210 ART. 3. B. KOTJ : 



interior, and traversed with cracks which usually radiate from 

 deeper clefts of the interior. They are the juvenile lava half 

 consolidated within the vents, where they burst open and were 

 thrown up into the sky. 



There the outer portion is farther cooled down, while the in- 

 terior is vesiculated and expanded by relief of pressure, thereby 

 creating cracks in the glassy skin. The lapilli, abundantly 

 scattered about, seem to be mainly fragments of the inner portion, 

 rent, open through mutual collision of the bombs while flying in 

 the air. Tlieir pétrographie nature is hypersthene- andésite with 

 hyalopilitic texture. The brown glass of the groundmass swarms 

 with equal quantities of augite and feldspar microlites. 



Microscopically, the rock is exactly the same as that of the 

 lapilli, except the textare, it is therefore not necessary to restate 

 here a pétrographie description (p. 211). The following points are, 

 however, wortliy of note : 



a) The flowage texture of dopatic hyalopilitic groundmass 



has no relation to the surface of bombs. 

 h) (Quantitative relation and the distribution of phenocrysts 

 are uniform throughout the mass. 



c) Microlithic bodies are quantitatively uniformly distributed 

 in different portions, contrary to expectation. 



d) All the pétrographie elements were already there during 

 the aerial journey, the crystallinity of bombs having already 

 been attained during their intercrateral stage. 



e) The only special aspect to be noted is the vesiculation of 

 the groundmass, wMch causes macroscopic differences in 

 color, texture and lustre. 



./') Yesicula3 during their formation shifted microlites away 

 sidewards. 



