ORIGIN OF THE BARRIER REEF. 257 



rare occurrence. If such patches of submerged land existed, 

 the lagoon structure would still be as inexplicable as ever ; for 

 the growing reefs of the Pacific show that corals may flour- 

 ish alike over all parts of the bank, where not too deep. The 

 zoophyte can by no means be said to prefer the declivity to 

 the central plateau of the submarine bank ; on the contrary, 

 the part nearest the surface below low-tide level, abounds in 

 the largest species of corals. 



II. ORIGIN OP CHANNELS WITHIN BARRIERS. 



A study and comparison of the reefs of different kinds, — 

 fringing, barrier and atoll, — throughout the oceans, is the only 

 philosophical mode of arriving at any conclusion on this sub- 

 ject. This course Mr. Darwin has happily and successfully 

 pursued, and has arrived, as we have reason to believe, at the 

 true theory of barrier reefs and coral islands. It is satisfac- 

 tory, because it is a simple generalization of facts. The ex- 

 plorations of the author afforded him striking illustrations of 

 its truth ; and elucidate some points which were still deemed 

 obscure, establishing the theory, as he believes, on a firm basis 

 of evidence, and exhibiting its complete correspondence with 

 observation. 



The reader may turn again to the chart of the Feejee 

 Group, and glance successively at the islands Goro, Angau, 

 Nairai, Lakemba, Argo Reef, Exploring Isles, and Nanuku. 

 It will be observed that in Goro, the reef closely encircles the 

 land upon whose submarine shores it was built up. In the isl- 

 and next mentioned, the reef has the same character, but is 

 more distant from the shores, forming what has been termed a 

 barrier reef ; the name implying a difference in position, but 



none in mode of formation. In the last of the islands enumer- 

 17 



