190 ART. 3.— B. KOTÔ : 



effect of color by total reflection of penetrating rays of light. It 

 is worth while to note that pores of the size of 0.07 mm. have httle 

 effect on the microscopic appearance, while those of the minute 

 size of 0.02 to 0.03 mm. lend an allochromatic gray color to the 

 scmn. The minuteness of size, of course, contributes to the in- 

 crement of vacuoles in a given space. 



All the scums, including the white and gray types, contain 

 bluish cordierite in moderate quantity, sometimes filled with glo- 

 bules of pyrrhotite, which habitually forms the centre of radiating 

 air-pores (PI. XX. Fig. 7, PI. XXI. Fig. 1). They may, therefore, 

 appropriately be called cordierltiferous scums, and their systematic 

 position should be allotted to the ceramicite group. 



2) The Gabbroids as Ejecta (PL XX. Fig. 8, PI. XXL Figs. 2-5, 

 PI. XXII. Fig. 1). — The projectiles of the gabbroids of segi^egate 

 nature are found in 4 forms. The « type is an elliptical bomb of 

 about 10 cm., thinly coated with black slag. It is friable, easily to 

 be crushed between the fingers, and its fracturai surface has a white 

 saccharoidal appearance with vitreous lustre. The ß type is found 

 in the form of flat discs. The /' type is met with in angular frag- 

 ments in black compact andésite. It has a porcelain-like aspect 

 (ceramicite) and resembles closely the weU-known cordierite-bearing 

 éjecta of the volcanoes of Asama and I wate. Microscopic patches 

 — the o type with the composition and fabric of norite, are fre- 

 quently noticed in the recent lavas from both the western and 

 eastern vents. Lastly, the e type occurs in enclaves, having an 

 eucritic composition, which deserves the new naîne of micro- 

 allivalite. 



T/ie o. type—'^ microtimte (PI. XX. Fig. 8, PL XXL Fig. 2), is 

 seen under the microscope to l^e composed of polygonal crystals of 

 anorthite, closely fitted together as in contact texture, thereby 



