and transverse section with the reef in its ordinary state, of which it is a continuous portion.
The united lengths of these volcanic belts is about ninety degrees, or one-fourth of the entire circumference of the globe. Their width is about fifty miles; but, for a space of two hundred miles on each side of them, evidences of subterranean action are to be found in recently elevated coral-rock, or in barrier coral-reefs, indicating recent submergence.
I can hardly explain the reason, but there is to my mind much grandeur in the view of the outer shores of these lagoon-islands. There is a simplicity in the barrier-like beach, the margin of green bushes and tall cocoa-nuts, the solid flat of dead coral-rock, strewed here and there with great loose fragments, and the line of furious breakers, all rounding away towards either hand.
These knolls of coral-rock were evidently once separate reefs in the lagoon of an atoll. Mr. Martens, at Sydney, informed me that this island is surrounded by a terrace-like plain at about the height of a hundred feet, which probably marks a pause in its elevation. From these facts we may infer, perhaps, that the Cook and Austral Islands have been upheaved at a period probably not very remote.
EOUA. I cannot make out from Captain Cook's charts and descriptions, that this island has any reef, although the bottom of the neighbouring sea seems to be corally, and the island itself is formed of coral-rock. I have therefore classed it with the fringed islands and coloured it red.
HALF-MOON SHOAL has a similar structure; Captain D. Ross describes it, as a narrow belt of coral-rock, "with a basin of deep water in the centre," and deep sea close outside. These three shoals I have coloured blue. The PARAQUAS SHOALS are of a circular form, with deep gaps running through them; not coloured.
On one of the Maldiva atolls, Captain Moresby bored to a depth of twenty-six feet, when his auger also broke: he has had the kindness to give me the matter brought up; it is perfectly white, and like finely triturated coral-rock.
The sights of Honolulu had not lost their novelty the tropical foliage of palm, banana, bread-fruit, monkey-pod and algaroba trees; the dark-skinned, brightly-clad natives with flowers on their heads, who walked with bare feet and stately tread along the shady sidewalks or tore through the streets on horseback; the fine stone or wooden residences with wide cool verandas, or humbler native huts surrounded by walls of coral-rock instead of fences; the deep indigo-blue ocean on one hand and the rich green mountains on the other, dripping with moisture and alternately dark and bright with the gloom of clouds and the glory of rainbows, still wore for me their original freshness and interest when I received an urgent request to come to Waialua, a little village on the other side of the island.
None of these remains have been specifically examined. On the coast, where masses of coral-rock would have afforded the clearest evidence, I looked in vain for any signs of recent elevation. For references to the above authorities, and for more detailed reasons for not believing that Tahiti has been recently elevated, I must refer to the "Structure and Distribution of Coral-Reefs."
Paul's, and Fernando Noronha, are, also, entirely without reefs, although they lie far out at sea, are composed of the same ancient volcanic rocks, and have the same general form, with those islands in the Pacific, the shores of which are surrounded by gigantic walls of coral-rock. With the exception of Bermuda, there is not a single coral-reef in the central expanse of the Atlantic Ocean.
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