THE FIJIS 337 



This eroded substratum, slightly modified by the growth 

 of the crust of recent corals found upon it, is in the Fijis 

 composed either of volcanic material or of elevated lime- 

 stone, whose sea faces, following the ancient slope of the 

 land mass, represent its former extension. 



The islands of Fiji may be divided into three classes 

 — elevated limestone, partly elevated limestone and 

 partly volcanic, and volcanic. As a rule the volcanic and 

 limestone islands are easily distinguished at a glance, 

 the gradual slopes of the volcanic peaks contrasting 

 strongly with the flat-topped summits and precipitous 

 cliffs of the limestone islands. 



The limestone cliffs, many hundreds of feet in height, 

 plainly attest a great upheaval of the region ; while the 

 outlines of the islands, deeply furrowed by gorges and 

 valleys, the sharp and serrated ridges separating them, 

 the fantastic outlines of such peaks as those of Viti Levu 

 and Yanua Levu, and others, all attest the extensive 

 denudation and erosion that has been going on in the 

 group for a very considerable period of geological time. 



Since the volcanic islands would naturally be eroded 

 to a less extent than the limestone, it is not surprising 

 to find that the larger islands, like Kandavu, Taviuni, 

 and Ovalau, are of volcanic origin ; while some of the 

 limestone islands have been almost entirely eroded. So 

 that of many which once occupied the area of present 

 lagoons, like Ngele Levu, there is left only here and 

 there a small island to attest the former existence of the 

 more extensive elevated limestone, that once covered the 

 whole area of what is now an atoll. 



The elevated limestone islands, such as Maiau, Tuvutha, 

 and many others, with bluffs of coralliferous limestone, 

 have been by some considered as elevated fossil atolls 



