Cn. v. 
OF CORAL-REEFS. 
181 
face there are a few worn patches of conglomerate coral- 
rock of about the size of hovels ; and these Captain 
Moresby considers as being, without doubt, the last 
remnants of islets ; so that here an atoll has been con- 
verted into an atoll-formed reef. The inhabitants of 
the Maldiva Archipelago, as long ago as 1605, declared, 
‘ that the high tides and violent currents were always 
diminishing the number of the islands : ’ 1 and I have 
already shown, on the authority of Captain Moresby, that 
the work of destruction is still in progress ; but that on 
the other hand the first formation of some islets is 
known to the present inhabitants. In such cases, it 
would be exceedingly difficult to detect a gradual sub- 
sidence of the foundation on which these mutable 
structures rest. 
Some of the archipelagoes of low coral-islands are 
subject to earthquakes : Captain Moresby infornjs me 
that they are frequent, though not very strong, in the 
Chagos group, which occupies a central position in the 
Indian Ocean, and is far from any land not of coral 
formation. One of the islands in this group was 
formerly covered by a bed of mould, which disap- 
peared after an earthquake, and was believed by the 
residents to have been washed by the rain into the 
underlying fractured rock : the island was thus ren- 
dered unproductive. Chamisso 2 states that earth- 
1 See an extract from Pyrard’s Voyage in Captain Owen’s paper 
on the Maldiva Archipelago, in the Geographical Journal, vol. ii. 
p. 84. 
2 See Chamisso, in Kotzebue’s First Voyage, vol. iii. pp. 132 and 
136. 
