THE ARCHAEAN FORMATION OF THE ABUKUMA PLATEAU. 267 



hornblende, detached from the larger crystals are, however, plentiful 

 in the apparently homogeneous feldspar. 



g) Finally, we come to the uppermost of the rock-series, now under 

 consideration, which is found along the banks of the Sameo-awa, at 

 the village of Odaira lying close by Negishi, not far fi-om the Iwundary 

 of the tertiary terrain under which the rock gradually dips to be seen 

 no more in this region. This rock represents the extreme phase of 

 development of the thick series of Gozaisho, the corresponding other 

 extreme is, as has been already stated, the one found near the west end 

 of the Gozaisho Narrows, just at the district-boundary of Kikuta and 

 Higashi-Shirakawa, and which I have already proposed to call the 

 feldspatJwse hornblende -schist. The present rock appears at first sight as 

 if it were made up of silt, ashes, and the paste of volcanic mud, con- 

 solidated and pressed subsequently to its present form. It is a rather 

 greyish, rudely fissile, slaty rock, simulating very much the appearance 

 of the clasto-amphibok slate of the Mihabu series^ which forms the base- 

 ment of the palaeozoic group of Japan. The present rock is glossy in 

 appearance on a cleaved face, and the greyish shade seems to l)e caused 

 by the light colour and aciculur habitus of actinolite, as well as by 

 the presence of minute grains of epidote, which make up no small por- 

 tion of the bulk of the rock. 



Under the microscope almost the entire rock is seen to be built 

 up of needles and fil^rous shred-like masses with a decided tendency 

 to parallel arrangement. Exceptional cases are not rare, as there 

 are often-times found confused aggregates of fibrous matter, concealed 

 by chloritic membranes, having an appearance very much like the 

 antigorite-variety of serpentines, especially when viewed between 

 crossed niçois. The actinolite is of a light-greenish colour and weakly 



1 B. Koto ; " On the so-called Crystalline Schists of Chichibu," in which the minute struc- 

 ture of the amphibole slate has been considered in full detail. This Journal, Vol. II, p. 112. 



