Changes of Level in the Pacific Ocean. 251 



dence of changes confined to particular islands or groups of 

 islands. While the former exemplify one of the grander 

 events in the earth's history, in which a large segment of the 

 globe was concerned, the latter exhibit its minor changes 

 over limited areas. The instances of these changes are so 

 numerous and so widely scattered, that they convince us of a 

 cessation in the previous general subsidence. 



The most convenient mode of reviewing the subject is to 

 state in order the facts relating to each group. 



a. Paumotu Archipelago. — The islands of this archipe- 

 lago appear in general to have that height which the ocean 

 may give to the materials. Nothing was detected which sa- 

 tisfied us of any general elevation in progress through the 

 archipelago. The large extent of wooded land shows only 

 that the islands have been long at their present level : and 

 on this point our own observations confirm those of Mr Dar- 

 win. There are examples of elevation in particular islands 

 however, some of which are of unusual interest. The in- 

 stances examined by the Expedition, were Honden (or Henu- 

 ake), Dean's Island (or Nairsa), Aurora (or Metia), and Cler- 

 mont Tonnerre. Beside these, Elizabeth Island has been 

 described by Beechey, and the same author mentions certain 

 facts relating to Ducie's Island and Osnaburgh, which afford 

 some suspicions of a rise. 



Honden or Dog Island. — This island is wooded on its 

 different sides, and has a shallow lagoon. The beach is eight 

 feet high and the land about eleven. There are three en- 

 trances to the lagoons, all of which were dry at low water, 

 and one only was filled at high water. Around the lagoon, 

 near the level of high tide, there were numerous shells of 

 Tridacna lying in cavities in the coral rock, precisely as they 

 occur alive on the shore reef. As these Tridacnas evidently 

 lived where the shells remain, and do not occur alive more 

 than six or eight inches, or a foot at the most, above low 

 tide, they prove, in connection with the other facts, an ele- 

 vation of twenty inches or two feet. 



Nairsa or Dean's Island. — The south side of Dean's 

 Island, the largest of the Paumotus, was coasted along by 

 the Peacock, and from the vessel we observed that the rim of 



