118 Agassiz — Islands and Coral Reefs of the Fiji Groiq). 



islands which once occupied the area of the lagoons of JSTgele 

 Levu, of the Nanuku reef, of Vanua Mbalavu, of the Argo 

 reefs, of the Oneata, Yangasa, Aiwa, Ongea and Vatu Leile 

 clusters being elevated coral reefs, they have disappeared 

 almost entirely, leaving only here and there a small island to 

 attest to the former existence of the more extensive elevated 

 reef once covering the whole area of what is now an atoll. 

 Smaller volcanic islands like Matukn, Moala, Ngau, Nairai and 

 Koro also show the extent to which each island has been 

 eroded after its elevation. The erosion being least in Koro 

 and Matnkn, somewhat greater in Moala and E"gau and still 

 greater in Nairai. In such atolls enclosing volcanic islands 

 like Mbenga, Wakaya, Makongai, the erosion and denudation 

 have been still greater, these islands covering but a compara- 

 tively small part of the area once occupied by the island 

 originally covering the area of the lagoon. Denudation and 

 erosion have been still more active in the Ringgold islands, in 

 the Kimbobo cluster and in Korno, and it may have gone 

 so far as to leave no trace in an atoll to indicate either its 

 volcanic or coral (elevated reef) origin : the shape of the 

 atoll being entirely due to mechanical action and not being 

 connected in any way with the growth of the corals which 

 have been found afooting upon reef-flats formed by atmos- 

 pheric agencies or by the action of the sea. 



So that as far as we can judge from the case of the Fiji 

 islands, the shape of the atolls and of the barrier reefs is due 

 to .causes which have acted during a period preceding our 

 own. The islands of the whole group have been elevated, and 

 since their elevation have, like the northern part of Queens- 

 land, remained nearly stationary and exposed to great and 

 prolonged denudation and erosion, which has reduced the 

 islands to their present height ; the platforms upon which the 

 barrier-reef corals have grown being merely the flats left by 

 the denudation and erosion of a central island of greater size 

 than that now T left ; while the atolls are similar flats from the 

 interior of which the islands have been eroded and the lagoons 

 of which have been continually scoured by the action of the 

 sea, the incessant rollers pouring a huge mass of water into 

 the lagoon, which finds its way out through the passages lead- 

 ing into it. 



In the Fiji islands the atolls and islands, or islets, surrounded 

 in part or wholly by barrier reefs, have not been formed by 

 the subsidence and disappearance of this central island, as is 

 claimed by Dana and Darwin. The Fiji islands are not 

 situated, as was supposed, in an area of subsidence, but on the 

 contrary they are in an area of elevation, so that the theory of 

 Darwin and of Dana is not applicable to the islands and atolls 

 of the Fiji group. 



