DEVELOPMENT OP SEISMOLOGY IN JAPAN 287 



island of Sakurazima was estimated at 2 m. In the meanwhile, 

 horizontal displacements of 3 to 4 m. have also been discovered. 



The distribution of the regions where the sound and air waves 

 due to the eruption were felt, as well as those places where the ashes 

 ejected were scattered, were fully investigated. ^^^ 



The latter subject has also been studied by S. Fujiwhara^^' who 

 developed his mathematical theory on the anomalous propagation of 

 sound in the atmosphere which is well known to meteorologists. 



The hot springs region of Mt. Hakone was visited by a swarm of 

 local shocks in Jan., 1917, which caused a panic among the inhabi- 

 tants. It is recorded that a similar activity was experienced in the 

 spring of 1786. The time distribution of the shocks studied by Saem. 

 Nakamura ^'^ resembled that of the ordinary volcanic earthquakes, 

 though no proper volcanic activity was observed, nor could it be 

 expected from the dormant state of this ancient volcano. Only, on 

 the end of March, the hot springs of Oowakudani displayed unusual 

 activity. A similar activity was repeated afterward in December, 

 1920.^") 



Another swarm of weak shocks experienced in Suwa hot spring 

 district in May, 1922. ^^^ This type of earthquakes is worth special 

 notice, since the mechanism of these phenomena may represent a 

 miniature of that of earthquakes on a larger scale. 



The annual and daily frequency of volcanic activity and its 

 relation to atmospheric or tidal condition has been investigated 

 statistically by Omori.^^^ He found, with respect to the monthly 

 number of erui^tions that the activity of inland volcanoes is associated 

 with the fall of bai-ometric pressure, while the volcanoes on islands 

 are sensitive to the fall of sea-level. Later, the subject was resumed 

 by S. Kanda^''^ who calculated the correlation coefficients with regard 



(1) Omori, Bull., 6, No. 1 (1912); 7, No. 1 (1914); 8, No. 2 (1916); 8, No. 3 

 (1916). S. Ootuki, J.M.S., 32 (1913), 61, 113. Y. Yosida, J.M.S., 33 (1914), 257. K. Hasegawa, 

 Kisyd-yoran, March, 1914. 



(2) Bull. C.M.O., 2, No. 4 (1916); T.S.B.K., 6 (1911), 132. Also K. Aichi, 

 N.S.B.K., [iii] 2 (1920), 63. 



(3) J.M.S., 36 (1917), 67. Also Miscell. Art., J.M.S., 36 (1917), 319. 



(4) Miscell. Art., J.M.S. 40 (1921), 36. 



(5) Saem. Nakamura, J.M.S., 41 (1922), 233, 629. 



(6) Ho., 56 (1907); Bull., 5, No. 1 (1911); 6, No. 1 (1912), No. 3 (1914); 7, No. 

 3 (1911); 8, No. 2 (1916); J.M.S., 29 (1910), 87. Also I. Hattori, J.M.S., 30 (1911), 5. 



(7) J.M.S., 39 (1920), 222. 



