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452 DR. BUNDJIRO KOTO ON SOME JAPANESE ROCKS. 
cent. of silica. The external appearance is black, homogeneous, 
translucent at the edge, and it possesses a conchoidal fracture. The 
microporphyritic ingredients are plagioclase, augite, and magnetite, 
the latter in octahedra. The asymmetric felspar contains abundant 
air-cavities and brown glass-enclosures. The augite occurs in well- 
developed crystals, and .through the transparent glass-mass the 
crystallographic faces are distinctly visible. It occurs in the com- 
bination of 0 Pam, 0o P w+ Pa,P,0oP. The augite has a deep 
brown colour and is pleochroic and free from foreign interpositions. 
In the microscopic section many felsospherites are present, bordered 
at their circumference by an anisotropic colourless substance. The 
glass-mass contains microliths with sharply pointed terminations 
(augite?), and these denote a microfluctuation-structure in the 
glassy paste. 
APPENDIX. 
Pre-Tertiary Rocks. 
GRANITES, 
The granite from Kinpozan, in the province of Kai, is a finely 
granular and uniformly crystalline rock, and is the matrix of the 
newly discovered tetragonal mineral, reinite (FeWO,) of Fritsch. 
Vnder the microscope the felspar presents a fibrous or rather 
wrinkled appearance, although it is not so clear and distinet as in 
some granulites. The fibrous feature has been variously described 
by v. Lasaulx, Zirkel, Dathe, and Kalkowsky, and lately it has been 
very fully studied by Becke*. Under polarized light between 
crossed nicols the felspar mass is seen to contain an interposed 
substance, which in its optical behaviour differs from that of the 
enclosing felspar, and thus causes a peculiar aspect in the latter 
mineral, Looking more into details, this interposed felspar substance 
has the form of spindles which run parallel to each other. Under 
high powers, the lenticular bodies are seen to be traversed by many 
oblique fissures in the direction OP., and in these the maximum 
extinction is 18° with P/M, while in the enclosing felspar it is 6°. 
The extreme minuteness of the interposed substance does not 
allow an exact measurement, nevertheless the difference in the 
extinction-angles in the two felspars is beyond all doubt. - 
The basal section of the felspar mass presents, under polarized 
light, between crossed nicols, the so-called ‘‘ eozoonal structure ” 
caused by the difference in the index of refraction of the enclosing 
and interposed felspars. Where the basal’ sections of the chief mass 
could be examined, they were found to extinguish the light, as a 
rule, parallel to the edge P/M; but this is not always the case. 
Therefore whether the enclosing felspar be orthoclase or microcline 
yet remains to be solved. 
Taking into consideration the optical properties f and general 
* Tschermak’s ‘ Mittheilungen,’ iv. p. 107. 
+ Tschermak’s ‘ Mittheilungen, iii., M. Schuster, “ Ueber die Orientirung der 
Plagioclase.” 
