H. Simotomai — Tarumai Dome in Japan. 89 



Oinone again visited the mountain and the photographs taken 

 on that date show a smooth, round-headed dome which filled 

 the inner crater and rose more than 100°" above it. The pic- 

 tures taken on May 1st show the dome to have become larger 

 and flatter at the top. 



The trigonometrical measurement of the Oinoue party on 

 May 1st gives the dimensions of the dome. The base of the 

 dome was about circular, covering an area of 152,000 sq. m. It 

 was about 200" in height above the floor of the crater bottom 

 and 131:"' above the lowest part of the inner crater-wall; its 

 whole volume was computed at 20,000,000 cubic meters. 



The dome was 1016"' high above sea-level and 30"" above 

 Higasiyama, so that the volcano had become a little higher 

 than before. On May 15th an explosion occurred on the south- 

 ern foot of the dome and thereby the inner crater- wall was 

 cracked. The new fissure was 3°" to 8°" wide, about 18"" in visi- 

 ble depth, and 150''' long in the direction of K.GO^W., ending 

 directly on the side of the dome. From a point in the middle 

 of the crack, sulphurous gas was issuing in great volume. In 

 the winter of the same year snow covered the dome, though it 

 was still fuming on the surface. 



After that time seven years elapsed without any further 

 information about the dome. The writer had occasion to visit 

 it three times in the year 1916, and will give here some short 

 observations about the development of the dome, adding some 

 new data to that of my former publication.* 



Since 1909 the dome has remained without any important 

 change in form, conserving all the main elevations and angles, 

 and most of the large lava blocks scattered in the vicinity had 

 kept their original shape. Talus had developed on all sides, 

 covering the lower three-fifths of the dome. Its maximum 

 development is at the southern half, where the prevailing wind 

 attacks it directly, while the minimum is at the opposite side, 

 Avhere the dome is protected from the wind through the inner 

 crater-wall. The southeastern side of the mountain near the 

 termination of the large fissure shows the least steepness caused 

 by the falling of lava, and it is now not difiicult to reach the 

 summit, which was never visited by anybody before and it was 

 doubted whether there existed any crater or not. 



From out of the talus arises the dome proper, showing steep 

 cliffs of lava in its sides which are very instructive. 



The superficial lava layer does not form a continued crust 

 but is broken by vertical fissures into many irregular parts, 

 some of which are fallen down between others as wedges. 

 Each lava-mass is divided into numerous layers, feldspathic, 

 iron-rich, etc. These layers must originally have been parallel 



* Zeitsclirif t, Gesellsclaaft fiir Erdkande, Berlin, 1912, page 43B. 



