RAKOIA. 97 



We find the same digitating channels worn into the sea face of the reef 

 platform, cutting the outer edge into knolls which are gradually undermined 

 at the sea face of the reef platform, and finally are broken off in large 

 masses ; these are thrown up on the ledge flat and broken up little by little, 

 according to their size and their more or less exposed position on the plat- 

 form, and also according to their composition of hard old ledge or of more 

 easily disintegrated beach rock or recent conglomerate. 



The entrance on the west side of Raroia is fully 1200 feet wide, a 

 strong tide rip running diagonally across the mouth of the passage according 

 to the stage of the tide. The passage is flanked by a high and steep shingle 

 beach on one side, while on the other there is a low, long coral sand spit. 

 The west side is raked by the wind, the sea following the shore ; while the 

 east side is butted by the wind and sea, which clear the reef flat of all loose 

 material ; as the platform passes into the lagoon and comes under the influ- 

 ence of the lagoon wind and sea following the shore, it is again covered by 

 islets and bars. Opposite the gap forming the entrance we could see on the 

 other side of the lagoon a few islands both to the north and south. 



South of the entrance the land rim is more continuous, less cut into 

 islands, with long stretches of shingle beaches, and with small boulders of 

 beach rock at the base of the beaches, with here and there larger masses. The 

 shingle beaches are steep, from six to seven feet high. A section, from the 

 outer sea face of the reef platform to the top of the sand or shingle beach, 

 shows a reef platform of old ledge from seventy to one hundred feet wide, 

 edged with a growth of Nullipores rising from one to three feet above the 

 outer level of the flat and running out in a digitate form. At the base of 

 the beach crops out a ledge of beach rock, which at one time must have cov- 

 ered the greater part of the old ledge flat, but which has been washed away, 

 and supplied as elsewhere the material for the beaches and the building up 

 of the seaward part of the land rim islands. 



The stretch fi'om the southwest point to the southeast point forms a 

 great bight, similar in all respects to the stretches to the north on the west 

 face of the atoll ; the whole seems one long continuous stretch of land 

 rim without gaps, with a high beach of coral shingle, and a beach rock ledge 

 at the foot of the beaches. 



7 



