202 ART. 3. — B. KOTÔ: 



white flecks in Fig. 5) and minute fragmentary plagioclase. The 

 whole microscopic aspect presents that of a tuff cemented with 

 glass. This feldspathic modification may be called the ' faience ' 

 of natural earthenware with fine semitranslucent texture. 



The fourth tijps (PI. XXII. Fig. 6).— It is marble- white and 

 fine, light and friable. It shows banding, caused by alternation of 

 a bluish compact zone (a) with a lustreless vesicular one {h). This 

 projectile is astonishingly rich in ill-defined granulated cordierite 

 (c in Fig. 6). The banding is, as seems to the writer, an in- 

 dication that the ejected fragment in question is not segregated 

 under plutonic conditions, nor a resorption-rest of an exotic 

 fragment, as it is usuaJly interpreted, but a primary segregation- 

 product of lavas near the surface. To support the writer's case 

 he has in his possession a liluish pumice full of cordierite, ejected 

 from Asama on December 14th, 1912. See PL XXI. Fig. 1. 



Microscopically, the [a) zone is exactly the same as the third, 

 lithoidal type, while the {h) zone represents the lava scum.^^ 

 Again, we have here an indication that the ceramicite and lava- 

 scum are genetically closely related. The banding points to being 

 a result of circulation of lava in the intercrateral area."^ 



The fifth type (PI. XXII. Fig. 7).— The wet-gray, striped, re- 

 sinous, porcelain-jaspilite variety, breaking with subconchoidal 

 fi^acture. 



The light colored stripe (a) is composed of subrectangular^^ or 

 roundish^-' crystals of cordierite (0.025 mm.) besides a few larger ones, 

 intermixed with prismoids of plagioclase and fine needles of hyper- 

 sthene ; the whole is imbedded in a colorless base, which encloses 



1) PI. XX. Fig. 6 shows the lava-scum zone (h) of the éjecta. 



2) F. A. Perret ; Amer. Jour. Sei, 1913, p. 3i5. 



3) See the photomicrograph, PI. XXII. Fig. 7 (groundmass). 



4) It is Lncroix's ' colloidal cordierite.' Op. cit. 



