The summit of the range, 2,000 feet in height, is “ridgy,” about half a mile in width, and cannot therefore be described as table-topped. The rocks exposed in blocks on the surface are composed of a semi-ophitic olivine-basalt containing a large amount of interstitial glass which shows the fibrous crystallites of the early stage devitrification. It is referred to genus 33 of the olivine-basalts.
Descending the northern side of the range I followed the steep slopes down to 1,000 feet above the sea. A rubbly doleritic olivine-basalt, semi-ophitic, and assigned to the same genus (33), prevailed on the way; and it is probable that a waterfall with a drop of 50 feet or more that is situated on these slopes indicates a large intrusive mass of this rock. During the rest of the descent to Vandrani, which lies in a valley at the foot of the range, and is elevated about 300 feet above the sea, basic agglomerates and palagonite-tuffs, together with deposits intermediate in character, were exposed at the surface. At times a semi-ophitic doleritic basalt similar to those displayed above, but without olivine, occurred in position. The blocks in the agglomerates are formed of a compact semi-vitreous basaltic rock, and are sometimes vesicular. At one place the palagonite-tuffs exhibited signs of alteration, being traversed by small fissures not over a third of an inch broad (5 to 8 mm.), and filled with a zeolite behaving like natrolite.
In some cliffs by the river at Vandrani are displayed fine and coarse non-calcareous palagonite-tuffs, bedded and dipping about 15° N. by W. They are penetrated by cracks, 5 mm. in breadth, which are filled with chalcedony. These tuffs are evidently in part derived from acid as well as from basic rocks, though mainly from the latter; and they show other alteration-characters. At the mouth of the Vandrani valley there are exposed in the river-bed coarse palagonite-tuff sandstones containing a little lime, and probably a few tests of foraminifera.
Reference may here be made to the mountain of Ravi-koro which, when seen from the north-east, rises up as a partially independent peak, with a broad base and a conical truncated summit, immediately west of the track followed in the descent from the summit of the range to Vandrani. It is probably not much under 2,000 feet in height, and exhibits bare precipitous cliff-faces on the north side. It would be worthy of the attention of the future investigator.