PUFF" CONES ON MOUNT USU 



Y. OINOUYE 

 Imperial Tohoku University, Sapporo, Japan 



Two days before the eruption of Mount Usu, in southwestern 

 Hokkaido, Japan, the writer arrived at the foot of the volcano. 

 He remained there for twelve days, watching every phenomenon, 

 going without sleep the first five days. The first explosion occurred 



Fig. i. — Sketch map of southwestern part of Hokkaido 



on July 25, 1 9 10, and others followed in rapid succession. Violent 

 eruptions ceased in about ten days and the writer returned to 

 Sapporo on August 7. He again visited the volcano in September 

 and in December of the same year, in May and October, 191 1, in 



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