214 AKT. 3. — B. KOTÔ : 



the lava bath is simply caustic and slight, showing that the tempera- 

 ture in the vents was far below 900^C. Augite-microlites, as w^ell as 

 phenocrysts, are hematitized rusty brown, and the coloi*less glass has 

 become granular. The alterations occur patcliwise near the contact. 



9) Ejecta of Trass or Ash- stone {Uai-ishi). PI. XXIII. Fig. 3. — 

 There are peculiar éjecta, though quantitatively insignificant, among 

 the projectiles in western Sakura-jima. They grade in color from 

 brick-red to brown and finally to gray, and are trass-like poly- 

 miktic in composition, being built up of fragments (4 mm. to 1 cm.) 

 of the black Mesozoic slate and black porphyritic augite-andesite, 

 whitish pumice and grayish hornblende-biotite-hypersthene andésite. 

 The agglomeratic mass is sometimes coated witli a black rind of 

 recent lavas (Text-fig. 46). The éjecta may be grouped into two 

 forms : 



«) Grayish halh of more than C cm. in diameter, without any 

 coating of black rind. The form is the result of frictional abrasion 

 of friable projectiles while flying in the air. The balls or pseudo- 

 bombs effervesce with acids. 



ß) Angular fragments of various sizes, sometime attaining the 

 considerable dimension of 1 rn., and in one or two instances making- 

 hollows in the ground by projectile impact. The fragments, oi' 

 rather blocks, are always coated partially with black rind as in 

 Text-fig. 4G, and non-effervescent with acids. The core in contact 

 with the rind is colored brick-red through oxidation, gradually 

 changing into brown and then gray. 



Under the microscope, the black vitreous white-spotted rind, 

 5 cm. thick, proves to be a vitro-pyroxene andésite (porphyritic 

 obsidian) with, the phenocrysts of plagioclase, hypersthene prisms 

 and augite grains (hypersthene >augite). The bulk of the rind is 

 made up of brown glass, which is crowded with skeletal microlites 



