(3) _The junction of the agglomerates and submarine tuffs._—This is well displayed at the Taloko Cave. Here the agglomerates lie conformably on the sedimentary tuffs; but the line of junction is sharply defined and the only evidence of transition is afforded by the great diminution in the size of the blocks of the agglomerates, which are 1 to 2 inches across. Immediately beneath the agglomerate is a layer 2½ centimetres thick of a rather coarse sedimentary palagonite-tuff having the composition of the deposits above described, but not effervescing with an acid, and showing no foraminiferous tests. The size of its “grain” is about a millimetre. This passes downward rather abruptly into a chocolate-coloured marl-like rock, a centimetre thick, which is formed of the same materials but in a clayey condition. Beneath this is the calcareous foraminiferous palagonite-tuff referred to in the first paragraph.
It is apparent that for some time before the agglomerates began to accumulate on the sea-bottom there had been a fairly uniform deposit of submarine tuffs, evidently in rather deep water. Then followed a period during which the finest mud was deposited which is represented by the thin layer of chocolate-coloured clay. This was succeeded by the deposition of coarser sedimentary tuffs forming a layer about an inch in thickness. Then commenced the accumulation of the agglomerates, of which the materials were at first small and afterwards larger in size.
(4) _The core or axis of volcanic rocks._—This is represented on the summit by masses, 2 to 5 feet across, of two kinds of hypersthene-augite andesite, which are referred to genus 1 of that sub-class. One is a compact grey rock (sp. gr. 2·72) carrying phenocrysts both of rhombic and monoclinic pyroxene, the former prevailing, and displaying a small amount of interstitial glass. It is magnetic and exhibits marked polarity, as noticed in Chapter XXVI. The other is a scoriaceous rock containing numerous round steam-pores, ranging up to 5 millimetres in diameter and generally filled with clear quartz-crystals and lined by chalcedony. It contains semi-opaque glass in abundance, and is apparently a semi-vitreous form of the rock just described. Both rocks are to some extent altered.... On the crest of a spur, 500 feet below the summit, is exposed in position an augite-andesite, assigned to genus 13, sub-genus 1, species B, of that sub-class. It is non-scoriaceous and exhibits a considerable amount of greenish alteration products. (Sp. gr. 2·79.)