142 THEORY OF THE FORMATION Ch. V. 



would then resemble Phaleedoo and Moluqne atolls, or 

 Mahlos Mahdoo and Horsburgh atolls (Plate II. fig. 4), 

 which are related to each other only in proximity and 

 position. Hence, on the theory of subsidence, the dis- 

 severment of large atolls which are exposed to strong 

 currents and which have imperfect margins, (for other- 

 wise their disseverment would be scarcely possible), is 

 far from being an improbable event ; and the several 

 stages, from a close connection to the entire isolation 

 of some of the atolls in the Maldiva Archipelago, are 

 readily explicable. 



It is even probable that the 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, 

 would 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 sub- 



