SUBSIDENCE IN PACIFIC CORAL REGIONS. 323 



miles. It is probable, therefore, that the subsidence indicated 

 was greatest at some distance north of the boundary line, 

 over the region of small equatorial islands, between the me- 

 ridians of 150° W. and 180°. 



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 those farther south, there 

 is over a region north of these islands, that is, between them 

 and the Hawaian Group, a wide blank of ocean without an 

 island, which is nearly twenty degrees in breadth. This area 

 lies between the Hawaian, the Fanning and the Marshall 

 Islands, and stretches off between the first and last of these 

 groups, far to the northwest. 



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 further 

 continued, and caused the total disappearance of islands that 

 once existed over 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 northeast portion (see chart), consists of immense 

 barriers, with barely a single point of rock remaining of the 

 submerged land ; while in the west and southwest there are 

 mountain islands of great magnitude. Again, along the north 

 side of the Vanikoro Group, Salomon Islands, and New 

 Ireland, there are coral atolls, but scarcely one to the south. 



