94 II. Slmotoraai — Tarumai Dome in Jajpcm. 



In October, 1916, we carried a small transit and a mountain 

 barometer to determine the exact height of the dome. For the 

 measurement of the heights, I took one point common with 

 the former snrve_y as a base, that is, the triangular point of 

 Higasiyama, 1016"" high above sea-level. From this base, I 

 took the readings of the several characteristic points on the 

 dome, upon which the former surveyor and I had agreed. 

 This method gave the same result as that furnished by the 

 mountain barometer. The exact height of the dome is 1035"". 

 Comparing this measurement with that made by Oinoue on 

 the 1st of May, 1909, my result is 11"' less, so that we can be 

 sure that the dome has sunk a little since the 1st of May, 

 1909. But this sinking of the dome surface ended probably 

 before the summer of 1909, for since that time it has remained 

 practically the same in size and the shape, so far as I remem- 

 ber it. 



On the slaggy surface of the dome, much f ragmental material, 

 similar to that seen all around the base, is scattered. This 

 material might be regarded as having been thrown up by the 

 explosion on the 15th of May, 1909. 



In August, 1916, I found many dead cicadas {Cicadina hi- 

 harnata Motsch.) on the dome, which perhaps w^ere traversing 

 the mountain and were killed by the sulphurous gas. 



It is of further interest that three species of plants are found 

 on the dome surface; these are: 1, Pentstemonfrutenscens 

 Lam.; 2, one species of moss resembling Decranum sp.; 

 3, another species of moss resembling Pognatum sp. The 

 two latter have not yet been classified by species. The first of 

 them was determined by Prof. Miyabe in Sapporo. It is very 

 common on the high mountains of northern Housyu and Hok- 

 kaido, and it was first found in Japan on Tarumai ; so the 

 name " Tarmai-S6," or grass of Tarumai, is applied bj^ him. It 

 is not strange that this plant, whose dry seeds weigh only 

 about 0*002 gi'am, has migrated to this dome from the 

 outer slope of Tarumai, but it is remarkable that the develop- 

 ment succeeded in only seven years on the still fuming lava 

 dome. 



The smoke is continuously issuing with much violence from 

 the same point of the main fissure on the inner crater wall as 

 before. 



In January of this year, under the smoke column, the dome 

 stood covered with snow except in the middle belt, where the 

 cliffs show their maximum steepness, and also at several fum- 

 ing spots on the top. 



Sainmary. 



\. The activities preliminary to the 1909 lava eruption con- 

 tinued about four months, from the middle of January to the 



