28 ^'ol- XLIIL, Art. C). — S. Tsuboi : 



a consideration of the morphologic features. Nakamura, Tekada, 



a,nd IsHiTANi'^ also support this view, stating : — 



" (According to an old record,) detonations like thunder were 



repeatedly lieard in Kyoto in an easterly direction, from Octoher 19th, 

 1112 till the end of Novemher, and the provincial government in Idzu 

 reported that an eruption had taken place in an island. (Tlie name of 

 the island is not stated.) . . . Assuming that this eruption took place in 

 Oshinja and the noises caused by it Avere heard in Kyoto, at a distance 

 of aliout 180 miles from the supposed origin of the distm-bance, Ave may 

 estimate at least the degree of the eruption in question. By the ex- 

 })losion of Krakatoa, the limit of audil)ihty of the noise was rouglily 

 speaking a circle with a radius ecpial to 2200 miles, when a circular 

 area in radius of about 4 km. was ])lo\vn away. In the eruption of 

 Bandaizan in 1888, the limit of audibility was about 10) miles, and the 

 corresponding linear dimension may be taken as 1 Im. Without enter- 

 ing into a discussion on the masses exploded off, let us assume that the 

 cube of hnear dimensions of the masses blown aAvay is proportional to 

 the square of the distance which sound reaches. Then we obtain from 

 the above data for Krakatoa that in Oshima a crater witli a radius of 

 0.75 ha. must have been formed by this explosion, while from those of 

 Bandaizan, we get 1.5 ha. as the probable radius of the crater. 



Now Messrs. Sato and Fukuchi consider tire large eastern gap of 

 the old crater wall of tlie somma to be the result of an explosion, .... 

 We consider tliis theory very probable, inasnmch as tlie theory of the 

 destruction of the crater wall by a lava stream fro.n the centi-al cone is 

 quite untenable, if we remember that a lava stream has generally not 

 such a greit velocity or momentum as to sweep before it an obstacle 

 some fifty meters high. The radius of this supposed explosion-crater is 

 estimated to be 1-2 hn. on the map. Comparing this theory with the 

 estimates given alcove, we may perhaps propose a In'pothesis that the 

 detonations lieard in Kjoto in 1112, Avere due to that explosion which 

 formed the eastern gap in the somma." 



1) "The Volcano of Oshima, its Past and Present," Froceediigs «f the Tokyo Ma!.lumatico- 

 T/ijjsiml Sorifti/, Vol. IV, 1908; Jour. Geor/r. Tokyo, Vol. XX., No. 23S, 19Ü8 (in Japanese). 



