I made the ascent of Mount Vungalei from the village of that name. The peak is also known as Ndrukau. Basic agglomerates were exposed all the way up to an elevation of about 2,000 feet, where a bed of a somewhat scoriaceous basaltic andesite was displayed, the upper 200 feet being inaccessible but of the same agglomerate. At a height of 300 feet was observed another layer of the same basaltic rock. These intercalated beds appeared to be lava-flows rather than horizontal dykes. The agglomerates become less coarse in the upper part of the mountain where they take the character of agglomerate-tuffs. The blocks are composed, like those in many other parts of the island, of a dark semi-vitreous basaltic andesite, but often scoriaceous. But the most remarkable features of these agglomerates are the indications of two distinct pauses in their deposition afforded by the occurrence at elevations of 900 and 1,700 feet of a single horizontal bed, two to three feet thick, of coarse palagonite-tuffs. Each bed is exposed at the foot of a tall cliff of agglomerate forming a line of escarpment along the mountain-side. The larger fragments making up these tuffs are usually from 2 to 3 millimetres in size; but the process of palagonitisation is not complete; and we find inclosed abundant angular pieces of a dark fresh tachylyte-glass, finely vesicular, and fusing readily in the ordinary spirit-lamp flame. The tuffs contain little or no lime and seemingly no organic remains. In the lowest bed I noticed a little water-worn gravel. Both beds pass gradually into the underlying agglomerate; but their upper limits are well defined and the agglomerate commences abruptly.
It is thus seen that in the formation of the agglomerates there were two pauses when they gradually gave place to deposits of fine detritus made up of a vesicular basic glass that has since been largely converted into palagonite. Then followed a sudden renewal of the agglomerate-producing process. We can scarcely doubt that the agglomerates, with their scoriaceous blocks, and the palagonite-tuffs are in the main the direct products of volcanic eruptions. The rival claim of marine denudation as the agency concerned can be mostly but not altogether excluded. The agglomerates and tuffs of Mount Vungalei cannot be distinguished from those so often described in the case of the great inland ranges of the other parts of the island, the submarine origin of which is frequently demonstrated by the inclosed organic remains. It would seem that in the instance of Vungalei these deposits took place around the shores of a volcanic mountain that rose above the sea. On page 315 it is pointed out that in Stromboli with its dribbling eruptions we have a good illustration of the manner in which such deposits could be formed.