1836.J CHANGES IN CORAL REEFS. 467 



on all sides of the lagoon old cocoa-nut trees undermined 

 and falling ; and in one place the foundation posts of a 

 shed, which ihe inhabitants asserted had stood seven years 

 before just above high-water mark, but now was daily 

 washed by every tide : on inquiry I found that three 

 earthquakes, one of them severe, had been felt here 

 during the last ten years. At Vanikoro, the lagoon- 

 channel is remarkably deep, scarcely any alluvial soil has 

 accumulated at the foot of tlie lofty included mountains, 

 and remarkably few islets have been formed by the heaping 

 of fragments and sand on the wall-like barrier-reef; these 

 facts, and some analogous ones, led me to believe that 

 this island must lately have subsided and the reef grown 

 upwards : here again earthquakes are frequent and very 

 severe. In the Society Archipelago, on the other hand, 

 where the lagoon-channels are almost choked up, where 

 much low alluvial land has accumulated, and where in 

 some cases long islets have been formed on the barrier- 

 reefs — facts all showing that the islands have not very 

 lately subsided — only feeble shocks are most rarely felt. 

 In these coral formations, where the land and water seem 

 struggling for mastery, it must be ever difficult to decide 

 between the effects of a change In the set of the tides 

 and of' a slight subsidence: that many of these reefs and 

 atolls are subject to changes of some kind is certain ; on 

 some atolls the islets appear to have increased greatly 

 within a late period ; on others they have been partially 

 or wholly washed away. The inhabitants of parts of the 

 Maldiva Archipelago know the date of the first formation 

 of some islets ; In other parts, the corals are now 

 flourishing on water-washed reefs, where holes made for 

 graves attest the former existence of inhabited land. It 

 is difficult to believe in frequent changes in the tidal 

 currents of an open ocean ; whereas, we have in the 

 earthquakes recorded by the natives on some atolls, and 

 in the great fissures observed on other atolls, plain evidence 



changes and disturbances in progress in the subterrnnean 



;ions. 



It is evident, on our theory, that coasts merely fringed 



reefs cannot have subsided to any perceptible amount ; 

 and therefore they must, since the growth of their corals, 

 either have remained stationary or have been upheavfd. 

 Now it is remarkable how generally it can be shown, by 

 the presence of upraised organic remains, that the fringed 



