38 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
23, 27) and islands lying in the neighborhood of the Koro Sea present 
very steep angles.’ This angle in places exceeds 30° or even 35°. 
The slope is generally littered with huge spheroids of andesite. The 
basalt forms a much more gentle slope, as may be seen by a traverse 
of Taviuni. Usually the basalt is in very inconsiderable quantity and 
appears to be of younger date than the andesite. 
Tue Recent AGE OF THE VOLCANIC PHENOMENA. 
There appear to have been two distinct flows, one of andesite, the 
other of basalt. Both appear to be very recent, even subsequent to the 
last upheaval at Lau. Wherever volcanic rock is found in the smaller 
islands of Fiji, whether that island be wholly volcanic or part volcanic 
and part limestone, the eruptive rock is disposed of in gradually sloping 
hills, with heaps of lava blocks scattered indiscriminately, or takes the 
form of streams of volcanic stones littering the beaches. 
At Mango, Thithia (Plates 15, 16,19), Vanua Mbalavu, and Yathata, 
cliffs of limestone exist forming inliers in flows of andesite lava. It 
would seem that a great stream of andesite descended from higher levels, 
parted near what is the inlier, and then swept over the cliff on either 
side, and became confluent again at its base, where the lava was by de- 
grees piled so high as to be nearly on a level with the top of the cliff, 
and so produced a steep embankment sloping in one direction back 
towards the base of the cliff inlier, and in the other direction towards. 
the general trend of the lava flow. The contour of the lava bank as it 
lies under the cliff suggests that of a viscous mass flowing round a large 
obstacle and grown stiff before it had completely enveloped the 
obstruction. 
In Mango huge sections of strata may be seen exposed in gullies that 
have cut through the lower parts of the hill slopes (Plate 2, Figs. 
2,3). These strata have a decided dip, and consist of andesite tufts 
with large angular blocks of limestone scattered through the rock mass. 
These blocks are as much as a ton in weight, and consist of coralline 
rock indistinguishable from the present reef mass. A similar phenomenon 
occurs in the 9-fathom lagoon to the south of Mango, where the tuff beds 
are similar to those before described (vide map of Mango, Plate 1). The 
volcanic agglomerate is therefore clearly newer than the raised reef Jime- 
stone, and is in turn capped in places by a flow of andesite lava. 
The shape of the island of Vanua Mbalavu has been determined by a 
1 See A. Agassiz, /. c., Plates 34, 46, 48, 50, 57, 58. 
