When crossing the Natewa peninsula from Ndreke-ni-wai to the head of Fawn Harbour, one reaches a height of 660 feet above the sea. This ridge represents the “divide” between the Lea and Waikawa mountain-ranges. In the lower part of the northern slopes of this ridge occur basic tuffs and agglomerates; but between 200 and 400 feet a light-coloured acid rock of the hornblende-andesite type prevails, both in the form of agglomerate and of loose blocks. This rock is described under the second order of the hornblende-hypersthene andesites on page 299.
Descending the south slope, I found at an elevation of 500 feet a single large mass, about 4 feet across, of quite another type of volcanic rock, which is referred to the orthophyric order of the hypersthene-augite andesites (page 290). It is a dark grey almost holo-crystalline rock (sp. gr. 2·69) showing porphyritic pyroxene to the eye and displaying in its relatively scanty groundmass short stout felspars, ·05 mm. in length. On the surface of the lower two-thirds of this southern slope occur basic tuffs and agglomerates, basaltic blocks being found in the streams. The tuffs are palagonitic and contain a few calcareous particles. They apparently contain some foraminiferous shells and are doubtless of submarine origin.
It would seem that the axis or deeper portion of this ridge is composed of the hornblende and hypersthene-augite andesites, whilst the basic tuffs and agglomerates form the slopes.
With reference to the south side of the Lea sub-district, it may be observed that whilst on the north side the mountains rise up close to the sea-border, here they are separated from the coast by a broad tract of lowland, where bedded pteropod and foraminiferous clay-rocks are exposed, dipping gently to the south-east. Usually between Fawn Harbour and Vunilangi Inlet the coast is margined by low cliffs of coral-limestone, showing the massive corals in position; but sometimes the deposits above noticed compose the low cliffs and even the islets close by.
THE WAIKAWA MOUNTAINS.—This range occupies nearly the whole area of the broad and elevated promontory that is only separated from Taviuni by the narrow straits of Somo-somo, which, however, have a minimum depth of 120 fathoms. These mountains extend to the vicinity of Mbutha Bay on one side and to near Fawn Harbour on the other. Several of the peaks reach to over 1,000 feet, the greatest height given in the Admiralty chart being 1,540 feet. The whole region has a very rugged aspect, the mountains rising up near the coast, whilst the surface is much cut up into ridges and valleys.