J. 'G. H. GODFREY ON THE GEOLOGY OF JAPAN. 545 



«hyte, and pumice, form a great portion of the island of Nippon, but 

 are less predominant in the islands of Shikoku and Kiushiu. Large 

 and extensive accumulations of a decomposed trachytic rock, often 

 300 feet and more in thiekness, can be seen in the northern part of 

 Japan in the neighbourhood of Murioka. Almost all the volcanoes of 

 Japan are extinct ; but a few, like Asamoyama, emit continuously 

 a dense sulphurous smoke, and occasionally eject ashes and pumice. 

 Sometimes a sudden outburst is recorded of a supposed extinct 

 volcano, as happened in the beginning of last year with that situate 

 on Vries Island, close to Yokohama. The island of Nippon, and 

 chiefly the neighbourhood of Eusiyama, is subject to frequent earth- 

 quakes of more or less violence ; during the year 1876, a large tract 

 of beach was elevated sufficiently to become dry land and available 

 for cultivation in the Miyeken, the S.W. part of Nippon. 



Hot springs in close connexion with new voicanic rocks are very 

 numerous in Japan. Extensive deposits of sulphur are found upon 

 the craters of old extinct volcanoes. 



4. Toshibets group. — This group of roeks consists of alternating 

 layers of sandstone, clay, and conglomerate, and is largely repre- 

 sented in the provinces of Echigo and Shinano. These rocks con- 

 tain petroleum and fibrous lignite. The latter, however, is some- 

 times closely associated with black shining coal ; and therefore it 

 appears to be highly probable that this and the older Horimui, or 

 coal-bearing group, occasionally pass into each other. The fossils 

 found in the Toshibets group of rocks lead to the belief that they 

 belong to the Middle or Lower Tertiary formation. 



5. Old Volcanic Rocks. — A considerable portion of all the islands 

 belonging to Japan appears to be made up of this group of rocks. 

 They often appear distinctly bedded, and have then a gentle but 

 considerably varying dip. The rock of most frequent occurrence 

 is a trachytic porphyry or rhyolite. 



A rhyolite of a light-green colour, which consists of a very fine 

 compact but not vitreous felspathic matrix enclosing small grains 

 of oligoelase, and sometimes small fragments of the same rock, is 

 the rock which contains most of the valuable metalliferous deposits 

 in Japan. As a rule, close to the contact between the deposit and 

 the rhyolite, the latter is impregnated with numerous fine grains 

 and sometimes well-defined small crystals of yellow iron-pyrites. 



A dark-green variety of rhyolite, showing larger grains of oligo- 

 elase, quartz, and fragments of the same rock imbedded in a compact 

 felspathic matrix, is usually found barren of ore-bearing veins or 

 deposits. 



Numerous lodes and deposits containing gold, silver, copper, lead, 

 and blende are found in the rhyolitic formation, and in several in- 

 stances they are cut off by dykes of basalt or dolerite. As a general 

 rule these lodes or deposits are of rather limited extent ; but some 

 of them, as the quartz veins of Sado (prov. Sado), Ikuno (prov. 

 Tajima), and Innai (prov. Uzen), are of considerable size, continue 

 to great depths, and have proved productive for a considerable num- 

 ber of years. In some parts of Japan, as, for instance, in the lead- 



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