Changes of Level in the Pacific Ocean. 255 



south-east of Washington, is described by the same voyager 

 as lower than that island. The accounts give no evidence of 

 elevation. 



Christmas Island, still farther to the south-east, accord- 

 ing to the description of Cook, its discoverer, had the rim of 

 land in some parts three miles wide. He mentions narrow 

 ridges lying parallel with the sea-coast, which " must have 

 been thrown up by the sea, though it does not reach within 

 a mile of some of these places." The proof of a small ele- 

 vation is decided, but its amount cannot be determined from 

 the description. The account of F. D. Bennet (Geographi- 

 cal Jour., vii., 226), represents it as a low coral island. 



Jarvis Island, as seen from the Peacock, appeared to be 

 eighteen or twenty feet in height, which, if not exaggerated 

 by refraction (we think it not probable), would shew an ele- 

 vation of six or eight feet. This island is a sand flat, with 

 little vegetation, and is but two hundred miles south of 

 Christmas Island. 



Maiden, two hundred and fifty miles south-east of Jarvis, 

 near latitude 4° S., and longitude 155° W., visited by 

 Lord Byron, is described as not over forty feet high ; but 

 this may be the whole height, including the height of the 

 trees. 



e. Tonga Islands and others in their vicinity. 



All the islands of the Tonga Group about which there are 

 reefs, give evidence of elevation : Tongatabu and the Hapai 

 Islands consist solely of coral, and are elevated atolls. 



Eua, at the south extremity of the line, has an undulated, 

 mostly grassy surface, in some parts eight hundred feet in 

 height. Around the shores, as was seen by us from ship- 

 board, there is an elevated layer of coral-reef rock, twenty 

 feet thick, worn out into caverns, and with many spout-holes. 

 Between the southern shores and the highest part of the 

 island, we observed three distinct terraces. Coral is said to 

 occur at a height of three hundred feet. From the appear- 

 ance of the land, we judged that the interior was basaltic; 

 but nothing positive was ascertained with regard to it. 



Tongatabu (an island visited by us) lies near Eua, and is 

 in some parts fifty or sixty feet high, though in general but 



