RLE J 'A TIONS IN PA CIFIC CORA L REGIONS. 2S5 



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 archipelago ap- 

 pear in general to have that height which the ocean may give 

 to the materials. Nothing was detected indicating any geuei-al 

 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 the author's ob- 

 servations confirm those of Mr. Darwin. There are examples 

 of elevation in particular islands, however, some of which are 

 of unusual interest. The instances examined by the Expe- 

 dition are those of Honden Island (or Henuake), Dean's 

 Island (or Nairsa), Aurora (or Metia), and Clermont Tonnerre. 

 Besides 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. 



Hondcji Island or Henuake. — This island is wooded on its 

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

 feet high, and the land about twelve. There are three entrances 

 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 deserted shells of the 

 huge Tridacna, often a foot long, 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 elevation of at least two feet. 



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

 the largest of the Paumotu s, was coasted along by the Feacock, 

 one of the Sloops of War of the Wilkes Exploring Expedition, 

 and from the vessel we observed that the rim of land consisted 

 for miles of an even wall of coral rock, apparently six or eight 

 feet above high tide. This wall was broken into rude columns, 

 or excavated with arches and caverns ; in some places the sea 

 had carried it away from fifty to one hundred rods, and then 



