OF THE DEPEXDEXT ISLES OF TAIWAN. o3 



teîtiary offshoots. This mode of growth, the octahedric dendrile, 

 so called by ^Eorozewies, is well known in petrographical 

 literatnre, sii'.ec the publication of Prof. Zirkel's^^ woik. On 

 the other hand, it is said that the dodecahedric dendrite, as is in 

 the present case, is formed out of the magma poor in iron- 

 oxides. 



B- Special Description of Individual Occurrences of Basalts. 



A. THE GRANULAR TYPE. 



{PL I, F'uj^. 1 and 2.) 



As seen by the naked eye, it is greyish-black and compact, 

 with the dots of olivine which is the only visible component 

 of the whole mass. This type is represented by two specimens 

 from Hôko, and one from Hakusha.-' Microscopically it is 

 holocrystalline with the smaller phenocryst of olivine, imbedded 

 in the still finer aggregate of the ground-mass. 



The fineness of the ground-mass, however, varies in different 

 specimens, and even in the same slide. Some portion of the 

 same slide is, therefore, extremely rich in idiomorphic angite 

 to the total exclusion of felspar and olivine, but with small 

 patches of brown glass. Were this portion independently devel- 

 oped, it Avould be fitly called the Äugitile {Fig, 2). It is the 

 local assemblage of augite within the rock, and that mineral es- 



I ) ' Die mikroskopische Beschaffenheit de'" Mineralien und Gesteine.' Leipzig, 1873, S. 244. 



2) Collected at Eyô-fcô-san (^^ÜJ); and, according to Mr. Saito, it appears in I. horizon, 



i. e., the uppermost slieet, consequently the youngest of all the lavas of the Hôko Group 



{Fl. r, fig. 1). 



