SUBSIDENCE IN PACIFIC CORAL REGIONS. 277 



d. That the subsidence gradually diminished southwest- 

 wardly from some point of greatest depression situated to the 

 northward and eastward, is apparent from the Feejee Group 

 alone. Its north-east portion (see chart), 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 

 mountain islands of great magnitude. Again, along the north 

 side of the A^anikoro Group, Salomon Islands, and New 

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



In view of this combination of evidence, we cannot doubt 

 that the subsidence increased from the south to the north- 

 Avard or north-eastward, and was greatest between the Navigator 

 and Hawaian 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. 



Haiuaian Range. — We observe that the western islands 

 in the Hawaian Range, beyond Bird Island, are atolls, and 

 all indicate a large 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 long period since they 

 began to grow, which is borne out by the features of Kauai 

 showing a long respite from volcanic action. We detect proof 

 of subsidence, but not of a large amount. Moreover, there 

 are no deep bays ; and besides, Kauai has a gently-sloping 

 coast plain of great extent, with a steep shore acclivity of one 

 to three hundred feet, all tending to prove the smallness of 

 the subsidence. We should, therefore, conclude that these 

 islands lie near the limits of the subsiding ^rea, and that 

 the change of level was greatest at the western extremity of 

 the range beyond Kauai. 



The coral subsidence of the western islands of the range 

 bear some evidence of having in recent times commenced a 

 new subsidence. They all have little dry land and vegetation 

 about the reefs. Brooks's Island^ in latitude 28^ 15' and lon- 

 gitude 177° 20' W.y eighteen miles in circumference, has on its 



