ON THE SO-CALLED CRYSTALLINE SCHISTS OF CHICHIBU. 99 



of the arrangement of the interpo.sition.s. The writer is, however, 

 inclined to view the .suhject from another stand-point ; namely, 

 that the clear periphery is due to an accretion of another generati<jn 

 resulting from the secondarij eiilaryiniient, the centre being the primary ; 

 the further point in regard to the cleavage, being perhaps explicable 

 as a result brought about by pressure induced afterwards. C. R. 

 van Hise^Mias lately found in the slate-conglomerates of the north 

 sliore of Lake Huron what may be enlarged felspar grains, but the 

 evidence there is not sufficiently satisfactory as to the material 

 being of secondary origin, the line of separation between the supposed 

 new material and the nuclei being indistinctly marked. The present 

 case affords better evidence of secondary enlargement, owing to 

 the circumstance that the new material on the clear periphery 

 being free of the above-mentioned interpositions is sharply marked 

 out from the core. 



The marginal portion of the fels[)ar nodides is fringed with, or 

 enclosed by a green sericite,-^ whidi is sometimes coloured brown 

 by the oxidation of iron contained in it : more especially after 

 ignition a slice of it acquires a deep Ijrownish-red colour, becoming 

 not unlike a common biotite, from which we may infer that our 

 green sericite is rich in ferrous oxide. This kind of mica seems 

 to be of a wide distribution in (metamorphic) schists outside the 

 Japanese Archipelago ; for the writer has observed the same in a mica- 

 schist from Killin, Perthshire, Scotland, and in all the ^ Amphilogit- 

 Schiefer^ from the Zillerthal in Tyrol. In petrographical literature 

 it has been described under various and even self-contradictory names, 



1) Bulletin TJ. S. Geological Survey, Vol. IT, p. 44. 



2) The present serioite miyjht probably be a modifiecl form of Phengite of Tschermak, 

 for it oontaias a large amount of Si Oj, but less of Ah Os, as may be seen from the numbers 

 stated in page 90. 



