STRUCTURE OF CORAL ISLANDS. 163 



same extent Standing on the north shore of the Raraka la- 

 goon and looking southwest, nothing is seen but blue waters. 

 Far in the distance to the right, and also to the left, a few 

 faint dots are observed ; and as the eye sweeps around in 

 either direction, these dots gradually enlarge and pass into lines 

 of verdure, and finally, distinct groves near the observer. At 

 Dean's Island, another of the Paumotus, and at some of the 

 Carolines, the resemblance to the ocean is still more striking;. 

 The lagoon is in fact but a fragment of the ocean cut off by 

 more or less perfect walls of coral reef-rock ; and the reef is 

 here and there surmounted by verdure, forming a series of 

 islets. 



In many of the smaller coral islands, the lagoon has lost 

 its ocean character, and become a shallow lake, and the green 

 islets of the margin have coalesced in some instances into a 

 continuous line of foliage. Traces may perhaps be still de- 

 tected of the passage, or passages, over which the sea once com- 

 municated with the internal waters, though mostly concealed 

 by the trees and shrubbery which have spread around and 

 completed the belt of verdure. The coral island is now in its 

 most finished state ; the lake rests quietly within its circle of 

 palms, hardly ruffled by the storms that madden the sur- 

 rounding ocean. 



From the islands with small lagoons, there is every variety 

 in gradation down to those in which there is no trace of a la- 

 goon. These simple banks of coral are the smallest of coral 

 islands. In all the larger islands the windward side is the 

 highest ; and sometimes it is wooded and habitable through- 

 out when the leeward reef is bare. The entrances to the la- 

 goons are accordingly on the leeward side. 



A single group of islands, the Gilbert or Kingsmill, af- 

 fords good examples of the principal varieties. It is at once 



