CORAL-REEFS. 161 



are in progress. These facts, if not directly connected with 

 subsidence, as I believe they are, at least show how difficult 

 it would be to discover proofs of such movement by 

 ordinary means. At Keeling atoll, however, I have 

 described some appearances, which seem directly to show 

 that subsidence did take place there during the late earth- 

 quakes. Vanikoro, according to the Chevalier Dillon, 1 is 

 often violently shaken by earthquakes, and there, the 

 unusual depth of the channel between the shore and the 

 reef, — the almost entire absence of islets on the reef, — its 

 wall-like structure on the inner side, and the small quantity 

 of low alluvial land at the foot of the mountains, all seem 

 to show that this island has not remained long at its present 

 level, with the lagoon-channel subjected to the accumula- 

 tion of sediment, and the reef to the wear and tear of the 



1 See Capt. Dillon's Voyage in search of La Peyrouse. M. Cordier, 

 in his Report on the Voyage of the Astrolabe (p. cxi. vol. i. ), speaking 

 of Vanikoro, says the shores are surrounded by reefs of madrepore, 

 " qu' 'on assure etre de formation tout-a-fait moderne." I have in vain 

 endeavoured to learn some further particulars about this remarkable 

 passage. I may here add, that according to our theory, the island 

 of Pouynipete (Plate I., Fig. 3), in the Caroline Archipelago, being 

 encircled by a barrier-reef, must have subsided. In the New S. Wales 

 Lit. Advert., Feb. 1835 (which I have seen through the favour of Dr. 

 Lloghtsky), there is an account of this island (subsequently confirmed 

 by Mr. Campbell), in which it is said, " At the N.E. end, at a place 

 called Tamen, there are ruins of a town, now only accessible by boats, 

 the waves reaching to the steps of the houses." Judging from this 

 passage, one would be tempted to conclude that the island must have 

 subsided, since these houses were built. I may, also, here append a 

 statement in Malte Brun (vol. ix. p. 775, given without any authority), 

 that the sea gains in an extraordinary manner on the coast of Cochin 

 China, which lies in front and near the subsiding coral-reefs in the 

 China Sea: as the coast is granitic, and not alluvial, it is scarcely 

 possible that the encroachment of the sea can be owing to the washing 

 away of the land ; and if so, it must be due to subsidence. 



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