BY B. SAWYER AND E. C. ANDREWS. 95 



C. — The Caves of Lau. 



The Eastern, Windward, or Lau group lies some 150 miles east 

 of the main island of Fiji (Viti Levu). The islands are disposed 

 in a direction approximately meridional, and lie along the axis of 

 a submarine anticline. 



The group is about 300 miles in length, and is composed of 

 numerous small islands. Many of these are composed of raised 

 coral limestone. The elevation was not confined to one period, 

 but consisted of uplifts alternating with periods of stable 

 equilibrium, which latter are marked by "terraces" or horizontal 

 extensions seawards of the coral growths, from the older mass of 

 the island. So great has been the total uplift that the basal 

 rocks on which the coral growths flourished may be frequently 

 seen. 



These basal rocks consist of huge masses of bedded limestone 

 of moderate dip (15°-25°), differing altogether in lithological 

 characters from the ordinary coral reef limestone. 



Again volcanic mudstones form a common base, as also exceed- 

 ingly decomposed volcanic conglomerates containing gasteropod 

 shells allied to Trochus, Nerita, etc. 



Mango, one of the group, may be briefly described as being 

 typical of the raised limestone islands containing numerous 

 caverns. The island is about 4 miles in diameter. It is approxi- 

 mately circular, and presents to the sea at almost all points 

 precipices of raised coral limestone. These are 400 to 500 ft. in 

 height. In former times an unbroken ring of limestone encircled 

 the island, but its integrity has been destroyed by later volcanic 

 outbursts. The perpendicular faces at times are succeeded by 

 escarpments of about 45° slope, and appear to represent the 

 original seaward slope of the atoll, for a raised atoll it appears 

 to be, being hollow in the centre, after the similitude of volcanic 

 craters. 



Several traces of elevatory movements exist as more or less 

 imperfect " terraces " or platforms of limestone. This limestone 

 area is covered with great masses of vegetation. 



