GEOLOGICAL OBSERVATIONS IN FIJI. 69 



the barrier relation on the northeastern and northwestern sides of 

 the ishmd, where it projects as two short horns. 



The writer's general impression is that the island has been elevated 

 quite recently. The fringing reef is regarded as a simple outgrowth 

 about the edge of tlie elevated island. The barrier reef at the north- 

 eastern and northwestern sides of the island may be connected with 

 subsidence connected with the down-faulting of the northern side. 



Group II. Islands Composed wholly of Limestone. 



Introduction. 



A considerable number of islands show outcrops of limestone only. 

 It is reasonable to suppose that in each case, volcanic rocks exist at 

 no great distance below the surface and have not been uplifted above 

 sea-level or, if so, have not been exposed by erosion. The presence 

 of sideritic veins cutting the limestones, veins probably deposited by 

 hot-spring action, tends to support this view. Kambara, the island 

 just described, lacks exposure of its volcanic basement, but its lime- 

 stone has been intruded by basalt; this relation is an exception to the 

 rule that most of the islands which show large masses of limestone 

 without an exposed volcanic substructure, have not been affected by 

 the later period of volcanism. 



What forms characterized the limestone masses before they were 

 uplifted? Were they atolls? This question will be discussed after 

 the facts concerning the islands, described by some as elevated atolls, 

 are stated. 



Wangava (Figure 31). 



Wangava is one of the least dismembered of all the limestone 

 islands visited. Naiau presents similarities in form, but this island 

 was only seen at a distance. 



The following sketch of Wangava (Figure 33) as seen from the 

 northern shore of Kambara, illustrates its flat aspect, visible from 

 practically any direction. The writer visited only the northwestern 

 side of the island. 



Wangava is 5 or 6 miles in diameter. It is surrounded by an 

 elevated rim with precipitous cliffs about the coast. Its interior is 



