ON CHANGES OP LEVEL IN THE PACIFIC OCEAN. 127 



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 which satisfied 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 ob- 

 servations confirm those of Mr. Darwin. There are examples of 

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

 usual interest. The instances examined by the Expedition, were 

 Honden (or Henuake), Dean's Island (or Nairsa), Aurora (or Me- 

 tia), and Clermont Tonnerre. Beside these, Elizabeth Island has 

 been described by Beechey, and the same author mentions cer- 

 tain 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 differ- 

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

 high and the land about eleven. 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 shells of Tridacna lying in cavi- 

 ties in the coral rock, precisely as they occur alive on the shore 

 reef. As these Tridacnas evidently lived where the shells re- 

 main, 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 twenty inches or two feet. 



Nairsa or Dearts 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 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 ex- 

 cavated with arches and caverns ; in some places the sea had car- 

 ried it away from fifty to one hundred rods and then there followed 

 again a line of columns and walls, with occasional arches as be- 

 fore. The reef, formerly lying at the level of low tide, had been 

 raised above the sea, and subsequently had undergone degrada- 

 tion from the waves. The standing columns had some resem- 

 blance in certain parts to the masses seen here and there on the 

 shore platforms of other islands ; but the latter are only distantly 

 scattered masses, while on this island, for the greater part of the 

 course, there were long walls of neef-rock. The height moreover 

 was greater, and they occurred too on the leeward side of the 

 island, ranging along nearly its whole course. 



The elevation here indicated was at least six feet ; but it may 

 have been larger, as the observations were made from ship-board. 

 Thirty miles to the southward of Dean's Island, we came to 

 Metia, one of the most remarkable examples of elevation in the 

 Pacific. 



