396 PACIFIC OCEAN. 
cated was greatest at some distance north of the boundary line, over 
the region of small equatorial islands, between the meridian of 150° 
W. and 180°. 
c. When, after thus reducing the size of the atoll, the subsidence 
continues its progress, or when it is too rapid for the growing reef, it 
finally sinks the coral island, which, therefore, 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 between the Hawaiian, 
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 north- 
ward, 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 dis- 
appearance of islands that once existed over this part of the ocean? 
d. That the subsidence gradually diminished southwestwardly from 
some point of greatest depression situated to the northward and east- 
ward, is apparent from the Feejee Group alone. Its northeast por- 
tion, as the chart shows, consists of immense barriers, with barely a 
single point of rock remaining of the submerged land; while in the 
west and southwest 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, although 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 northeast- 
ward, 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. 
Hawatan Range-—We observe that the western islands in the 
Hawaiian range, beyond Bird Island, are coral islands, and all indi- 
cate some participation in this subsidence. ‘To the eastward in the 
range, Kauai and Oahu have only fringing reefs, yet in some places 
these reefs are half a mile to three-fourths in width. They indicate a 
