S5§ 



SCIENTIFIC NEWS. 



[Nov. 30, 1888. 



layer gradually diminished in thickness, till at the coast 

 it was a barely perceptible film. The noises of the ex- 

 plosions were heard some thirty miles to windward of 

 Bandai-san, and 62 miles to leeward. But the earth- 

 quake which preceded and attended the outburst, though 

 so prolonged and terrible in intensity, was, strange to 

 say, not felt beyond a radius of thirty miles from the 

 volcano — a fact accounted for by Messrs. Sekiya and 

 Kikuchi on the ground that the seat of violent action was, 

 doubtless, but a little way below the earth's surface, if, 

 indeed, not above the mean periphery and in the bowels 

 of the mountain itself. Steam — a well-known and 

 powerful cause of seismic phenomena — was, as has been 

 already indicated, the agent of the explosions. The great 

 volumes of steam that must be generated whenever, from 

 any cause, subterranean waters are brought into contact 

 with the molten interior, expand and fill up the rock- 

 fissures. If not deep enough down, or if lacking suffi- 

 cient pressure and volume to break through the superin- 

 cumbent masses, such ebullitions, though they may 

 wrench and strain and tear the earth's crust internally, 

 are yet hopelessly imprisoned, and can only produce on 

 the surface the phenomeraof earthquakes or minor seismic 

 vibrations. But there are cases — happily none too 

 common in this our day — when the pent-up vapour suc- 

 ceeds in bursting open its prison roof along some line of 

 least resistance and working havoc on a prodigious scale. 

 Of such was the explosion which lately rent Sho- 

 Bandai-san in twain. 



Besides the lighter erupted matter, whose nature and 

 behaviour have been sketched above, there was the solid 

 body of the peak itself, which, tossed in gigantic masses 

 high into the air, fell upon the slopes and glens, and, 

 rushing down them with fearful velocity until brought to 

 rest on level or nearly level ground or by impassable 

 obstacles, buried twenty-seven square miles of country 

 fathoms deep in debris, in the short space of about ten 

 minutes from the first explosion. One of the toughest 

 of the many problems which beset the Japanese investi- 

 gators was that of accounting for the wonderful and 

 apparently eccentric fashion in which this mighty volume 

 of matter had been propagated and disposed. Per- 

 severing examinations, however, soon brought them to 

 intelligent conclusions; and these were confirmed 

 before the very eyes of Professor Sekiya by an occur- 

 rence which, though doubtless gratifying to that ardent 

 seismologist, was not, as he drily remarked, a particu- 

 larly comfortable incident of a solitary ramble. One day, 

 while he was at work in the crater, a huge slice of the 

 precipitous rear-wall that had been bared by the explo- 

 sions fell of a sudden, quite near to but happily clear of 

 him, and crashed with a tremendous uproar down the 

 steep mountain side. This slab was about 1,000 feet 

 high and of considerable thickness. He witnessed its 

 fall and its long descent. He saw how the great masses 

 of earth and rock were shattered as they fell, and broken 

 up into bits ever growing smaller as the velocity and the 

 distance increased and as the fragments were dashed 

 against one another and against obstacles in their way, 

 until they finally lost cohesion, and were reduced to a 

 pulverised, almost impalpable state, not very different 

 from that of sand. The behaviour of the mass now re- 

 sembled the rush of a headlong torrent. Tough boulders, 

 able to survive the ordeal, were of course mixed with 

 the finer matter, and great rock masses from 20 to 30 

 feet in diameter were floated down on the surface. But, 

 as a whole, the movement approximated to that of a fluid. 



No words, says the Professor, can describe the " fiero 

 ness and force " of that magnificent and impetuous dowi 

 pour — its mad surgings this way and that, and the bol 

 leaps with which it would now and then bound over lc 

 hills that hindered its progress, and shot onward dow 

 the neighbouring depression. Similar, though on a vast 

 greater scale, must have been the awful avalanch* 

 which darted down from Sho-Bandai-san in two pri 

 cipal streams on the fatal morning of the 15th of Jul 

 These, it is now known, dashed over hills and ridg 

 fully 100 feet in height, and Professor Sekiya's estima 

 that they must have attained a velocity of nearly 50 mil 

 an hour sufficiently accounts for the swiftness of t) 

 fate that befel the doomed peasantry in the uplands ai 

 valleys below. A part, doubtless, of the descendii 

 matter, mingling with the waters of ponds and lakes 

 its course, became a kind of mud, and may have be< 

 thus assisted in its flow ; while that which reached t 

 Nagase river and swallowed up so many of the Nagasa 

 villagers, acquired the consistency of a paste. But by 1 

 the greater volume was never moistened, and must ha 

 derived its fluid or semi-fluid properties from a rap 

 process of pulverisation, after the manner witnessed 

 Professor Seki3'a. 



As for the crater, the researches conducted by t 

 Japanese explorers now assigned to the disrupted mat 

 dimensions far in excess of all previous estimates, 

 form, the crater-bed is roughly that of a horseshoe, op> 

 ing northward, and inclined slightly down from the aj 

 to the mouth, where it is nearly 1-5 mile wide, 

 whole aiea is about 950 acres. Round the crown of 

 shoe is a nearly vertical wall, 1,660 feet high, in front 

 which everything has been blown away. But the p< 

 itself, which was 540 feet higher than the summit of 

 crown, lay within the now empty space. Thus, the th 

 greatest dimensions of this gigantic projectile were, 

 spectively, about 2,200, 7,500, and 7,800 feet. From th 

 and other particulars it has been possible to estimate v 

 approximately both the volume and weight of the t 

 rupted matter. In my former narrative I ventured 

 the statement that, assuming the mean depth of de. 

 over the buried area to be 15 feet, its weight would 

 be less than 70c millions of tons. I added, however, 1 

 this depth was probably far short of the truth. It pro 

 to be only about one-fourth of the truth. No fewer t! 

 1,587 millions of cubic yards, weighing 2,880 millions 

 tons, and spread over 27 square miles of country to 

 average depth of 57 feet, are the approximate figr 

 with which to estimate the power exerted in this la 

 manifestation of plutonic energy. A great fissure, doi 

 less corresponding with the original line of least resistai 

 runsthroughthe crater from its vertex nearly to its moi 

 It is marked by a long range of steamjets, large 

 small, which puff and hiss forth immense volume: 

 white, pungent vapours. But Bandai-san is now J 

 fectly at rest. Delicate tromometers fail to detect 

 faintest throb upon its surface. Only that row of 

 remains to tell of the fever that rages far beneath. 



The terrible coups de vent that accompanied the 

 plosions, and wrought such havoc in the forests . 

 villages, were, of course, corresponding phenomenE 

 those which break windows and lay low the grass 

 plants at the firing of ordnance forged by men. 

 difference was one of degree only, though some ide; 

 its vastness may be gathered from the fact that in ' 

 case villages many miles from the scene were liter: 

 wrecked, while in the forests near the crater hundr 



