Volcano üshima, Idzu. 129' 



Thns, the previous writers agree on the thne relation between 

 the rhyolitic and basaltic islands, and are inclined to consider, with 

 varying emphasis, that the former are older than the latter, being 

 correlative to the Tertiary rhyolitic bodies in the Idzn peninsula. 



The sequence of the lavas as above being harmonious with 

 that in North Japan, where pre-andesitic vulcanism is represented 

 by plagioliparite mostly of the Tertiary period' \ the above view ha& 

 been generally admitted by geologists. 



Very recently, Tsujimura'^ opposed this generally accepted view. 

 He noticed that Niijima and Kozushima are too young in their 

 morphogi-aphic aspect to be Tertiary volcanoes, and came at last 

 to doubt if they are really so old as has been generally supposed. 



On the other hand, Ômoei and Nakamuea enumerate in their 

 historic records volcanic eruptions which they consider to mean 

 those of Kozushima in 838'^ and of Niijima in 88(V\ 



1) B. Koto, " Volcanoes of Japan," Jour. Geol. Soc. Tokyo, Vol. XXHI., p. 5, 1916. 



2) « Kozushima and Nüjima," Report Earthg. Invest. Com., Ko. 89, 1918 (in Japanese). 



3) Zoku-Kihon-Koki {^^ H ^^tS) records that from August 15, 838 (/pi^nS^-t: B §t@+ A H ) 

 for more than two months, some minute powders Jike ash fell in the provinces of Kawachi, 

 Mikawa, Tôtémi, Suruga, Idzu, Kai. Musashi, Kazusa, Mino. Hida, Shinano, Echizen, Kaga, 

 EtchÛ, Harima, and Kii. Some authors consider this as an eruption of Oshima, while Omori 

 pointed out that this must mean an eruption of KOzushima for in the same book are found 

 the fo'lowing lines : — 



mmmm^, ^^y^m is;s:w^*o äj^a-et^^^ ^mmê^y • ■ ■ êt^Mî^o 'j^rïi^^ito ^iê 

 mM^mmmo Att$n7K3 m±i^^o Bikmmo -^^mmn, ^\[kmai, m^^kMo ^mm'^o m 



"Jt3^Ä" ill ^^6 above description must mean Kozushima {Tf^^ëj)'> " Sffi'ifïOîi^î^ 

 corresponds to the village, KOzushima-mura, on the west coast of the isLand ; and " Ä^:iL4fcÄo 

 ^mmmUo Ä*>tiJo e,^Sm^o ^mA^t^^. ^mm^^r l. a description of Tenp- 

 yama (%^\lil fetanding at the northeastern part of the island. 



4) Sandai-jitsurokn (Hf^S^) records that on Jiüy 3, 886 (t*II^^Äfl + P-l B ). there was 

 observed in the province of Awa, toward the south, a very thick dark cloud, in which lightning 

 flfishes -were sten, thurdering noises and earthquakes continuing all night. The sky did not 

 clear up till the morning of July 5 (31fl-+:^B), ^hen the earth was covered with ashes two 

 or three imhes thi<k. On the other hand, it is told, according to Nihonkiryaku (H?^*EB&) and 

 Fusôryakki (:Î^^P^SuS that in 887 the provincial government oï Idzu presented the central 



