136 "ALBATROSS" TROPICAL PACIFIC EXPEDITION. 



Mehetia has no reef flats ; Tetiaroa and Motu Iti are composed of low 

 coral sand islands thrown up on a wide barrier reef flat. In Motu Iti and 

 Tetiaroa the volcanic peaks have disappeared, leaving nothing but a shallow 

 platform, upon the outer edges of which sandy coral islets have been 

 thrown up. 



There is, however, one point in which the barrier reefs of the Society 

 Islands differ from those of Fiji. The barrier reefs in Fiji are generally 

 indicated merely by reef flats, upon which the sea breaks, and an occasional 

 rocky islet or negro-head ; only rarely do we find sand keys upon the barrier 

 reefs of the islands of Fiji. In the Society Islands, on the contrary, we 

 usually find the line of the barrier reefs well indicated by long lines of nar- 

 row islets thrown up on the reef platforms, exactly as they are in the Pau- 

 motus. These islands and islets are generally well wooded, and thus give a 

 very peculiar aspect to the barrier reef. In the case of Bora Bora, Maupiti, 

 and Aitutaki, we have a central volcanic peak of considerable height sur- 

 rounded by a wide lagoon, the sea edge of which is formed by a fringe of 

 wooded islets and islands forming a more than half-closed ring around the 

 central island, which, in Bora Bora and Maupiti, rise in slopes and nearly 

 vertical walls, the former to a height of nearly 2400 feet, the other to about 

 800 feet. 



Tahiti, Huaheine, Bora Bora, Maupiti, and Motu Iti form a series of 

 islands in which we can follow the steps which characterize the successive 

 stages of denudation and of marine erosion they represent. 



The Society Islands are divided into the Eastern and the Western groups, 

 called the Windward and the Leeward Islands ; Tahiti, Murea, Mehetia, 

 Tetiaroa and Tubuai Manu^ forming the Eastern or Windward Islands. 

 The Leeward group consist of Huaheine, Raiatea, Bora Bora, Maupiti, and 

 Motu Iti. 



Huaheine, the easternmost of the Leeward group, is about twenty miles 

 in circumference and, like Raiatea, divided into two islands by a deep cut 

 similar to those of Murea, of Maupiti, and of Bora Bora, only in this case the 

 cut extends across the island, leaving but a narrow isthmus covered at high 

 water, to connect the northern and southern parts of the island. Huaheine, 



' We did not visit Tubuai Manu. 



