THE GREAT ERUriTON OE SAKUR.V-JTMA IN 1014. 211 



(j) YcsiGuisci arc loss in number around larger vesicles. 

 h) .Vround the hollows, microlites are tangcntially ai'ranged 

 parallel to the margin, indicating that the lava still re- 

 mained in a semifluid state during the gaseous expansion. 

 /) The sudden relief of pressure is solely responsible for the 



evolution and coalescence of gas pores. 

 0) Recent Lapilli ('little stones').-/-/) Lapilh or pumiceous 

 blocks making a large Inilk of éjecta around the iccsteru vents are 

 externally rusty brown and internally fresli and ash-gray, dotted 

 with plagioclase crystals (2-3 mm.). The feldspar shows a (/laij 

 fracturai surface streaked with polysynthetic lamellar sutures, and 

 the gray color is due to botli brown glass- and granular en- 

 closures. Pleochroic hypersthene and dee\) greenish-brown augite 

 (hypersthene>augite) are mafic phenocrysts. Micronoritic patches 

 of hypersthene and bytownite, and gabbroic ones were noticed. 

 The pumiceous hyalopilitic groundmass is of hroicnish glass, in 

 which are scattered fibrillated augite-needles, like spicules in 

 sponges.^^ A subordinate quantity of feldspar- laths is intermixed 

 with augite. The brownish outer portion of lapilli contains a 

 globulitic body in the vesiculae through oxidation in contact with air. 

 ß) In contrast to the lapilli of western Sakura-jima mentioned 

 above, tliose which fell in the Ushiné coast of Osumi Province, 

 which were thrown up from the eastern vents, are of lighter 

 shade (PL XXIII. Fig. 5). The microscope reveals not a few' dis- 

 tinctive features. Augite is apparently lacking, and hyperstliene 

 represents tlie whole pyroxene."^ Plagioclase is more basic, iiighly 

 biréfringent and more distinctly zonal- structured. Brownisli an- 



1) It is analogous to the structure of the thread-lace scoria (p. 187, footnote 2). 



2) PI. XXIII. Fig. 6. Isolated by washing after crushing of the lapilli that fell on Tabé 

 in the l'shintî coast near the defunct strait of Séto. 



