THE GREAT ERUPTION OF SAKUEA-JIMA IN 1914. 121 



absence of olivine and the anliedral form of magnetite. Tlie glass 

 base is full of dust or a little brownish, and contains a few 

 microlites of both augite and plagioclase. The whole structure 

 appears not unlike a spongy mass with skeletons, enclosing 

 elongated pores of more than 0.3 mm. in diameter. 



As regards quantity, the lapilli from the eastern vents are far 

 more numerous than those from the western, chemically the former 

 are rather basic, the reason of which is the presence of a basic 

 mineral, olivine. 



Chemical Among cjccta after a volcanic activity the product 



Composition ^-^^^ j^^g j-^^^^^ usually subjcctcd to chcmical aualysos is 

 ash. So far as the writer is aware, no definite conclusions 

 have yet been drawn from numerous chemical treatments, owing 

 to the heterogeneous origin and composition as well as varying 

 proportions of mineralogical ingredients dependent upon the dis- 

 tance fi^om vents. In collecting samples fresh ash must be chosen 

 with mention of date and locality, which is usually neglected. 



A few specimens of analyses made of the recent Sakura-jima 

 ash are given below : 



