THE GREAT ERUPTION OF SAKURA-JIMA IN 1914. 183 



although quantitatively insignificant. They never occur in euhedral 

 form, as we usually find them in basalts, and frequently constitute 

 nuclei of cumulophyric patches (Text-fig. 40, p. 178). Phenocrystic 

 pyroxenes are scarce and seriate, and deeply corroded, of wliich 

 subhedral hypers fchene generally dominates over anhedral augite, 

 although their proportions are sometimes reversed. Parallel growth 

 is often observed in larger pyroxenes. Magnetite occurs sporadi- 

 cally in clumps and crystals. All the phenocrysts are affected by 

 frequent shifting of the equilibrium of surroundings until the final 

 consolidation of the lavas has taken place. 



The groundmass of all specimens is very fine (PL XIX. Fig. 7, 

 PL XX. Fig. 4), brownish and hyalopilitic, being mainly built up 

 of dusted augite microlites mixed up with a subordinate quantity 

 of skeletal feldspar laths in a light-brownish globulitic base.^^ 



The submarine lavas of the eastern field (PL XX. Figs. 2-4) 

 were collected by the writer in April, 1914, at the lava-front at 

 Séto, and 2 specimens by F. Omoki in April, 1915, the latter being 

 from the raised heads of submarine flows now forming new rock- 

 islets off-shore. The pétrographie characters are the same as on the 

 aforementioned western side, excepting the presence of large olivine 

 (8 mm.) as in PL XX. Fig. 3. The external slaggy portion of 

 the lava- sheet is, however, wantinginolivine owing to gravita- 

 tive sinking of that mineral, and at the same time globulitic 

 colorless glass makes its appearance in the groundmass. 



In short, the submarine lavas also belong to the category of 

 the ohvine-bearing hypersthene-andesite, and are characterized firstly. 



1) H. S. Washington says, that the groundmass of the Italian submarine lavas is a clear or 

 sometimes brown glass thickly sprinkled with rusty brown or black dust, so much so as to be 

 almost or quite opaque in places. ' The Submarine Eruption of 1831 and 1891 near Pantellaria.' 

 Am. Jovr. Sei., XXVII. Feb., 1909. The globulitic or thickly dusted glass seems to be the imi- 

 versal characteristic of submarine lavas in the recent as well as in older ones in Sakiira-jima. 



