590 



FOEMATION OF COEAL EEEFS. 



[Ch. XLIX, 



minor rings are no less than three, and even five miles in 

 diameter, and some are situated in the midst of the princinal 

 lagoon ; bnt this happens only in cases where the sea 



can 



mar 



The rocks of 



Maldives 



com 



may 



in a loose state from the beach, and which is seen when 

 exposed for a few days to the air to become hardened. 

 The sandstone is sometimes observed to be an aggregate of 

 broken shells, corals, pieces of wood, and shells of the cocoa- 

 nnt.^ 



The Laccadive Islands run in the same Hne with the 

 Maldives, on the north, as do the islands of the Chagos 

 Archipelago, on the south ; 



submerofed mountains 



manner 



■7iot volcanic. — The circular 



Origin of the circular form— 

 and oval shape of so many reefs, each having a lagoon in the 

 centre, and being surrounded on all sides by a deep ocean, 

 naturally suggested the idea that they were nothing more 



submarine 



coral : and this theory I 

 editions of this work. 



my 



in the earlier 



Although I am now about to show 

 that it must be abandoned, it may still be instructive to point 

 out the grounds on which it was formerly embraced. In the 

 first place, it h|id been remarked that there were many active 

 volcanos in the coral region of the Pacific, and that in some 

 places, as in Gambler's group, rocks composed of porous lava 

 rise up in a lagoon bordered by a circular reef, just as the 



Kaimenis have m 



times 



of Santorin.f It was also observed that as in S. Shetland, 

 Barren Island, and others of volcanic origin, there is one 

 narrow breach in the walls of the outer cone by which ships 

 may enter a circular gulf, so in like manner there is often a 

 single deep passage leading into the lagoon of a coral island. 



the lagoon itself seeming to 



represent the hollow or 



gulf 



^ 



Captain Moresby on the Maldives, ii. p. 400. 



Journ. Koy. Geograph. Soc, toI. v. part 



t See above, p. 69. 



1 



i 



4 



i 



