DE VELOPMENT OF SEISAIOLOG Y IN JAPAN 295 



bers of the E.I.C., A. Tanakadate and H. Nagaoka stood foremost in 

 this line of attack. Numerous investigations on various subjects, 

 though apparently remote from the field of practical seismology, but 

 of prime importance in the scientific study of earthquake phenomena, 

 owe their initiation to the proposals of these eminent scholars. 



The determination of the acceleration of gravity was made early 

 in 1881-1884 by Tanakadate and others*^^^ in a few stations, after the 

 memorable work of Mendenhall on Mt. Huzi in 1880. Systematic 

 measurements in different localities all over the land was planned and 

 has been carried out since 1900, under the auspices of the Interna- 

 tional Geodetic Committee. "^^^ It was H. Nagaoka himself who led 

 the earlier expeditions, in the meanwhile improving and elaborating 

 the apparatuses and methods of observations. The work has been 

 continued by the competent hands of S. Shinjo, T. Shida, R. Otani, 

 M. Matsuyama and others. The complete report of these recent 

 labours has not yet been given out.*^^^ It is beyond doubt that the 

 full data obtained, if properly examined, will not fail to throw 

 considerable light on the distribution of the earth mass in this part 

 of the earth crust and thereby afford us a tangible clue for grasping 

 the actual mechanism of earthquakes. Matsuyama^''^ has already taken 

 a step toward this direction. He observes that the anomalies of gravity 

 along the Pacific and the Japan Sea coast are inexplicable as the 

 effect of mere topography. Moreover, he remarks the tendency of the 

 districts most frequented by earthquakes to be associated with apparent 

 defects of subterranean mass. 



Nagaoka "^^^ elaborated the design of a pendulum for the deter- 

 mination of g, made with metallic tungsten, the material which is 

 gifted with unique properties suitable for the purpose. The instrument 

 was recently constructed in the Institute for Physical and Chemical 

 Research, Tokyo, and will be later used in the expedition in Manchuria. 



(1) Memoirs of the Science Department, Imp. University, Tokyo, No. 5 (18S1) 

 and Appendix. 



(2) Nagaoka, Shinjo and Otani, T.S.B.K., 1 (1901), 6. Shinjo, Otani, Shiraidzu, 

 Shida and Homma, ibid, 1 (1903), 178. Shinjo, Otani and Yamakawa, ibid, 2 (1903), 41. 

 See also T. Takaraine, T.S.B.K., 7 (1914), 265. 



(3) The results obtained up to 1906 are summarized by E. Eorras, Comptes 

 Kendus des Seances de la 6 me Conference Generale de I'Association Geodesique Inter- 

 nationale, 3 (1911). 



(4) The Report cited above. 



(5) N.S.B.K., [iii] 1 (1919). 347. 



