94 ON CORAL REEFS AND ISLANDS. 



a single island, which subsidence has separated by inundating the 

 low intermediate area. The singular reef of Whippey Harbor, 

 p. 83, is fully explained by the hypothesis. We may thus not 

 only trace out the general form of the land which once occupied 

 this large area, (at least 10,000 square miles,) but may detect 

 some of its prominent capes, as in Wakaia and Direction Island. 

 The present area is not far from 4,500 square miles. 



The whole Feejee Group, exclusive of coral islets, includes an 

 area of about 5.500 square miles of dry land ; while, at the period 

 when the coral commenced to grow, there was, at least, as the 

 facts show, 15,000 square miles of land, or nearly three times the 

 present extent of surface. 



B. Lagoons of Atolls. — We pass from these remarks on the 

 channels and seas within barrier reefs, to the consideration of the 

 seas or lagoons of coral atolls. The inference has probably been 

 already made by the reader, that the same subsidence which has 

 produced the distant barrier, if continued a step further, would 

 produce the lagoon island. Nanuku is actually a lagoon island, 

 with a single mountain peak still visible; and Nuku-Levu, north 

 of it, is a lagoon island, with the last peak submerged. This 

 mode of origin may evidently be true of all atolls ; for with the 

 exception of the points of high land in the inner waters, there is 

 no one essential character, distinguishing many of the Eastern 

 Feejee islands from the Carolines to the North. The Gambier 

 group, near the Paumotus, appears to have afforded the philo- 

 sophical mind of Mr. Darwin the first hint with regard to the 

 origin of the atoll ; the contrast, and, at the same time, the re- 

 semblance, was striking ; the conclusion was natural and most 

 happy. # As some interest is connected with the history of new 

 principles, and the illustration afforded is highly satisfactory, we 

 have given a sketch of the Gambier group, (fig. 4, p. 91.) The 

 very features of the coast, — the deep indentations, — are sufficient 

 evidence of subsidence to one who has studied the character of 

 the Pacific islands :f for these indentations correspond to valleys 

 or gorges formed by denudation, during a long period, while the 

 island stood above the sea. 



The manner in which a farther subsidence results in producing 

 the atoll, may be illustrated by fig. 5, p. 91. Yiewing V, as the 

 water line, the land is entirely submerged ; the barrier, b"", b"", 

 is an angular reef, enclosing a broad area of waters, or a lagoon, 



* Captain Beechey, in his voyage in the Pacific, implies this resemblance, when 

 he says of the Gambier group, which he surveyed, " It consists of five large islands 

 and several small ones, all situated in a lagoon formed by a reef of coral" — p. 120, 

 Amer. ed. Balbi, the geographer, as Mr. Darwin remarks, describes those barrier 

 reefs -which encircle islands of moderate size, by calling them atolls, with high lands 

 rising from their central expanse. — Darwin, op. cit., p. 41. 



•J- This subject is discussed in the chapter, on the author's Geological Report, on 

 the valleys of the Pacific islands. 



