On Certain Areas of Elevation and Subsidence in 

 the Pacific and Indian Oceans, as deduced from 

 the Study of Coral Formations. — A Paper read 

 before the Geological Society on May 31st, 1837, by 

 Charles Darwin, F.G.S. 



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{Abstract, reprinted '/rem the 11 Proceedings" vol. ii.pp. 552-554.) 



The author commenced by observing on some of the most 

 remarkable points in the structure of lagoon islands. He then 

 proceeded to show that the lamelliform corals, the only efficient 

 agents in forming a reef, do not grow at any great depths ; and 

 that beyond twelve fathoms the bottom generally consists of 

 calcareous sand, or of masses of dead coral rock. As long as 

 lagoon islands were considered tne only difficulty to be solved, 

 the belief that corals constructed their habitations (or speaking 

 more correctly, their skeletons) on the crests of submarine 

 craters, was both plausible and very ingenious ; although the 

 immense size, sinuous outline, and great number, must have 

 startled any one who adopted this theory. Mr. Darwin remarked 

 that a class of reefs which he calls " encircling" are quite, if not 

 more, extraordinary. These form a ring round mountainous 

 islands, at the distance of two and three miles from the shore; 

 rising on the outside from a profoundly deep ocean, and 

 separated from the land by a channel, frequently about 200 and 

 sometimes 300 feet deep. This structure as observed by Balbi 

 resembles a lagoon, or an atoll, surrounding another island. 

 In this case it is impossible, on account of the nature of the 

 central mass, to consider the reef as based on an external 

 crater, or on any accumulation of sediment ; for such reefs 

 encircle the submarine prolongation of islands, as well as the 

 islands themselves. Of this case New Caledonia presents an 

 extraordinary instance, the double line of reef extending 140 



