Coral Reefs

Page 96

This island is a likeness on a grand scale to the Gambier group in the Low Archipelago. Of the groups of low (In D'Urville and Lottin's chart, Peserare is written with capital letters; but this evidently is an error, for it is one of the low islets on the reef of Namonouyto (see Lutke's charts)--a regular atoll.) islands forming the chief part of the Caroline Archipelago, all those of larger size, have the true atoll-structure (as may be seen in the "Atlas" by Captain Lutke), and some even of the very small ones, as MACASKILL and DUPERREY, of which plans are given in the "Atlas of the 'Coquille's' Voyage." There are, however, some low small islands of coral-formation, namely OLLAP, TAMATAM, BIGALI, SATAHOUAL, which do not contain lagoons; but it is probable that lagoons originally existed, but have since filled up: Lutke (volume ii., page 304) seems to have thought that all the low islands, with only one exception, contained lagoons. From the sketches, and from the manner in which the margins of these islands are engraved in the "Atlas of the Voyage of the 'Coquille'," it might have been thought that they were not low; but by a comparison with the remarks of Lutke (volume ii., page 107, regarding Bigali) and of Freycinet ("Hydrog. Memoir 'L'Uranie' Voyage," page 188, regarding Tamatam, Ollap, etc.), it will be seen that the artist must have represented the land incorrectly. The most southern island in the group, namely PIGUIRAM, is not coloured, because I have found no account of it. NOUGOUOR, or MONTE VERDISON, which was not visited by Lutke, is described and figured by Mr. Bennett ("United Service Journal," January 1832) as an atoll. All the above-mentioned islands have been coloured blue.


FAIS Island is ninety feet high, and is surrounded, as I have been informed by Admiral Lutke, by a narrow reef of living coral, of which the broadest part, as represented in the charts, is only 150 yards; coloured red.-- PHILIP Island., I believe, is low; but Hunter, in his "Historical Journal," gives no clear account of it; uncoloured.--ELIVI; from the manner in which the islets on the reefs are engraved, in the "Atlas of the 'Astrolabe's' Voyage," I should have thought they were above the ordinary height, but Admiral Lutke assures me this is not the case: they form a regular atoll; coloured blue.--GOUAP (EAP of Chamisso), is a high island with a reef (see chart in "Voyage of the 'Astrolabe'"), more than a mile distant in most parts from the shore, and two miles in one part. Captain D'Urville thinks that there would be anchorage ("Hydrog. Descript. 'Astrolabe' Voyage," page 436) for ships within the reef, if a passage could be found; coloured pale blue.--GOULOU, from the chart in the "'Astrolabe's' Atlas," appears to be an atoll. D'Urville ("Hydrog. Descript." page 437) speaks of the low islets on the reef; coloured dark blue.


Krusenstern speaks of some of the islands being mountainous; the reefs are distant from the shore, and there are spaces within them, and not opposite valleys, with from ten to fifteen fathoms. According to a MS. chart of the group by Lieutenant Elmer in the Admiralty, there is a large space within the reef with deepish water; although the high land does not hold a central position with respect to the reefs, as is generally the case, I have little doubt that the reefs of the Pelew Islands ought to be ranked with the barrier class, and I have coloured them pale blue. In Lieutenant Elmer's chart there is a horseshoe-formed shoal, laid down thirteen miles N.W. of Pelew, with fifteen fathoms within the reef, and some dry banks on it; coloured dark blue.--SPANISH, MARTIRES, SANSEROT, PULO ANNA and MARIERE Islands are not coloured, because I know nothing about them, excepting that according to Krusenstern, the second, third, and fourth mentioned, are low, placed on coral-reefs, and therefore, perhaps, contain lagoons; but Pulo Mariere is a little higher.


Charles Darwin

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