ON TUE SO-CALLED CliYöTALLINE SCHISTS OF CHICHIBU. 123 



the waters of the depression of Chichibu find then* exit in a narrow 

 channel of the Arakawa by Minano and Yorii. Both rivers run 

 across the Sanibagawan series, and no sooner do the rivers enter the 

 region, than they assume a meandering course, being directed against 

 the strike of this series. This district is devoid of forest, and attbrds 

 only poor soils. 



(k) Massive Rocks. 



Eruptive rocks within the Sambagawan terrane make their 

 appearance as dykes, or more frequently in the form of massive 

 exposures ; the boundary between this and the adjacent rocks has 

 become quite indistinct owing to subsequent changes in themselves 

 and also in their mode of occurrence ; still it is beyond all reasonable 

 doubt that the eruptive rocks came out after the formation of the 

 Sambagawan schists, as is clearly indicated by considerable tectonic 

 disturbances in the neighboring rocks. The above-mentioned erup- 

 tives are gahhros and gahhro-diorites, both have always an intimate 

 connection Avith serpentines. 



Of late, we are acquainted from various sources with the wide 

 distribution of gabbros and the like in our country, and ample 

 materials are ready at hand which can only be treated on another 

 occasion. In the present paper the writer gives the description, for 

 the sake of completeness, of those only which occur within the 

 district under question. 



The typical rock is the gahhro-diorite found along the Arakawa, 

 on the cliff of Kosaka (Kanasaki) near the (often-mentioned) Minano 

 village. It is a whitish-gray, hipidiomorphic-granular rock of 

 originally massive structure, but now become more or less imperfectly 

 schistose (" grobflaserige "). The grayish mass is speckled with 

 dark brownish, satiny [)atches (sometimes an inch or more in size) of a 



