214 ^- i^öTö. 



rocks WC h;ive to mention as cliief varieties the tifanite-hiofite amphibo- 

 lite,, tifanite-salite ampliiholite, titanite-feldspar amphiholite, and lastly, 

 hiotite-amphihole gneiss. Those of the second category show the follow- 

 ing modifications, viz., i\\Q gneiss -mica sdiist, two-mica schist, garnet-biotite 

 schist, and also hornbleiide-biotite schist. The whole complex has been 

 variously faulted in parallel lines, giving rise to a so-called stair-case 

 structure ; at otlier times horizontal pressure seems to have produced a 

 compressed arch. Again, in one case at Otsuka, a mass of hornblende- 

 granite must have been squeezed along a fault-line, considerably disturb- 

 ing the adjacent rock on the east, while on the other side schists seem to 

 overlie conformably the granitic basis (Fig. 7, PI. XXIA). This 

 boss affords an excellent example of the schistosity of a granite. The 

 peripheral portion is highly gneissose in structure in conformation to 

 the surrounding rock, and little by little it gradually passes to a 

 iionnal granular variety at the centre. How such structure has 

 been brought about is not an easy question to answer. It may 

 perliaps be the result of a crushing during epigenetic movement of 

 rocks, or may have been produced, as Rej^er^ assumes, during up- 

 welling of a semi-fluid magma by constant pushes (Nachscliub), by 

 lateral compressions. 



The amphibolites and gneisses, lying to the east of the last- 

 mentioned irruptive mass, have acquired a specially great fissility, 

 cleaving easily into a papery slab ; and owing to its loose texture, the 

 rock falls into a bluish-black, ashy-looking powder on weathered surfaces. 



The structure of the Archsean belt at this part is undoubtedly a 

 very complicated one, as has been suggested in the foregoing 

 lines. The rocks are mostly brought to a vertical position, or dip at 

 angles rarely less than 80°, with the strike of X. 20° W. Considering 

 their present position as a result of pressure, the recurrence of 



1 loc. cit. 



