ON CORD1EKITE AS CONTACT MINERAL. 



315 



first noticed by the writer in the summer of 1887. By occasional 

 trips undertaken since then, the geological condition of the district 

 has been made out. the summary of which may here be sketched 

 as follows : — 



The Watarase- 

 gawa, ;i tributary of 

 Tone-gawa, takes its 

 origin behind Lake 

 Chiuzenji in Xikkô, 

 near the ( !opper mine 

 of Ashio in Shimo- 

 tsuke, and flows 

 south-westward for 

 about 35 kilometres, 

 along the strike-line 

 of the Palaeozoic 

 strata here develop- 

 ed, to the town of 



Omama in Ködsuke. 

 Here it leaves the mountainous region and makes a sudden turn 

 to S. E., entering the plain of Kwantö. An elliptical mass of Granite 

 makes its appearance along this river, beginning at the village of 

 Karafuro near Ashio, and ending near the village of Gödo in 

 Ködsuke, extending nearly 11 Worn, from X. to S, and 5 kilom. 

 from E. to W. The southern extremity of this granitic mass 

 gradually tapers and merges itself under the thick Palaeozoic layer, 

 granitic exposures appearing here only in the river-bed; while the 

 bordering ridges are composed of sedimentary rocks, which are 



Grunitt Cordicrib 



Sl.it, . 



Spatted Boundary qf th.- 

 Statt ■ Provinces . 



