VI PREFACE. 



T. Ta M ARU, Rigalcusi, 



Now Asst. Prof, of Physics, Imperial TTniversity Tokyo. 



T. To:\roDA, Rigahusi, 



Now Prof, of Pliysics Dai-iti Kütögakkö, Tokyo. 



D. Sltto, Rigahisi, 



Now Prof, of Physics, Dai-iti Kötügakko, Tokyo. 



S. Saxo, Rigalcusi, 



Now Prof, of Physics, College of Naval Engineering, Yokosuka. 



S. SlNZYo, Rigalcusi, 



Now Asst. Prof, of Physics, Imperial University, Kyoto. 



;M. Hattort, Rigalcusi, 



Now Prof, of Pliysics, Naval College E lazima. 



A. Taxa K a date, 



The writir. 



The writer wishes specially to remember Prof. Dr. D. 

 Kiknti, Baron, the President of the Earthquake Investigation 

 Committee at the time, whose interest on the subject and whose 

 cordial advice both official and scientific was of great encourage- 

 ment to all of us. Thanks are also due to various public authori- 

 ties and private persons who assisted the ol)servers in selecting 

 the stations ; and to the three computers Messrs. T. Kariya, 

 Rigalcusi, S. Kttsakahe, Rigalcusi and Y. Yasuda, graduate of 

 the School of Physics in Tokyo, who performed that tedious 

 work with care and patience. 



The spelling of Japanese names adopted in this volume is 

 slightly different either from that in common use among English 

 speaking people in this country, or from that of the Romazikwai 

 system to which the writer is an opponent. The Goveriuiient 

 Committee for the Improvement of the Language has lately 

 brought forth a system which is a kind of compromise between the 

 previous systems. At such a stage of orthographical reformation 

 one might be excused to adhere to what he believes the best. 



