THE ARCH^AN FORMATION OF THE ABUKUMA PLATEAU. 261 



of both series, but the upper part of the present rocks becomes 

 rather compact, slaty, or thick-taliular ; 2) colour more greenish or 

 greyish ; 3) absence of titanite and salite, compensated for by the 

 presence of chlorite, epidote, magnetite, tourmaline, and sometimes 

 rutile ; 4) structure not granular, but linear or parallel and more 

 or less compact, the last character especially giving solidity to the 

 rocks, so that they withstand atmospheric action better ; 5) 

 macroscopically, the mineralogical components are scarcely recogniz- 

 able in the green slaty rocks ; 6) microscopically, the ingredients, 

 especially the hornl/;iende, are in parallel and linear alignment, 

 so that a slide made parallel to the schistose plane presents the 

 same side of the minerals, whereas in the rocks of the Takanuki 

 series basal and longitudinal sections of the component-crystals 

 are visible in the same slide, lying confusedly together ; 7) 

 hornblende mostly needle-shaped or prismatic in habitus, while 

 in the other, it is polysomatic or tabular, or broad if prismatic ; 

 8) colour of the hornblende light-green, and not intensely-green or 

 brown. 



The rocks comprehended under the present group vary greatly 

 as well in their external appearance as in their inward structure, to 

 such an extent that they do not allow of characterization in a few 

 words. They differ stratigraphically as well as petrographically in 

 mineralogical composition being accompanied by a change of structure. 

 From a highly crystalline, somewhat granular member bearing the 

 stamp of a genuine crystalline schist to a compact, green, slaty assem- 

 blage, they grade one into another imperceptibly without any marked 

 break. This may be traced advantageously in coming down eastward, 

 along the rapids of the Samegawa, from the plateau of Takanuki to the 

 boundary of tertiary hills, at the very junction of which stands the 

 small village of Kadôno (Profile C-D, PI. XXV.) 



