THE ATOLL OF MINIKOL 39 



In the centre of the reef the rock masses are all much eroded underneath by the 

 seas, which at high tide, breaking on either side, meet one another in the middle of the 

 reef to rush along and escape at its north point. This central pinnacled flat is about 

 80 yards broad, and in places a few coral masses lie, some perhaps thrown up by the sea, 

 but most eroded out of the conglomerate. Between the masses a few pits are found, from 

 which the water does not escape, and in these flourish colonies of Porites arenosa and 

 Psammocora plicata (or similar facies). The lagoon face against the passage is similar to 

 the seaward, but the terraced arrangement is less noticeable. The pinnacles are fewer and 

 smaller, and the breadth is only about 30 yards. The drop outside is more abrupt, the 

 reef ending in a cliff of 1^ to 3 fathoms against the passage. The surface is smooth, but 

 various larger foliaceous and calcareous algae {Halimeda, etc.) flourish ; neither nullipores, nor 

 corals are found even at the extreme edge. Round the end of the point the conditions 

 of the two sides merge into one another, but the terraces are broader; the outer is not 

 marked with pinnacles, and slopes gradually to the depths below. 



A series of large table-topped dead rocks are seen on the backwash of the breakers out- 

 side the cliff against the lagoon passage ; they extend up from the level of the central 

 conglomerate masses in a line to the point of the reef Owing to the heavy seas I never 

 succeeded in making good my footing on any of these, but they appeared to be pitted and 

 bare of all organic growth except a few, low, green algae. They are apparently being eroded 

 underneath, subsequently to topple over and to be completely removed in a similar manner 

 to the conglomerate masses of the shore. I cannot find any record of such bare masses 

 in the numerous accounts of coral reefs. In those, which I have seen, I can only compare 

 them to the table-topped, raised reefs in some of the Lau islands of the Fijies ; the erosion 

 of the latter, however, is mainly between tidal limits. They may be the tables of much 

 taller mushrooms, the stalks of which have given way, while the tables have not yet been 

 cut down by the sea to the regular level in this position. / am, however, rather inclined 

 to believe that they are djie to a broadening of the passage, and that they show the maximum 

 effects which can be produced by the combined current and breaker actions on the reef. A reef- 

 flat consists of buttresses and masses which by organic growth have become joined together. 

 The water has got behind some of these, and the present table-shape results. The force 

 of the waves would cause a rapid denudation of the consolidating sand, and the constant 

 change of the water, due to the currents of the pa.s.sage, an equally quick solution. The out- 

 rushing water, carrying a large amount of dirt of all sorts in suspension, would prevent any 

 organic growth, so that the former actions would be unimpeded. 



Between Kodi and Mou-Rambu points the reef is very similar to that eastwards of 

 the former. There is a steep, boulder-strewn beach, and below this a series of terraces — 

 usually three with a step of 1 foot to each — before the regular outward slope commences. 

 The pinnacles of conglomerate are sparser, but usually a well-defined row marks the outer 

 limit of all except the most seaward, which is never uncovered at any tide. The latter 

 terrace is not well defined, being a flat for a certain distance and then tailing off sea- 

 ward into the outer slope. Its inner part is completely covered with low, green algae, 

 which to seaward give place to large nuUipore areas with occasional colonies of Madrepora, 

 Pocillopora, Coeloria and Psammocora in the hollows. The inner terraces are to some extent 

 covered with green algae, but neither nullipores nor corals are found except very rarely in 



