Coral Reefs and Islands. 155 



Savaii, the largest island of the group, is a gently sloping 

 volcanic mountain, much like its namesake, Hawaii, in its 

 features, with lavas looking as if not long out of the fire. It 

 has a broad reef for only 6 or 7 miles of its east shore; else- 

 where, on the east and north-east sides, the reefs are fringing 

 or wanting ; and on the southern and western sides mostly 

 absent. No evidence of elevation, and nothing certain as to 

 subsidence, has been reported from the island. 



The large Feejee group bears abundant evidence of subsi- 

 dence in its very broad reef-grounds, barrier islands, and atolls. 

 Fringing-reefs, or barriers with very narrow channels, occur 

 about some of the islands of the group; but in view of the 

 facts that have been stated, these are useless as evidence 

 either way. 



Thus the conclusions as to the changes of level about these 

 large Pacific groups south of the equator are not far from 

 Darwin's, although fringing-reefs and the volcanic character 

 of the island are thrown out of consideration, and other con- 

 ditions exist of varied interpretation. 



But cases of actual elevation occur in the Central Pacific 

 about several smaller islands, as proved by elevated coral-reefs. 

 These occur in the Austral and Hervey Islands south and 

 south-east of Tahiti, and in the Tonga or Friendly Islands. 

 In none of these, however, thus far reported is the elevation 

 over 300 feet : and the amount varies greatly in adjoining 

 islands of the same group, some affording proof of no elevation. 

 Hence only local changes of level, not a general elevation, can 

 be inferred. 



To the north of the equator, at the Sandwich Islands some 

 elevated reefs occur; but the amount of elevation is small, and 

 is not general in the group. Moreover, the reefs are small, 

 where any occur; and the largest island of the chain, volcanic 

 Hawaii, the easternmost, is mostly without reefs, as well as 

 the larger of the westernmost islands, Kauai, which has partly 

 bold and indented shores. 



13. To give a more adequate view T of the changes of level, 

 or the evidences bearing on the subject, along the u limits " of 

 the central area of subsidence, I mention some additional facts. 

 Tahiti is the large eastern island of the Tahitian group. 

 To the ivestivard, the islands (1) decrease in size; (2) increase 

 greatly in relative breadth of reef-grounds; (3) become deeply 

 indented in shores, as explained; and (4) include an atoll, 

 Tubuai, as one of the last two of the chain. While the reef 

 of Tahiti proves comparatively little subsidence at that end of 

 the group, and its reefs and channels are extensive enough to 

 make the proof good, the other islands indicate, on the Dar- 



