136 CORAL-REEFS. 



lagoons. This remark, I may add, applies to all coral- 

 reefs wherever found. The bason-formed reefs of the 

 Maldiva Archipelago may, in fact, be briefly described, 

 as small atolls formed during subsidence over the separate 

 portions of large and broken atolls, in the same manner 

 as these latter were formed over the barrier-reefs, which 

 encircled the islands of a large archipelago now wholly 

 submerged. 



Submerged and dead reefs. — In the second section of the 

 first chapter, I have shown that there are in the neighbour- 

 hood of atolls, some deeply submerged banks, with level 

 surfaces ; that there are others, less deeply but yet wholly 

 submerged, having all the characters of perfect atolls, but 

 consisting merely of dead coral-rock ; that there are barrier- 

 reefs and atolls with merely a portion of their reef, generally 

 on the leeward side, submerged; and that such portions 

 either retain their perfect outline, or they appear to be 

 quite effaced, their former place being marked only by a 

 bank, conforming in outline with that part of the reef which 

 remains perfect. These several cases are, I believe, inti- 

 mately related together, and can be explained by the 

 same means. There, perhaps, exist some submerged reefs, 

 covered with living coral and growing upwards, but to these 

 I do not here refer. 



As we see that in those parts of the ocean, where coral- 

 reefs are most abundant, one island is fringed and another 

 neighbouring one is not fringed ; as we see in the same 

 archipelago, that all the reefs are more perfect in one part 

 of it than in another, — for instance, in the southern half 

 compared with the northern half of the Maldiva Archi- 

 pelago, and likewise on the outer coasts compared with 

 the inner coasts of the atolls in this same group, which 

 are placed in a double row ; as we know that the existence 



