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Here he stayed for some months, and then, having made a new suit of sails from native mats, he returned to Port Jackson to relate the story of his fateful voyage. About north-west from turbulent and distracted Samoa lie a group of eight low-lying coral atolls, called the Ellice Islands.
Kotzebue has given plans of several; Cook and Bligh mention others; a few were seen during the voyage of the "Beagle"; and notices of other atolls are scattered through several publications. Couthouy; it is an upraised atoll, but as it does not appear to be fringed by living reefs, it is left uncoloured.
I have found that they constitute a new class of reefs, distinct from those described by Darwin and Dana under the name of fringing reefs, barrier reefs, and atolls. I have lately read a paper upon that subject before the American Academy, which I shall send you as soon as it is printed. The case is this.
There is a very good picture, which Professor Roscoe has been kind enough to prepare for me, of one of these atolls, which will enable you to form a notion of it as a landscape. You have in the foreground the waters of the Pacific.
A strictly analogous, but different fact, may be observed at the Maldiva atolls namely, that where two atolls stand in front of each other, the breaches in the reef are the most numerous on their near, and therefore less exposed, sides.
The existence in many parts of the world of high table-land, proves that large surfaces have been upraised in mass to considerable heights above the level of the ocean; although the highest points in almost every country consist of upturned strata, or erupted matter: and from the immense spaces scattered with atolls, which indicate that land originally existed there, although not one pinnacle now remains above the level of the sea, we may conclude that wide areas have subsided to an amount, sufficient to bury not only any formerly existing table-land, but even the heights formed by fractured strata, and erupted matter.
In most respects, there is a perfect resemblance with ordinary islands in the grouping of atolls and in their form: thus the outline of all the larger groups is elongated; and the greater number of the individual atolls are elongated in the same direction with the group, in which they stand.
Thus have we traced the history of these great rings of coral-rock, from their first origin through their normal changes, and through the occasional accidents of their existence, to their death and final obliteration. In my volume on "Coral Formations" I have published a map, in which I have coloured all the atolls dark-blue, the barrier-reefs pale-blue, and the fringing reefs red.
Atolls, or Coral Islands Their strange Appearance Their Connexion with Volcanoes Their Mode of Formation Antarctic Volcanoes Diatomaceous Deposits To the southward of the Sandwich Islands, on the other side of the equator, there is a large group of islands in the Pacific, which have a very peculiar appearance. They are called Atolls or Coral Islands.
If his view be correct, it is clear that neither atolls, nor encircling reefs, should be found in those portions of the ocean in which we have reason to believe, on independent grounds, that the sea-bottom has long been either stationary, or slowly rising.
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