86 B. KOTO 



regular order, separated by bands of a homogeneous (but not amor- 

 plioiis) quartz. The S(3-formed rock has Ijeen then subjected to the 

 act of crushing l)y mountain -making, and that trituration, as it were, 

 must have been secondarily induced, may be proved from the discon- 

 tinuity of irregular fissnres which become very numerous on the upper 

 and l(3wer margins of the quartz-bands, but stop short at the centre. 

 These fissures are particularly numerous at the turning points of the 

 plicature of tlie rocks, and indeed, the quartz appears there perfectly 

 granular. 1) F. I'ecke has. in rocks of a similar nature, encountered 

 the quartz-grains arranged in a fan-shaped form ; this being shown by 

 the manner in which the extinction-direction of polarized light varies 

 as the grains are examined in succession around the radial centre. He 

 has rightly compared this phenomenon with that in the twisted smoky 

 quartz from the Kreutzlipass in Switzerland.^) This peculiar fact of 

 which the cause is apparently unknown to him may, as it seems to the 

 writer, be ascribed to the special circumstances under Avhich the rock 

 containing a homogeneous quartz has been granulated. R. Küch,^) 

 while studying the rocks from Mamanyamatali, Western Africa, seems 

 to have noticed a similar fact, and from this, he formed a hypothesis 

 regarding the clastic nature of the epidote-mica-schist, in which he saw 

 the structure. Some of these grains (apparent) may be a product 

 of secondary infiltrations, and they are distinguished from the rest by 

 weak polarization-colours. Such grains are generally free from inter- 

 positions and inclosures, whatever the kind may be, as this quartz is 

 the latest among the rock- components. Slow, insensible, undulatory 

 extinction of light invariably takes place in this variety. 



In a schist from Inatsuka, in the Sambagawa valley, we noticed 



1) Michel-Levy calls such quartz masses "Quartz granulitique." Bull. geol. (3) VII. 

 p. 846. 1879. 



2) Tschermak; Min. u. petr. Mitth. Band VI. 'Gesteine von Griechenland,' p. 6ti. 



3) ibid. Band VI, p. 102. 



