AGASSIZ: FIJI ISLANDS AND CORAL REEFS. 17 



CLASSIFICATION OF THE ISLANDS OF FIJI. 



It will greatly facilitate understainling the relations of the islands 

 and coral reefs of Fiji, if we follow in their description a classification 

 which will bring together islands and reefs of identical or similar geo- 

 logical structure. 



We may take at first such volcanic islands as Koro, Ngau, and pass 

 to the larger islands like Taviuni and Kandavu, finishing that class of 

 islands with descriptions of Mbengha, Komo, and the like. We will 

 take up next islands and reefs composed wholly of elevated coralliferous 

 limestones like Marambo, passing to such islands as Xamuka, Ongea, 

 Falanga, and to such reefs as Wailangilala and Ngele Levu. Next the 

 island groups in which we find both volcanic and coralliferous limestones, 

 such as Lakemba, Mothe, Vanua Mbalavu, Kimbombo, and the like, 

 the two large islands of Viti Levu and Vanua Levu being ti-eated sepa- 

 rately. This will be followed by an account of the islands and reefs we 

 did not examine, and finally by a sketch of the atolls, the geological 

 struct\ire of which could not be determined, and which might owe 

 their origin to banks of submarine erosion, derived either from volcanic 

 or fi'om elevated coralliferous limestone islands. 



Undoubtedly the islands of Fiji, whether of volcanic origin or of 

 limestone, would vavy greatly in the height to which they had been 

 elevated. Naturally, the volcanic islands would be denuded and eroded 

 to a less extent than the limestone islands, and the comparison of the 

 islands in Lau might give us some idea of the extent of this erosion 

 and denudation. The volcanic islands, consisting mainly of breccia, 

 are of course far more rapiidly eroded than if they consisted of compact 

 volcanic rocks. 



Of course some of the islands which have been named here as vol- 

 canic or as composed of tertiary limestones may prove on more extended 

 examination to be composite islands, and in the rapid visit made to some 

 of the islands we may not always have discerned their most character- 

 istic features. Yet in a general way steaming between the islands, one 

 cannot fail to be struck with the totally different aspect of the volcanic 

 islands and of the islands composed of elevated limestone. A mere 

 glance is sufficient to distinguish the rounded and gradual volcanic slopes 

 (Plates 46, 51, 57, 58) from the flat-topped summits and precipitous 

 cliffs characterizing the limestone islands (Plates 75, 76, 79, 86, 88, 90). 



Gardiner has, as we have, classified the islands of Fiji into elevated 

 limestone islands, into elevated limestone and partly volcanic, and into 



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