MAKEMO. 107 



with ledges of similar material making out as points, or being isolated 

 boulders torn oft: the lagoon face and rolled into deeper water. 



Two additional gaps which we examined presented no distinctive features 

 from others we had seen, the cut through the beach rock leaving low walls 

 undercut at intervals, with sand bars across the gaps forming a more or less 

 wide opening from the lagoon side, till it butts against a mass of beach 

 rock boulders at the sea face of the gap. This mass of boulders is scattered 

 over a length of nearly a mile in a belt fully 400 to 450 feet wide, until it 

 reaches the base of the shingle beach. This shingle is often driven into the 

 shore belt of vegetation (PI. 64), and, thus becomes scattered and thrown 

 across the narrow land rim, and in heavy gales is rolled all the way into 

 the lagoon. 



At one point the shingle beach was perhaps not more than three feet high ; 

 the slope of the wide sea face on which the masses of boulders rested ex- 

 tended to within five feet of the outer edge of the reef flat ; the old ledge was 

 exposed for a width of from 50 to 100 feet inside of the raised Nullipore 

 edge. The sand beaches of the lagoon side often extend into the gaps and 

 form a series of parallel dams across the gaps where they are open to the 

 lagoon side. 



The face of the island of the land rim, opposite our anchorage, presents 

 a fine example of islands as buttresses at right angles to the trend of the 

 coast, for many of the gaps, not more than 50 to 100 feet apart, are only 

 separated by strips of low sand land from three to five feet high, ending at 

 the sea face, either into coral shingle beaches or into the wall of boulders 

 mentioned above. The reef flat is composed of old ledge, which also crops 

 out in the cuts below the beach rock stratum. 



The recent beach rock conglomerate is made up of masses of recent coral 

 fragments of all sizes (PL 65, fig. 2), from whole colonies to the merest chips, 

 and from similar fragments derived from the disintegration of the old ledge 

 rock, huge masses of which crop out through the beach rock conglomerate, 

 so that it is often difficult to determine whether a particular outcrop of old 

 ledge is a boulder, or a horse, still connected with the underlying old ledge. 



On going south the gaps of the land rim become less frequent. The 

 sand driven from the lagoon has only left low depressions between the 



