Inlands and Coral Reefs of Fiji. 417 



but a part of a more general elevation, which perhaps took place in 

 late Tertiary times, and iu which the whole group was involved. 

 It is plain that there must have been most extensive denudation and 

 submarine erosion going on throughout the group for a very con- 

 siderable time, geologically speaking. The outlines of the islands, 

 deeply furrowed by gorges and valleys, the sharp or serrated ridge& 

 separating the valleys, the fantastic outlines of the peaks and chains 

 of Viti Levu, Vanua Levu, and Ovalau, all attest to the great work 

 of atmospheric agency which must have been going on for so long 

 a period. 



" The extent of the separation of the islands, islets, or isolated rocka 

 from the points or spurs of the larger islands also bears witness to 

 the great length of time during which submarine erosion and denu- 

 dation have been at work. 



" The platforms of submarine erosion constitute the characteristic 

 features of the islands of Fiji. A glance at the sketch map of Fiji 

 and at the detailed charts of different portions of the group cannot 

 fail to show how extensive this action has been. 



" Add to this the fact that we are in a region of a former powerful 

 and extensive volcanic activity, the traces of which can still be seen 

 in all directions, and which has undoubtedly played a great part in 

 the lifting of the island masses and their subsequent shaping to their 

 present outlines. From this evidence I am inclined to think that 

 the corals of to-day have actually played no part in the shaping of 

 the circular or irregular atolls scattered among the Fiji Islands ; that 

 they have had nothing to do in our time with the building up of the 

 substructure of the barrier reefs encircling either wholly or in part 

 some of the islands ; that their modifying influence has been entirely 

 limited in the present epoch to the formatiorx of fringing reefs ; and 

 that the recent corals living upon the outer margin of the reefs, 

 either of the atolls or of the barriers, form only a crust of very 

 moderate thickness upon the underlying base. This base may be 

 either the edge of a submarine flat, or of an eroded elevated lime- 

 stone, or of a similar substructure composed of volcanic rocks, the 

 nature of that base depending absolutely upon its character when 

 elevated in a former period to a greater height than it now has ; 

 denudation and erosion acting of course more rapidly upon the 

 elevated coralliferous limestones than upon those of a volcanic 

 character. It is therefore natural to find that the larger islands, like 

 Kandavu, Ovalau, and Taviuni, are of volcanic origin, while the 

 islands which once occupied the area of the lagoons of Ngele Levu, 

 Nanuku Reefs, Vanua Mbalavu, the Argo Reefs, the Oneata, Yangasa, 

 Aiwa, Ongea, and Vatu Leile clusters, were composed of elevated 

 coralliferous limestones. They have disappeared almost entirely, 

 leaving only here and there a small island to attest to the former 

 existence of a more extensive elevated limestone, once covering the 

 whole area of what is now an atoll. Smaller volcanic islands, like 

 Matuku, Moala, Ngau, Nairai, and Koro, also show the greater or 

 smaller extent to which each has been eroded after its elevation, 

 being least in Koro and Matuku, and somewhat more in Moala and 



DSCADE IV. VOL. TI. NO. IX. 27 



