18 



FOYE. 



A few isolated islets of limestone, on the north, connect this point 

 with the larger island, Yasawa-i-lau, which is entirely composed of 

 limestone. It is about 700 feet high and is honeycombed with a net- 

 work of caves, many of which extend below sea-level and in which 

 the tide rises and falls. The adjoining sketch of the island was made 

 from the northern side of Nathula (Figure 6). 



YASAWA I lAU 





Figure 6. Yasawa-i-lau as seen from the Southwest. 



The southern end of Yasawa-i-lau is composed of a sandy limestone 

 similar to that composing the northern end of Xathula. Lenses of 

 andesitic waste are interbedded with a glomeratic limestone. These 

 beds are overlain by a more massive, coralliferous limestone, faulted 

 down against them (Figure 7). The nature of the andesitic material 



interbedded -wath the limestone 

 leads to the conclusion that vol- 

 canic activity was going on at the 

 time the limestone was deposited. 



Nanuia, a small island just north 

 of Yasawa-i-lau, is connected with 

 the latter by sand-bars which are 

 exposed at low tide. Various un- 

 der-cut islets of limestone dot the 

 lagoon between the islands and occur also along the south side of 

 Nanuia. Nanuia is a volcanic island made up of interbedded agglom- 

 erates and basalt flows. No contact between the limestone and the 

 basalt could be found, though the limestone of the islets was seen 

 within twenty feet of the volcanic rock. However, inasmuch as islands 

 of volcanic ash, deposited under sul)aerial conditions, are found very 

 close to Yasawa-i-lau with their bedding dipping towards the limestone 

 cliffs, and since the ontcrop of limestone at tlie northern end of Nathnla 



Figure 7. Fault at Southern 

 End of YasaAva-i-lau. 



