280 B- KOTö. 



Xear Hfirimichi, south-east of Fiikashima, Kochibe has found 

 many dykes of a dark-green, fine-granular diabase in granite, contain- 

 ing grains of olivine. ' This may probably belong to the same class 

 of rocks as the present one. 



A similar dyke may be seen in a vertical cleft of about 2 m. 

 within a nodular hornblende-granite at the boundary of Nakagura 

 and Nakatani (L P in Profile F-F, PI. XXV). 



C. Dijhcs of Dionte-Porphyntes. 



There are many peculiar dyke-rocks whose mutual relation to 

 each other, and to the country rocks are but imperfectly known. 

 I can give here only a preliminary notice of them, deferring their 

 microscopic detail to another occasion. Their mineralogical com- 

 position and structural form seem to deviate so greatly from normal 

 chß'e rocks, that I feel comulerahle diffidence in placing them in any 

 of the known class of lamprophyres. The dyke materials show 

 great variations within narrow limits. From a compact, grey 

 hornstone-porphyry to a light-coloured, coarse crystalline diorite- 

 porphyrite, they vary through a number of intermediate forms. Some 

 of them appear dark and fine granular, others are aphanitic ; while 

 a third modification is medium-granular with black hornblende- 

 crystals porphyritically imbedded within the greyish general mass. 

 In short, thev seem to have nothino; in common to them, but in 

 reality they are otFsprings from a common stock under deceptive 

 appearances. 



1) The compact variety possesses the aspect of a hornstone-porphyry, 

 with sporadic crystals of feldspar as a porphyritic component ; 

 the general mass is grey, and is splintery with a conchoidal 



1 Harada, Die ^axxinischen Inseln, p. 76. 



