1 62 CORAL-REEFS. 



breakers. At the Society Archipelago, on the other hand, 

 where a slight tremor is only rarely felt, the shoaliness of the 

 lagoon-channels round some of the islands, the number of 

 islets formed on the reefs of others, and the broad belt of 

 low land at the foot of the mountains, indicate that, 

 although there must have been great subsidence to have 

 produced the barrier-reefs, there has since elapsed a long 

 stationary period. 1 



1 Mr. Couthouy states {Remarks, p. 44) that at Tahiti and Eimeo 

 the space between the reef and the shore has been nearly filled up by 

 the extension of those coral-reefs, which within most barrier-reefs 

 merely fringe the land. From this circumstance, he arrives at the 

 same conclusion as I have done, that the Society Islands since their 

 subsidence, have remained stationary during a long period ; but he 

 further believes that they have recently commenced rising, as well as 

 the whole area of the Low Archipelago. He does not give any 

 detailed proofs regarding the elevation of the Society Islands, but I 

 shall refer to this subject in another part of this chapter. Before 

 making some further comments, I may observe how satisfactory it is to 

 me, to find Mr. Couthouy affirming, that " having personally examined 

 a large number of coral-islands, and also residing eight months among 

 the volcanic class, having shore and partially encircling reefs, I may 

 be permitted to state that my own observations have impressed a 

 conviction of the correctness of the theory of Mr. Darwin." 



This gentleman believes, that subsequently to the subsidence by 

 which the atolls in the Low Archipelago were produced, the whole 

 area has been elevated to the amount of a few feet ; this would indeed 

 be a remarkable fact ; but as far as I am able to judge, the grounds of 

 his conclusion are not sufficiently strong. He states that he found in 

 almost every atoll which he visited, the shores of the lagoon raised 

 from eighteen to thirty inches above the sea-level, and containing 

 imbedded Tridacnae and corals standing as they grew ; some of the 

 corals were dead in their upper parts, but below a certain line they 

 continued to flourish. In the lagoons, also, he frequently met with 

 clusters cf Madrepore, w?th their extremities standing from one inch to 

 a foot above the surface of the water. Now, these appearances are 

 exactly what I should have expected, without any subsequent elevation 



