546 J. G. H. GODFKEY ON THE GEOLOGY OF JAPAN. 



and-copper district of Ani (prov. Ugo), the rhyolite has become soft 

 by decomposition, and in consequence a number of thin veins can be 

 worked profitably. Propylite and andesite are of rare occurrence. 

 The first is the containing-rock of some of the gold-mines in the 

 province of Satsuma (Serigano) ; the latter is traversed by some in- 

 ferior copper-veins in the province of Tajima. 



6. Horimui or Coal-bearing group. — This group of rocks appears 

 to be best developed in the western part of Japan, and there in the 

 northern part of the island of Kiushiu. Coal-bearing beds of con- 

 siderable extent have also been disclosed on the eastern coast of the 

 main island ; but here the coals are decidedly of more recent age than 

 those of Kiushiu, which, according to their fossils, belong to the 

 Cretaceous period. 



The coals occurring on the eastern coast are lignite, often show- 

 ing the structure of wood ; but those found in the western part of 

 Japan approach in their character and appearance the real coal of 

 the Carboniferous formation. In the present state of our know- 

 ledge it is impossible even roughly to assign the area of this coal- 

 bearing formation in Japan; but it is certainly of considerable 

 extent ; the area of the principal coal-fields in the western part of 

 Japan has been estimated by me at about 270 square miles 

 (Plunkett's Report on the Mines of Japan, April 22nd, 1875, p. 7). 



7. Kamailcotan or Metamorphic group. — The rocks belonging to 

 this group appear to form the backbone of the various islands com- 

 posing Japan. They are distinctly stratified and usually have a very 

 steep dip of 60° and more ; and they are represented by clay-slate, 

 sometimes changing into talcose-slate,mica-schist|( chiefly in the island 

 of Shikoku), chloritic schist, serpentine, and crystalline limestone. 

 In some parts of the country a dark- coloured quartzite appears to 

 be bedded with the clay-slate. Owing to the absence of any distinct 

 fossils, the probable age of this group of rocks is yet unsettled. Von 

 Kichthofen considers them Devonian >or Silurian ; but up to the pre- 

 sent time no decided proof has been adduced in support of this view. 

 A trilobite belonging to the genus Asaphus was shown to me during 

 my travels in the northern part of Nippon ; but I did not succeed in 

 finding anywhere a similar specimen in situ. Intruded granite and 

 diorite occur frequently in connexion with the metamorphic rocks. 

 On the whole the metamorphic rocks are poor in useful minerals, al- 

 though some of the most important copper-lodes in the northern part of 

 Nippon continue their course undisturbed from the old volcanic rocks 

 into the adjoining metamorphic slates ; and in a few other localities 

 deposits of considerable importance appear to belong entirely to this 

 group of rocks. ^ At Handa (prov. Iwashiro) a large deposit of silver- 

 ore occurs in mica-schist close to its junction with granite; and in 

 the island of Shikoku a large and well-defined copper-lode is found 

 in clay-slate and mica-schist interstratified with serpentine and 

 quartzite. The magnetic iron-ore deposits of Heigori (prov. Eiku- 

 chu) are associated partly with felsite and felspathic porphyry, and 

 partly with dioritic rocks ; sometimes they even come into contact 

 with crystalline limestone. The mode of occurrence leads to the belief 



