248 Scientific Intelligence. 



The mountain of Baldai-san was an extinct volcano, but had 

 one steaming fissure. On the 14th of July, at 10 a. m., the spring 

 at the Spa on the mountain became dry. The next morning, the 

 15th, it was full again. At 7 h. of that morning, light earthquake- 

 like rumblings were noticed; at 7 h. 30 min., there were loud and 

 heavy shocks; at 7 h. 45 min., the eruption began,, about 120 

 yards from the steaming fissure. A dense column of steam and 

 dust shot up with tremendous noise. 15 to 20 explosions occurred 

 of a minute or more each;, and the vapor and dust were projected 

 to a height of 4000 to 14000 feet, and spread into a canopy of 

 much greater height, making pitchy darkness around. About the 

 crater, a tempest raged of hot blasts of steam, wind, thunder, 

 lightning, volcanic dust and falling stones, and, for five minutes, 

 rain ; the prostrated trees fell with their heads away from the 

 crater. Within fifteen minutes of the outbreak a land-slide started 

 from the summit, probably promoted by the shower of water, 

 stones and rock-masses, and descended with terrific speed, burying 

 the Nagase valley with its villages, and devastating an area of 

 27 square miles. Some of the masses transported by the land- 

 slide were over 30 feet each way. 



The violence was ended in less than an hour, when the darkness 

 became that of twilight on a rainy evening ; and in five hours the 

 dust-fall had wholly ceased. The dust was drifted southeastward 

 to the seacoast, where, 62 miles from the volcano, the area cov- 

 ered was 30 miles wide ; but the deposit made there only traces 

 of a film over the surface, and w T as but a foot deep on the leewai'd 

 slope of the mountain. This dust was not ordinary glassy vol- 

 canic ashes, but like dust from abraded volcanic rock. There 

 w T as no flow of lava. 



Mr. Kikuchi concludes from the absence of any lava-flows and 

 the character of the dust, that no lava was concerned in the erup- 

 tion. In that case, unlike the explosive eruptions of Krakatoa and 

 Tarawera, the vapor producing the explosions was generated 

 above the level of liquid rock, the opened fissure permitting en- 

 trance of water only to a depth short of that where fusion existed. 

 The chief rending and projecting force of the explosion would, in 

 any case, have been below at the depths where the sudden gener- 

 ation of the vapor took place; and from the subterranean region, 

 the rocks and stones, and the dust that abrasion could make, would 

 have been thrown into the air to fall around, the lighter part to 

 be drifted by the winds as it fell. The steam, after escaping into 

 the air, would have already expended the chief part of its energy 

 and could therefore have produced comparatively little effect on 

 the outside walls or the summit peaks of the mountain. There 

 would have been undermining by the ejections, and a correspond- 

 ing loss to the mountain from subsidence ; and there could not 

 have been the supposed " blowing away " of even the millionth 

 part of "2782 million tons" from the summit, the amount esti- 

 mated as lost by the mountain. 



Such an eruption is a semi-volcanic explosive eruption, suppos- 



