THE GEEAT ERUPTION OF SAKÜRA-JIMA IN 1914. 217 



southeast on the mainland in Prov. Osunii, where the so-called 

 Mesozoic slate occurs, intruded by a granite boss which bears a 

 low grade copper ore-deposit. As stated elsewhere, Kagoshima 

 Bay can be best explained by an assumption of meridional fault - 

 block depression (pp. 18-20), and the basement upon which Sakura- 

 jima rests should be identical in geologic composition to the 

 neighboring plateau-land. The Plateau Formation (p. 14) is com- 

 posed of a lapilli bed underlaid by marine tuffite and trachyandesite, 

 which in turn lies upon eroded edges of Mesozoics intruded by 

 granite. 



The first and second are represented among the éjecta by the 

 'éjecta of trass' (p. 214), and the first also by the so-called 

 sandstone (p. 216). In addition to these, our new find of granite 

 among the recent éjecta is of great significance in deciphering • the 

 composition of the foundation of the volcano. Anyway the frag- 

 ment was disrupted from the bottom at least 1,000 7?^. below^ and 

 without being assimilated in the lava bath, was conveyed to the 

 surface. 



The granite block, 10 cm. in size, is rounded on the edges by 

 corrosion, and colored slightly brown. It is dull white and friable 

 through fritting by hot magma, and has an impaired and faded 

 aspect. See PL XXIII. Fig. 1. The feldspars have lost their lustre 

 and the biotite is changed into a brick-red mass. The microscope 

 shows the biotite to be impregnated along the cleavage plane with 

 yellow crystals of sulpiride ore (pyrrhotite), and newly formed minute 

 muscovite-like flakes take the place of the original biotite, some- 

 times arranged divergently, intermixed with hematite, the fresh 

 substance being no more seen, and appearing black in Fig. 1. 



The quartz is milky-white. It is minutely cracked, as if 

 quenched, and filled with muscovite (?) flakes. Some portion is 



