324 CORALS AND CORAL ISLANDS. 



In view of this combination of evidence, we cannot doubt 

 that the subsidence increased from the south to the north- 

 ward or northeastward, and was greatest between the Navi- 

 gator and Hawaian Islands, near the centre of the area des- 

 titute 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. 



Hawaian 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 east- 

 ward 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 sub- 

 sidence, 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 area, 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 lan-d and vegetation 

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

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

 north and east sides a compact coral wall of about five feet 

 elevation, which continues for four and a quarter miles, and then 

 becomes a line of detached rocks at tide level. This bare 



