300 T. Terada and T. Matuzawa 



obtained they point out some anomaly observed in the month follow- 

 ing the great earthquake. 



The importance of investigating the variation of latitude was 

 recognized early by the E.I.C. The observation was begun in 1895 

 in Tokyo by H. Kimura. Afterwards, the work was transferred to 

 the Geodetic Committee and carried out continuously in Mizusawa 

 according to the international scheme. Kimura's discovery of the 

 2-term and his subsequent contributions in this line are well known.^^^ 

 Omori^-^ remarked some possible relation between the occurrence of 

 destructive earthquakes with the extreme values of latitude. In the 

 most recent report by Kimura^"'^ the resurue of the variation of latitude 

 from 1918.0 to 1923.9 is given. It is interesting to observe that the 

 deviation of the earth's pole showed a rapid turn in the epoch 1923.8 

 - 1923 9, viz. near the occurrence of the great earthquake, though of 

 course it njay be merely a matter of accident and the author has 

 adduced no speculation on this point. 



It may perhaps be added here that S. Shinjo*^^^ disc ssed the 

 possibility of explaining the physical meaning of the 2-term by the 

 influence of atmospheric refraction. I. Yanjamotu'^''^ carried out a 

 special series of observations with the purpose of testing his idea. 

 The final decision has not yet been given, though the results thus far 

 obtained seem to be not altogether unfavourable for his theory. 



The possibility of detecting some change going on underneath 

 the earth's surface by the observations of the terrestrial magnetic 

 elements had occurred early to the pioneers of the E.I.O. Fiv^e 

 Magnetographic Stations were established in different selected districts 

 for investigating the changes of the magnetic elements which might 

 appear associated with earthquakes. Some examples of such changes 

 were cited in Kikuchi's Keport. Later, Tanakadate perceived the 

 necessity of increasing the sensibilities of the recording instruments to 

 extreme values and constructed, with the able aid of H. Kadooka, a 

 set of extraordinarily sensitive self-recording instruments. With these 

 instruments, the observations were carried out at Aburatubo, Misaki, 

 for a few years. The results, with some discussion, have been reported 



(1) T.S.B.K., 1 (1902), 35; 2 (1905), 357; Astron. Nachr., No. 3783; A.J., 517, 



(2) Pub., 18 (1904). 



(3) Jap. J. Astr. Geophys., 3 (1925), 153. 



(4) Mera. Kyo., 4 (1912), 287, 325; T.S B.K., 6 (1912), 236. 



(5) T.S.B.K., 9 (1918), 387. 



