184 ABT. 3. — B. KOÏÔ : 



by coccolithic structure, secondly, by comparative idiomorphy of 

 plagioclase, thirdly, by the presence of large sporadic magnetite 

 clumps, and lastly, by the dusted augite microlites in the light- 

 hrownish glass of the gi'oundmass.^^ The olivine and hypersthene 

 have close paragenic relations ; when the former appears in 

 noticeable quantity the latter correspondingly increases in amount. 



d) Characteristics of the Western and Eastern Lavas. — All the 

 ' hve' lavas of Sakura-jima have the same characters, not only 

 macroscopically but also microscopically, in their black color, their 

 mineralogical composition, and also in their texture. The same 

 holds good generally for all the historic lavas of the island. As 

 efïusives are, in contrast to plutonics and hypabyssals, not easily 

 susceptible to magmatic differentiation, they naturally consolidate 

 into a uniform homogeneous mass. To find hidden, slight and 

 constant differences among the recent lavas is, therefore, not an 

 easy task. 



In the preceding, the writer has characterized (c) the sub- 

 marine lavas from both the terrigene- subaqueous and genuine sub- 

 marine origin and {a) the main land flows. Slight deviations in 

 habits and also in chemical constitution may i^erhaps be observed 

 in the lava streams of distal and proximal ends from vents. As 

 ' hve ' lavas, while crawling in their downward course, describe 

 comphcate comminglings and rotatory movements in a horizontal 

 as well as in a vertical sense like streams and glaciers, specific 

 differences, if any, in chemical and textural points cannot be easily 

 recognized. In the foUowing, some prominent features of the lavas 

 from the western and eastern vents will be griven in a brief form. 



In the bilateral eruptions of Sakura-jima, the eastern vent at 



1) See ante, 54 ami 176. 



