106 S. SEKIYA AND Y. KIKUCHI 



and ashes were ejected, but no stones. I reached Odera at noon, and 

 there I received surgical treatment, etc." 

 Deluge of rock The most striking feature in the whole of this eruption was the 



and earth. delude of rock and earth. Notwithstanding the violence of the 



phenomena, and the completeness with which the mountain was des- 

 troyed, the nature of the eruption was comparatively simple. The 

 destructive agency was merely the sudden expansion of imprisoned 

 steam, unaccompanied by lava flows or pumice ejection. When the 

 explosion took place, a considerable amount of rod; s and earth was 

 projected into the air, and a part diffused in the form of dust, but 

 by flu- the greater part of the bulk of Kobandai was just split into 

 mighty fragments, which were thrown down much after the manner 

 of a land-slip. Descending the mountain sides with ever accelerating 

 velocity, the components of these avalanches were dashed against 

 obstacles in their way and against each other, and were thus rapidly 

 reduced to confused masses of earth and rocks. The loose and friable 

 débris thus produced ultimately lost its adhesive power, and may have 

 been compared with a little exaggeration to sand. If we suppose a 

 mass of some 1.21 cubic kilometres, or 1,587 millions of cubic yards 

 (which was the actual volume of the mountain destroyed), of sand to 

 be suddenly precipitated from a lofty summit, it would flow down the 

 sides in a torrent not very unlike that of water. That the earth and 

 rock débris did flow down in this way we were convinced by examin- 

 ing the actual state of things on the spot, and more particularly by 

 witnessing afterwards with our own eyes a very similar phenomenon, 

 though on a vastly smaller scale. 



One day, while we were at work in the crater, a huge slice of the 

 precipitous wall of rock that had been bared by the explosion fell 

 suddenly and crashed with a tremendous uproar down the steep in- 

 cline beneath. This slab fell from a place about 300 metres high. The 



