Cii. V. 
OF CORAL-REEFS. 
145 
It is even probable that tlie Maldiva Archipelago 
originally existed as a barrier-reef of nearly the same 
dimensions as that of New Caledonia (Plate II. fig. 5) : 
for if we complete in imagination the subsidence of 
this great island, we may infer from the broken condi- 
tion of the northern portion of the reef, and from the 
almost entire absence of reefs on the eastern coast, that 
the present barrier, after repeated subsidences, would 
become, during its subsequent upward growth, separated 
into distinct portions ; and these portions would tend 
to assume an atoll-like structure, owing to the corals 
growing with vigour where freely exposed to the open 
sea. As some large islands have subsided to a certain 
amount and are partly encircled by barrier-reefs, so our 
theory makes it probable that there should be other 
large islands wholly submerged ; and these, as we can 
now see, w T ould be surmounted, not by one enormous 
atoll, but by several large ones like the atolls of the 
Maldiva group ; and these again, during long periods 
of subsidence, would sometimes become dissevered into 
smaller ones. In the Marshall and Caroline Archipela- 
goes, there are atolls standing close together which 
have an evident relationship in form ; and we may 
suppose that either two or more encircled islands ori- 
ginally stood close together and afforded bases for two 
or more atolls, or that one large atoll has been dis- 
severed. But from the position as well as the forms of 
three atolls in the Caroline Archipelago (the Namourrek 
and Elato groups), which are placed in an irregular 
circle, I am strongly inclined to believe that they owe 
