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on the earthquake and volcanic phenomena of japan, 301 



The Eruption of Bandaisan. 



On July 15 last year telegrams were received in Tokio that at about 

 7.30 A.M. a terrible volcanic eruption had taken place at Bandaisan. Snb- 

 sequently we learned that 695 people had been killed and 194 houses had 

 been buried or crushed ; while an area measuring 13 miles in one direction 

 and 8 miles in another direction had been covered with boulders, earth, 

 and mud. 



I first visited Bandaisan, which is situated on the north shore of Lake 

 Inawashiro, about 120 miles noi-th of Tokio, in 1879. I ascended the 

 mountain on its southern side, crossed over the summit, and descended 

 on the north side. The top of the mountain consists of one large peak 

 surrounded by three or four smaller peaks, one of which, called Kobandai, 

 or Small Bandai, has been blown away. From the fact that the whole 

 mountain was at the time of my first visit covered with trees and grass, 

 and that its general form was not that of a typical volcano, it was some 

 time before I was convinced that Bandaisan was really a volcano. How- 

 ever, from the fact that there was a tradition that in a.d. 807 the mountain 

 had been in eruption, coupled with the facts that there were hot springs 

 on its flanks, that such rocks as I saw were andesites, and that near the 

 summit, beneath the grass, I observed scoriaceous rocks, evidently the 

 outcrop of an old lava stream, I was led to describe Bandaisan as a still 

 active volcano. 



Previous to the explosion of July 15, it is said that two or three slight 

 earthquakes were felt, one of them occurring half an hour before the 

 violent eruption ; rumbling sounds were heai'd, and the day before the 

 eruption the flow of the spa near the top of Kobandaisan diminished. 

 This latter fact was not considered of importance, as the bathers knew 

 that the volume of water varied with the state of the weather, the 

 quantity of water being smaller when the weather is fine, and greater 

 when it is cloudy. In addition to this it is reported that the water in 

 certain wells diminished in quantity, and that wild animals exhibited 

 alarm. The water in the lake at the foot of the mountain, however, 

 showed no change in level. 



That the Bandai springs were subject to fluctuations according to the 

 state of the weather appears to indicate that the balance between the 

 internal forces which cause their flow and the outside atmospheric pres- 

 sure were of a delicate nature. The observations respecting the behaviour 

 of animals, of which there were many on the mountain, I myself having 

 come upon deer in what may have been the old crater of Bandai — assum- 

 ing the observations to be reliable — may be explained on the assumption 

 that they were sensitive to slight earth-tremors, it being now fairly well 

 established that animals like pheasants, horses, geese, &c., are certainly 

 extremely sensitive to slight earthquake distuibances. 



The eruption commenced with a violent shaking of the ground, and 

 •while the ground was moving there was a terrific explosion, followed by 

 about twenty other explosions. The result of this explosion was to blow 

 oat one side of Kobandai, leaving a horseshoe-like cliff crater, Ih square 

 miles in area; and, according to the calculation of Prof. Sekiya, to 

 remove 1,587 million cubic yards of material, weighing 2,982 millions of 

 tons, from the upper part of the mountain. This material, consisting of 

 earth and rocks, some of which were 30 feet in diameter, suddenly rolled 

 down the mountain with a velocity of about 48 miles per hour. To give 



