ANDREWS: LIMESTONES OF THE FIJI ISLANDS. 25 
Munia. — It is described most accurately by calling it “a miniature 
Ovalau.” The same rugged cliffs of andesite agglomerate occur on a 
smaller scale, the total height here being 1000 feet. 
Lakemba. — The mass of the island is composed of andesite hills, 
crowding thickly one upon the other and rising at the highest point to 
720 feet above high-water mark. The former state of the island is 
represented by a mere fringe of coralline limestone on the southwestern 
extension of the volcanic mass. The whole configuration of the older 
limestone has been altered, unless, indeed, Lakemba was at one time an 
extensive limestone island. A little bigger volcanic display, and not a 
vestige of the older limestone would have remained, except perhaps as 
blocks in andesite ash beds, as is the case with some of the Mango 
limestones. 
The great attraction of Lakemba is its cave, piercing the fragment of 
limestone that skirt the volcanic slopes. The white residents describe 
it as an immense tunnel, easy of examination, and running for about two 
miles through the hill. Measurements by myself reduce this great 
length to 500 yards. Even thus the statement is misleading, for the 
cave disappears in the hill, describes an are of a circle, and by so doing 
reappears round the corner of the same bluff that it started at. From 
entrance to exit is about 200 yards measured round the outside of the 
cliff, and the exit is 100 feet above the entrance. The cave is more 
easily explored than any I have visited, the floor being fairly smooth, 
wide, and of even slope. Generally the roof is about 50 feet above the 
floor. The walls, where clean, reveal the structure of a raised reef, 
composed of corals and fragments of mollusca. 
Lines of Beach Erosion. — These may be divided into two groups, the 
ancient and the modern lines of tidal wear. 
In the islands of the Lau Group, and confined almost exclusively to 
the limestone formations, the effects of recent beach erosion are very 
pronounced. When a group of islands, of which the hundred isles of 
Ngillangillah (Plates 22, 35) and Mba Vatu may be cited as illustra- 
tions, have their windward face overlooking a fairly deep lagoon or are 
placed directly opposite an opening like the N¢gillangillah Passage, 
we find small islands quite undermined by wave agency, while others 
project in mushroom form above the surface of the lagoon (Plate 35). 
On the windward side of the Ngillangillah Group the erosive action 
has extended as much as 8 to 10 feet vertically and into the cliff face 
from 14 to 15 feet.1 To the leeward this cutting into the cliff rarely 
1 See A. Agassiz, /. c., Plates 73, 74, 92, 93. 
