128 "^'ol- XLIII., Art. C. — S. ïsuboi : 



there are two branches in what is commonly called " the Fuji 

 volcanic chain " — one comprising the volcanoes of basic rocks as 

 Oshima, Miyakejima, Hakone^\ etc. and the other including those 

 of the acidic rocks as Niijima, Kôzushima'\ etc. having a close 

 relation to the dacitic volcanoes of the Idzu peninsula ; and that 

 the recent activity of some of the former is known, while of 

 the latter there are, according to liim, no historic records of 

 eruptions. 



Later, in 1902, FuKucnf^ gave a fuller account on the distinc- 

 tion between these' two groups of insular volcanoes. He con- 

 sidered that the basaltic islands belong to the same volcanic system 

 as the volcanoes of Fuji, Hakone, Amagi^^ etc. which are constituted 

 of similar rocks, and to this group of volcanoes he confined the 

 application of the term " Fuji volcanic chain," excluding the 

 rhyolitic islands. As to the age relation between these two groups 

 of volcanoes, he supposed that the rhyolitic islands are older 

 than tlie volcanoes of " the Fuji chain." He was led to this behef 

 by the fact that basaltic éjecta cover the rhyolitic rocks at the 

 northern part of tlie island Niijima, and that the rhyolitic rocks 

 of the Idzu islands are correlative to similar rocks at the southern 

 extremity of the Idzu peninsula which are of the Tertiary period. 



FuKUCHi's view on the age relation between the rhyolitic and 

 basaltic islands was later endorsed by Tak. Katô'I Kôzu''^ also 

 pointed out that the rhyolitic rocks of the Idzu islands are 

 petrographically similar to the plagioliparite of the middle Tertiary 

 which occurs in the southern part of the Idzu peninsula. 



1) :km H^^ mm. 2) ^^ mm^ 



3) " Geology of Niijima." Feport Earthq. Invest. Co.n., Ko. 39, 1902 (in Japanese). 



4) 5^^ 



5) "The Land Slides in Kôzusbima," Heport Earthq. Invest. Com., No. 63, 1909 (in Japanese). 



6) "Geology of the Southern Part of the Idzu Peninsula," Jour. Geol. So<\ Tokyo, Vol. 

 XIX , p. 97, 1912 (in Japanese). 



