Couthouy on Coral Formations. 137 



Art. XL — REMARKS UPON CORAL FORMATIONS IN THE 

 PACIFIC ; WITH SUGGESTIONS AS TO THE CAUSES OF 

 THEIR ABSENCE IN THE SAME PARALLELS OF LATI- 

 TUDE ON THE COAST OF SOUTH AMERICA. By Joseph P. 

 Couthouy. Read December 15, 1841. 



[Continued from page 105.] 



The conclusions to which I have been led by all the ob- 

 servations made among the coral islands of Polynesia, may be 

 summed up as follows : — firstlyj that the subsidence was not 

 continuous, but interrupted by long periods during which the 

 land, and after its disappearance, the reef, remained stationary, 

 and the successive terraces were formed ; secondly, that it 

 cpntiiiived, at least in certain places, up to a comparatively 

 recent dav, and ceased not long after the total submergence of 

 the pre-^'asting land ; thirdly, that there followed an indefi- 

 nite in/erval of repose, with the reef at a sufiicient depth 

 below the surface of the ocean, to enable the polypes to con- 

 struct the overhanging shelf whose fragments now strew the 

 upper plateau ; fourthly, that to this quiescent state ensued 

 one of re-elevation,* at a period of which, when the shelf 

 was considerably lower than the plateau now is, yet exposed 

 to the full violence of the surf, it was torn off and the frag- 

 ments carried to their present locality ; and lastly, that this 

 re-elevatory process is still going forward, not only in the 

 coral groups, but also in most of the volcanic ones of Poly- 

 nesia. 



After what has been said, it is perhaps unnecessary to re- 

 mark further upon the first of these conclusions. As regards 

 the second, I will here briefly notice one of the facts on 

 which it rests. At Rose Island, a chain of coral reefs mostly 

 covered only at high tide, and small islets but a few feet 



• There is one peculiarity in the sea or barrier reefs of all the volcanic islandi, 

 for which, unless it is to be attributed to the recentness of their elevation, I 

 can at present suggest no explanation. I refer to the entire absence upon them, 

 no matter how exposed may be their situation, of any fragmentary ridges, such 

 as are found at every I'aumotu, even where the distance from '.he outer plateaa 

 to the lagoon ii much less than the breadth of some barrier reefs. 



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