On the Piedmontite-rhyorite from Shinano. 



By 

 N. Yamasaki, Rigakushi. 



College of Science, Imperial University. 



With Plate VI. 



The occurrence of piedmontite in Japan is well-known, on account 

 of its presence as an essential ingredient of a crastalline schist in the 

 Sambagawa series, which is pretty widely developed throughout the 

 country.* But this mineral had not been met with in other rocks 

 within the confines of the Japanese islands, before I found it recently in 

 the rhyolite from Shinano, a province lying to the north-west of Tokyo. 



The north-eastern part of the Shinano highland consists chiefly 

 of the tertiary formation, through which penetrate various kinds of 

 effusive and dyke rocks. Among them, andésite plays the principal 

 rôle, while the others occur, here and there, in comparatively small 

 patches. On the eastern side of the Chikuma, the largest river in the 

 main island (Hondo), and near the well-known cocoon market, Ueda, 

 there is a small range nearly 12 kilometres long, rising about 

 1300 metres above sea-level. It runs north-south, or nearly paralled 

 to that river. The eastern flank of the range hangs over the Soehi 

 valley, through which a tributary of the Chikuma runs southwards. 

 The greater part of this range is built up of the younger tertiary 



* B. Koto, Some Occurrences of Piedmontite in Japan. Jour. Sei. Coll., Imp. Univ., Tokyo. 

 1837, vol. I. p. 303. 



