160 CORAL-REEFS. 



individual atolls are elongated in the same direction with 

 the group, in which they stand. The Chagos group is less 

 elongated than is usual with other groups, and the individual 

 atolls in it are likewise but little elongated ; this is strikingly 

 seen by comparing them with the neighbouring Maldiva 

 atolls. In the Marshall and Maldiva archipelagoes, the 

 atolls are ranged in two parallel lines, like the mountains in 

 a great double mountain-chain. Some of the atolls, in the 

 larger archipelagoes, stand so near to each other, and have 

 such an evident relationship in form, that they compose 

 little sub-groups : in the Caroline Archipelago, one such 

 sub-group consists of Pouynipete, a lofty island encircled by 

 a barrier-reef, and separated by a channel only four miles and 

 a half wide from Andeema atoll, with a second atoll a little 

 further off. In all these respects an examination of a series 

 of charts will show how perfectly groups of atolls resemble 

 groups of common islands. 



On the direct evidence of the blue spaces in the map having 

 subsided during the upward growth of the reefs so coloured, 

 and of the red spaces having remained stationary, or having 

 been upraised. — With respect to subsidence, I have shown 

 in the last chapter, that we cannot expect to obtain in 

 countries inhabited only by semi-civilised races, demon- 

 strative proofs of a movement, which invariably tends to 

 conceal its own evidence. But on the coral-islands 

 supposed to have been produced by subsidence, we have 

 proofs of changes in their external appearance — of a round 

 of decay and renovation — of the last vestiges of land on 

 some — of its first commencement on others : we hear of 

 storms desolating them to the astonishment of their 

 inhabitants : we know by the great fissures with which 

 some of them are traversed, and by the earthquakes felt 

 under others, that subterranean disturbances of some kind 



