96 



H. Simotomai — Taruinai Dome in Jajyan. 



middle of April, and it ended with the great explosion on the 

 12th of the same month. 



2. The lava followed this, and on the 19th of April it 

 accumulated in the crater so much as to be seen from a great 

 distance, and on the 23d of April the growth of the dome 

 was not vet completed and it was smooth and round-headed. 



3. On the 1st of May, 1909, the maximum growth of the 

 dome had already been reached, though we know neither the 

 exact time of its completion nor the exact shape at that time. 



Fig. 9. 



Fig. 9. Dome seen from the trigonometrical point on Higasiyama 

 (1016 m.) ; tracings from photographs to the same scale. A, view taken on 

 the 23cl of April, 1909, by Prof. Oinoue; B, view, on the 11th of May, 1909, 

 by Prof. D. Sato; 0, view, on 19th of October, 1916, by the author. 



The surface of the dome became very uneven through lateral 

 expansion, which was caused by the further accumulation of 

 lava. On the other hand, the sinking of the dome began 

 through the settling of the lava mass, and it probably ended 

 soon after the above date. Such depression after the maxi- 

 mum growth of the dome must have produced the change 

 from a small, round shape to the large, flat-headed one. 



4. As the parallel layers in the lava masses show, the 

 mode of growth of the dome was concentric, as suggested in 

 fig. 4, and the upper crust is split into irregular sections by 

 the sinking of the central part of the dome. 



