244 James D. Dana, Esq., on 



c. When, after thus reducing the size of the atoll, the sub- 

 sidence continues its progress, or when it is too rapid for the 

 growing reef, it finally sinks the coral island, which, there- 

 fore, disappears from the ocean. Now it is a remarkable 

 fact that while the islands about the equator above alluded 

 to indicate greater subsidence than farther south, north of 

 these islands, that is, between them and the Hawaiian Group, 

 there is a wide blank of ocean without an island, which is 

 near twenty degrees in breadth. This area lies betweeen 

 the Hawaiian, the Fanning, and the Marshall Islands, and 

 stretches off between the first and last of those groups, far to 

 the north-west. 



Is it not, then, a legitimate conclusion that the subsidence 

 which was least to the south beyond the boundary line, and 

 increased northward, was still greater or more rapid over this 

 open area ; that the subsidence which reduced the size of the 

 islands about the equator to mere patches of reef, was farther 

 continued, and caused the total disappearance of islands that 

 once covered this part of the ocean \ 



d. That the subsidence gradually diminished south-west- 

 wardly from some point of greatest depression situated to the 

 northward and eastward, is apparent from the Feejee Group 

 alone. Its north-east portion, as the chart shews (see vol. 

 xiv.), consists of immense barriers, with barely a single point 

 of rock remaining of the submerged land ; while in the west 

 and south-west there are basaltic islands of great magnitude. 

 Again, along to the north side of the Vanikoro Group, the 

 Salomon Islands, and New Ireland, there are coral atolls, 

 though scarcely one to the south. 



In view of this combination of evidence, we cannot doubt 

 that the subsidence increased from the south to the northward 

 or north-eastward, and was greatest between the Samoan 

 and Hawaiian Islands near the centre of the area destitute 

 of islands, about longitude 170° to 175° W., and 8° to 10° N. 



But we may derive some additional knowledge respecting 

 this area of subsidence from other facts. 



Hawaiian Range. — We observe that the western islands 

 in the Hawaiian Range beyond Bird Island, are coral islands, 

 and all indicate some participation in this subsidence. To the 



