XX 
CHANGES JN CORAL-REEFS 
505 
the lagoon-channel is remarkably deep, scarcely any alluvial 
soil has accumulated at the foot of the lofty included moun¬ 
tains, 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 of 
changes and disturbances in progress in the subterranean 
regions. 
It is evident, on our theory, that coasts merely fringed by 
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 upheaved. Now it is 
remarkable how generally it can be shown, by the presence 
of upraised organic remains, that the fringed islands have been 
elevated : and so far, this is indirect evidence in favour of our 
theory. I was particularly struck with this fact, when I found, 
to my surprise, that the descriptions given by MM. Quoy and 
Gaimard were applicable, not to reefs in general as implied 
by them, but only to those of the fringing-class ; my surprise, 
