564 REPORT — 1889. 



hypothesis and theory must starve without facts to feed on, it behoves us as work- 

 ing geologists to do our best to add to the supply. The success with wbich other 

 problems have been attacked by geologists forbids us to doubt that ere long we 

 shall have done much to dispel some of the mystery which still envelopes the ques- 

 tion of geological climates. 



The following Report and Papers were read : — 



1. Ninth Report on the Earthquake and Volcanic Phenomena of Japan. 



See Reports, p. 295. 



2. The Bandaisan Eruption, Japan, July 1888. 

 Bij C. MiCHiE Smith, B.Sc, F.B.8.E., F.B.A.S. 



Bandaisan is a mountain in Japan lying in Lat. 37°36' N. and Long. 140°6' E. 

 Before the eruption of July 15, 1888, there were three principal peaks— Obandai 

 and Kobandai, each about 6,000 feet high, and Kushigamine about 5,300 feet high. 

 The general result of the eruption was to Mow away 1,587,000,000 cubic yards 

 of the top of Kobandai and scatter it over an area of some twenty-seven square 

 miles. 



Immediately after the eruption Professor Sekiya and Mr. Kikuchi were deputed 

 to make a survey of the region affected, and their report has been published in 

 Tokio in the ' Journal of the Science College,' vol. iii., part 2, and in the ' Trans. 

 Seis. Soc. of Japan.' Perhaps the most striking feature of the whole eruption, 

 which was due simply to a vast explosion of steam, was the way in which the 

 shattered fragments of Kobandai poured down from the mountain in two great 

 earth-torrents, at a speed estimated by Professor Sekiya at 48 mUes an hour. 

 One of these — the smaller— was formed by materials projected over the shoulder of 

 Kushigamine and poured down the valley of the Biwasawa in a south-easterly 

 direction. The larger stream went nearly due north, burying a number of villages, 

 and, for a time, damming up the Nagasegawa. The photographs shown illustrated 

 some of the more interesting features of the eruption. The series of fifteen large 

 pictures was taken by Professor W. K. Burton immediately after the eruption ; 

 the series of smaller ones was taken by the author ten months later. The former 

 show the crater with the steam-jets still in very vigorous action, and give some 

 excellent views of the earth-torrents and of the damage done by them. They 

 show, amongst other things, the way in which the torrent flowed over obstacles 

 —in one case a hill nearly 200 feet high— and up the sides of the hills which it 

 struck at an angle. The second series show mainly the results of weathering and 

 the actioii of flowing water on the earth streams and crater walls. The first three 

 were taken on the Min.' stream. These show how the Biwasawa, which is only a 

 small rivulet, has already cut a deep channel through the loose earth. In one 

 place where it was measured the channel was 80 feet deep and 80 feet wide at the 

 top ; in other parts the depth was estimated at from 120 to 150 feet. No. 4 

 shows a part of the ruined forest above Nakanoyu. The forests all round, where 

 not_ protected by hills, were shattered mainly by a storm of stones of all sizes 

 projected by the explosion. Most of the trees were overturned and the remainder 

 were stripped of their leaves and twigs, and even of the bark, on the side facing 

 Kobandai. The density of the stone-storm may be estimated by the fact that seventy- 

 five marks of blows were counted on a quarter of a square foot of one of the tree- 

 trunks still standing near Numanotaira. The remaining photographs were taken 

 in the crater, and show its appearance after the action of rain, frost, and snow dur- 

 ing the winter. The steam jets are seen to be much less active than they were ; the 

 walls are much covered with loose debris ; and the sharp, conical mounds, which 

 formed a striking feature last year, are now much smoothed and rounded. 



The specimens shown were chiefly interesting as illustrating the way in which 

 the rocks have been decomposed by the action of steam, a fact which must not be 

 overlooked in estimating the causes leading to the explosion. 



