THE GEEAT ERUPTION OF SAKUKA-JIMA IN 1914. 197 



teristic component, the remaining ingredients being basic plagio- 

 clase and colorless glass, with a subordinate amount of hyper- 

 sthene.^^ There are gradual transitions frori the preceding gabbroid 

 éjecta (pp. 190-196) and lava scums (pp. 187-190) to the one 

 under question, and a sharp line of demarcation cannot be drawn 

 between them. The only difference is the presence of a charac- 

 teristic, magnésie, orthorhombic mineral — the cordierite, which varies 

 quantitatively within wide range. The more crystalline the mass, 

 the less the amount of the cordierite, which sustains reciprocal 

 proportion to basic plagioclase.^-' If obsidian is a natural glass, the 

 éjecta may fittingly be called natural earthemoare or ceramicite"'^ 

 with modifications corresponding to pottery, stoneware and por- 

 celain. Ceramic wares are characterized by the presence of quartz 

 and sillimanite, wliile the natural products contain cordierite and 

 plagioclase in lieu of the two minerals. 



The cordierite-bearing éjecta from Asama-yama are now well- 

 known through the work of Hussak.*^ Since then other occurrences 

 were added to the list from Gôro-yama near the city of Nagano 

 (Zenkôji),^^ Ganju-san and Komaga-také near by, on the west of the 

 city of Morioka,''^ and the Komaga-také of Hokkaido."^ Exactly 

 the same éjecta were shown the winter by Laceoix,*^^ who gave a 

 description of them. Mention may be made here of projectiles 



1) Fine needles of this mineral often apj^ear under the microscope like rutile. Cf. p. 189, 

 footnote. 



2) From the measurement of maximum symmetric extinction, oligoclase seems to be pre- 

 sent among phenocrystic round crystals. 



3) The writer ventures to give this 7ieio name to the multifarious cordierite-bearing éjecta. 

 See ante, p. 187, footnote (1). 



4) 'Ueber den Cordierit in vulkanischen Auswürflingen.' Sitzungsber. d. K.K, Akad. d. 

 Wiss. in Wien. Math.-Naturwiss. Klasse, 1883, LXXX^TI. S. 332. 



5) N. Yamasaki, Jour. Geol. Soc. Tokyo, Vol. II. p. 397. Ihid. Vol. IV. p. 35. (-Japanese) 



6) Found in the collection of the late Mr. Sakuiai, deposited in our Museum. 



7) Tak. Katô, ' Ueber die Kordieritführenden Einschlüsse in der Lava aus dem Vulkan 

 Komaga-také auf Hokkaido, Japan.' Jour. Geol. Soc. Tokyo, Vol. XIX. p. 27. 



8) ' La Montagne Pelée et ses éruptions.' 



