RANGIROA. 51 



islands piled up behind the wall on the lagoon flat is very striking; the 

 dark ragged points, the spires, the columns, the buttresses and walls stand- 

 ing out prominently from the light background. Thundering upon the 

 outer shore platform fall the huge rollers, which break at the base of the 

 wall and spend themselves on the platform, or at high tide throw the water 

 flir over the top, or force it through the openings between the undercut 

 and honeycombed columns and spires of which the wall is made up. 



There is a strong current making towards the lagoon through the gaps 

 where the rollers force their way in, and also in the gaps between the islets 

 wherever there is a passage for the sea, which is driven by the trades against 

 the weather side of the atoll. Where there is no pass we found upon the 

 shore platform, which is furrowed into a diminutive barrier reef and its 

 lagoon, a similar current flowing westward in the direction of the pre- 

 vailing winds. The decomposition and disintegration of the great wall sup- 

 plies a certain amount of coarse sand which is thrown up on the top of the 

 great wall and tends to conceal it; in addition sand is supplied from the 

 lagoon side flat, to form the high sand beaches which extend beliind 

 the sea wall and form the ridges of the higher islands or islets, which rise to 

 a height of perhaps 18 feet, or else form the high and steep sand beaches of 

 the islands to the east of Funuarua ; on the face of these project here and 

 there buttresses of the wall, at the foot of which are piled up masses of old 

 reef rock torn from the outer raised edge of the shore platform and thrown 

 up at the base of the sand beach. 



To the eastward of the nucleus of islands and islets of which Funuarua is 

 the centre, we could see, as we steamed away, extending to the easternmost 

 point of the island, islands and islets similar apparently in all respects to 

 those we had examined. 



In comparing the desci'iption given by Dana of the great wall occupying 

 the southern face of Rangiroa with what we saw, it is impossible to make 

 them agree. Dana speaks of the absence of islands on this face. It does 

 not seem probable that there should have taken place in sixty years such 

 extensive changes as are suggested by the description of Dana. The natives 

 whom I questioned assert that the condition of things which we found was 

 practically what it has been with very minor changes. It is probable that 



