OF THE DEPENDENT ISLES OF TAIWAN. 25 



anotLer, various structures may be brought about under vary- 

 ing conditions, and these we find in fact in my slides. 



As regards the forms of augite, it is sometimes idiomorphic, 

 bounded by faces x P co^ cc Px , x P, and Px , the first being well 

 developed, consequently the crystals become tabular ; at other 

 times granular, needle-shaped, in ophitic plate, and in partial 

 crystals. Prevailing colour is either violet or yellowish-brown. 

 It is to be expressedly remarked that the typical Basaltic augite 

 with a tinge of violet occurs only in the Pescadores, and in the 

 dykes of Basalt near Taihoku and Taikokan, in Formosa. My long 

 experience forced me to conclude that, in Japan proper, the 

 Basalt with the violet augite is confined to the northern Kiu- 

 shiu, and Chiu-goku, in Hondo, as far east as the provincial 

 boundary of Tajima and Tamba. The same type of Basalt is 

 also known to be wide-spread in Korea, Liau-tung, and Mongolia. 

 Thus the distribution of the Basalt ivith the violet titaniferous 

 augite marhs a definite area, being, so far as my knowledge goes, 

 confined to the inner side of the festoon islands and the adjoiîiing 

 continent in Eastern Asia, constituting the well-defined Ja'pan- 

 China petrographical iwovince. Larger crystals show a zonal 

 structure, coloured intensely on the periphery, and the hour- 

 glass structure occurs frequently with deeply- coloured, additive 

 cones in the prismatic zones, which have at the same time a 

 greater angle of extinction. Pleochroism is stronger in the 

 direction parallel to the c-axis. Polarization-colours are generally 

 weak in comparison to those of the Andesitic augite. Twins on 

 ooPö) have a suture, running just along the middle of the body 

 of the crystals. Crystals often form stellar aggregates ; they are 

 generally free from foreign interpositions, excepting the larger 

 ones which have sometimes enclosures of glass and magnetite. 



