116 Vol. XLIIL, Art. 6. — s. Tsubùi. 



— ill other words, the long physiographic history of Oshima, so far 

 as it can be traced back from structural study, is represented by 

 only one stage in the cooling history of the magma. 



(0) Future activity of tlie volcano Oshima. The volcanic 

 activity may depend upon many factors, of which the temperature 

 condition of the magma is no doubt most important. Other 

 conditions being equal, a rise of the magmatic temperature would 

 naturally bring about a rise in the volcanic activity, while a fall 

 in temperature would lead to its decay. In the volcano Oshima, 

 as already stated, the magma appears to have maintained the same 

 temperature throughout all the stages in the physiographic develop- 

 ment so far as is traceable. Moreover, the structural feature shows 

 that there has been no prolonged j^eriod of quietude in its life 

 history, there being many historical records of violent outbursts» 

 of which the latest one that lasted from 1912 to 1914 is still very 

 fresh in our memory. All in all, the volcano shows no sign of 

 decay in its activity and appears likely to retain for some time 

 the same energy which it has displayed in the past. 



Geological Institute, Science College, 



Imperial University of Tokyo. 



Published May lOth, 1920. 



