566 CORAL FORMATIONS. April, 1836. 



best characterized of these, namely, the Maldive islands, ex- 

 tend in length for 480 miles, with an average breadth of sixty. 

 These atolls agree in most respects with the lagoons of the 

 Pacific; they differ, however, in several of them being 

 crowded together — such little groups being separated from 

 other groups by profoundly deep channels. Now if we look 

 in a chart, at the prolongation of the reef towards the northern 

 end of New Caledonia, and then complete the work of sub- 

 sidence, so as to continue producing the same results ; we 

 should have the original reef broken up into many patches ; 

 each of which, from the vigorous growth of coral on the out- 

 side, would have a constant tendency to assume a rounded 

 form. Every accidental break in the continuity of the first 

 line would determine a fresh circle. In the case, therefore, 

 of the Low or Dangerous Archipelago in the Pacific, I beheve 

 that the lagoon islands were moulded round the flanks of so 

 many distinct islands ; but in the Maldives, that one single 

 mountainous island, bordered by reefs, and very nearly of the 

 same actual figure and dimensions with New Caledonia, for- 

 merly occupied that part of the ocean. 



Lastly, to the extreme westward, the coast of Africa is 

 closely skirted by coral reefs, and according to facts stated in 

 Captain Owen's voyage, has probably been uplifted within a 

 recent period. The same remark applies to the northern 

 part of Madagascar, and, judging from the reefs likewise at 

 the Seychelles, situated on the submarine prolongation of 

 that great island. Between these two, N.N.E. and S.S.W. 

 lines of elevation, some lagoon and widely-encircled islands 

 indicate a band of subsidence. 



When we consider the absence both of M'idely-encircling 

 reefs and lagoon islands in the several archipelagoes and 

 wide areas, where there are proofs of elevations ; and on the 

 other hand the converse case of the absence of such proof 

 where reefs of those classes do occur; together with the juxta- 

 position of the different kinds produced by movements of 

 the same order, and the symmetry of the whole, I think it 

 will be difficult (even independently of the explanation it 



