3i6 A NATURALIST IN THE PACIFIC ch. xxii 



lava-cliffs, of which the beach represents but a small part of the 

 result ; and there were the dribbling eruptions of the crater, from 

 which at intervals of only a few minutes masses of semi-molten lava 

 bounded down the steep slopes into the sea. 



Note on the general characters of the rocks of the basic 

 agglomerates. — In appearance the basic rocks forming the blocks 

 are often very similar. They are usually compact blackish with a 

 semi-vitreous aspect and display some plagioclase phenocrysts. 

 But to enumerate the types to which they belong would be to go 

 over much of the ground traversed in the classification of the 

 basic rocks, whether olivine basalts, basaltic andesites, ordinary 

 augite-andesites, or hypersthene-augite-andesites. The ground- 

 mass as a rule contains much smoky glass, but the hemi-crystalline 

 portions of it vary considerably in character. Whilst fine granular 

 augite prevails, semi-ophitic coarser augites are not uncommon, and 

 prismatic pyroxene, sometimes of the rhombic form, is represented 

 in the groundmass of the rocks composing the agglomerates of 

 Mount Thambeyu and of the Sokena Cliffs. In some localities, as 

 on the south-west slopes of the Korotini Range, rocks of the basic 

 pitchstone kind are predominant. 



