Coral Reefs

Coral Reefs

The object of this volume is to describe from my own observation and the works of others, the principal kinds of coral-reefs, more especially those occurring in the open ocean, and to explain the origin of their peculiar forms. I do not here treat of the polypifers, which construct these vast works, except so far as relates to their distribution, and to the conditions favourable to their vigorous growth. Without any distinct intention to classify coral-reefs, most voyagers have spoken of them under the following heads: lagoon-islands, or atolls, barrier or encircling reefs, and fringing or shore-reefs. The lagoon-islands have received much the most attention; and it is not surprising, for every one must be struck with astonishment, when he first beholds one of these vast rings of coral-rock, often many leagues in diameter, here and there surmounted by a low verdant island with dazzling white shores, bathed on the outside by the foaming breakers of the ocean, and on the inside surrounding a calm expanse of water, which from reflection, is of a bright but pale green colour. The naturalist will feel this astonishment more deeply after having examined the soft and almost gelatinous bodies of these apparently insignificant creatures, and when he knows that the solid reef increases only on the outer edge, which day and night is lashed by the breakers of an ocean never at rest. Well did Franois Pyrard de Laval, in the year 1605, exclaim, Cest une merueille de voir chacun de ces atollons, enuironn dun grand banc de pierre tout autour, ny ayant point dartifice humain. The accompanying sketch of Whitsunday island, in the South Pacific, taken from Captain Beecheys admirable Voyage, although excellent of its kind, gives but a faint idea of the singular aspect of one of these lagoon-islands. Whitsunday Island is of small size, and the whole circle has been converted into land, which is a comparatively rare circumstance. As the reef of a lagoon-island generally supports many separate small islands, the word island, applied to the whole, is often the cause of confusion; hence I have invariably used in this volume the term atoll, which is the name given to these circular groups of coral-islets by their inhabitants in the Indian Ocean, and is synonymous with lagoon-island. Barrier-reefs, when encircling small islands, have been comparatively little noticed by voyagers; but they well deserve attention. In their structure they are little less marvellous than atolls, and they give a singular and most picturesque character to the scenery of the islands they surround. In the accompanying sketch, taken from the Voyage of the Coquille, the reef is seen from within, from one of the high peaks of the island of Bolabola.[1] Here, as in Whitsunday Island, the whole of that part of the reef which is visible is converted into land. This is a circumstance of rare occurrence; more usually a snow-white line of great breakers, with here and there an islet crowned by cocoa-nut trees, separates the smooth waters of the lagoon-like channel from the waves of the open sea. The barrier-reefs of Australia and of New Caledonia, owing to their enormous dimensions, have excited much attention: in structure and form they resemble those encircling many of the smaller islands in the Pacific Ocean. ......Buy Now (To Read More)

Product details

Ebook Number: 2690
Author: Darwin, Charles
Release Date: Jun 1, 2001
Format: eBook
Language: English