338 "ALBATROSS" TROPICAL PACIFIC EXPEDITION. 



between the roots of the trees growing upon the islets. Between this 

 inner channel and the outer face of the mangrove belt innumerable islands 

 and islets are forming, reaching as far as the outer beach. As we come 

 upon the southeast corner of the island, where the outer reef flat 

 approaches, and even encroaches upon the mangrove belts, the roar of 

 the surf can be distinctly heard. From Cape Tupinier these intricate 

 channels open out into more or less wide bays, separated from the sea 

 only by the high dam of beach rock conglomerate, or of coral rock 

 thrown up as a long shingle beach, and extending north as far as Chabrol 

 Harbor (PI. 229). From Cape Tupinier the lagoon channel extends nearly 

 to Point Duperrey. The outer belt of mangroves is quite narrow, while 

 the inner belt is far less important than off the southern coast. The 

 western shore of Chabrol Hai'bor is again edged by mangrove islands. 



The island to the west of the channel leading into Port Lottin consists 

 of coral rock and shingle thrown up at least six feet above high-water mark. 

 A similar process took place upon the whole of the volcanic reef flat; as it 

 was cut away, the masses of limestone which form the various patches upon 

 which corals are now growing were thrown upon it from the then existing 

 sea face (PI. 187). Here and there volcnnic rocks jut out, and piles of 

 volcanic stones are to be seen cropping out in all directions. This shows 

 that below the patches of corals volcanic rocks exist, the outliers of which 

 indicate the process of planing off the great reef flat which has taken place 

 on the eastern, southern, and western faces of Kusaie (PI. 229). 



The islands off the entrance of Chabrol, and off other parts of the coast 

 of Kusaie, show how the barrier reef platform has been formed by denu- 

 dation and submarine erosion of the longer slopes and bluffs. From the 

 former have been cut the wider reef platform, as on the south coast, and 

 from the latter the narrow reef flats where there is barely room, some- 

 times, for a canoe to pass between the volcanic slopes and the coral 

 shingle dam forming the bari'ier reef. Where the barrier reef platform 

 is reduced to a minimiun, owing to the steepness of the slope of the 

 island, we pass at once from the narrow reef shelf to the volcanic rocks, 

 as on the eastern slope ; -where the pitch of the volcanic rocks is less steep, 

 a wider and extensive reef flat has been eroded. On this shelf, however, 



