A49 DR. BUNDJIRO KOTO ON SOME JAPANESE ROCKS. 
- fills up clefts in the felspars, and has been introduced as an 
alteration-product of the augite, and not of the felspars ; that is to 
say, the epidote in decomposed felspars is of an authigeneous origin, 
but the viridite which generates the epidote is of an allothigeneous 
origin, in the sense of KE. Kalkowsky. 
The veridite to which I here refer is the chloritic or serpen- 
tingous product of a decomposition of augite. It is sea-green or 
greenish brown, and consists of a very fine fibrous substance, the 
fibres being arranged parallel to the chief axis of the augite; at 
times the fibres form radial bunches from different centres, aggrega- 
tions of which represent the pseudomorphs after augite. Viridite 
is very weakly pleochroic ‘and displays aggregate polarization. It 
is partly soluble in HCL. 
The ground-mass is mostly holocrystalline and microscopically 
phanerocrystalline. All the porphyritic ingredients recur in it, and 
this ground-mass is, indeed, a second and a different phase of the 
crystallization. 
Hence the rock assumes a porphyritic structure. The felspar- 
microliths are lath-shaped simple crystals, or twins, possessing a 
hyaline lustre. The direction of the maximum extinction of the 
twinned microliths makes a smaller angle by 3°-4° with reference 
to the twin lamelle, than that of the porphyritic specimens, and 
they are probably andesine or oligoclase. Optical verification is, 
however, very difficult on account of their minute size. These 
microlithic felspars of the ground-mass may differ in species from 
the porphyritic crystals, because the former (microliths) came into 
existence after the crystallization of the greater (porphyritic) felspar 
from a chemically different magma. Hopfner conjectures these to 
be a lime-soda felspar, and the porphyritic ones a soda-lime felspar. 
Augite occurs in the ground-mass as grains or microliths. 
Magnetite—The primary magnetite is mostly found in well- 
developed crystals, while the secondary magnetite occurs in grains 
or as irregular masses. A glassy basis is rare; when present it is 
colourless or brown, sometimes devitrified, and contains trichites 
of all possible forms. 
The ground-mass is of two kinds with reference to the genesis of 
the mineralogical components, the one of granitic, the other of 
diabasic structure; in the former the Mg-Fe-silicates crystallize 
out before the felspar component, in the latter the reverse is the 
case. In most cases, however, the structure of the ground-mass is 
of a granitic character. 
Structural Variety and Individual Descriptions of Augite-andesites. 
As I have already stated, the augite-andesites are obtained mostly 
from the Izu province, which lies south-east of the Fudji-San. This 
peninsula is a volcanic district, traversed from N.W. to S.E. by the 
Amagi range, the highest point being the Amagi itself (4700 metres 
above the level of the sea), a volcano with six plainly traceable 
craters, now dormant, the others having solfataras. The Omuroyama 
