ON THE EARTHQUAKE AND VOLCANIC PHENOMENA IN JAPAN. 90 



F rises on N.E. side 40 mm. 



Tremors on E and F are slight. 



2Iarch 12-15. (0"-43, 0"-2.5, 0"-26). 



The daily curve is barely visible on E, which shows small tremors. A 

 show.s curves, but they are irregular, and the N.E. sinks 15 mm. F rises 

 23 mm., that is, the direction of motion is contrary to A. Both A and F 

 show small tremors. 



March 15-19 (0"-43, 0"-25, 0"-26).— E clock stopped, and therefore 

 no records until end of month. From the 15th to 16th A was steady, 

 but from this date onwards it gave large daily curves. 



On the 15th, and at 3 a.m. on the 18th, there were earthquakes. 

 During the three days A rose 9 mm. F does not show daily curves, but 

 it rose 39 mm. 



The conclusions I arriv^e at respecting this section of the i^eport is, 

 that instruments on the sui-face and underground show diurnal move- 

 ments, which closely agree in the times at which they occur. These move- 

 ments are most pronounced underground by pendulum E, the excursions 

 of which have in nearly all instances been greater than those shown by 

 pendulum A in my house. The crest of a wave which corresponds to a 

 N.E. lifting on A and a S.E. lifting on E has usually been reached 

 between 4 p.m. and 10 p.m., the movement in the opposite direction being 

 completed between 5 a.m. and 10 a.m. It does not seem that air temperature 

 has had any measurable effect in the production of these movements, because 

 they have been most marked beneath the surface, where the change in 

 temperature during twenty-four hours has practically been zero. The 

 opportunities for observing whether they hold any relationship with rain- 

 fall have been few. It is possible that the rainfall of March 16 and 17 

 may have been connected with the large motions of A between March 16 

 and 18, but the largest motions of E on March 1 and 2 occurred during a 

 dry period. After the rainfall of January 25 and 26, and again after 

 that of Februaiy 8 and 9, it may be noticed that the time at which E 

 completed its N.W. excursion was delayed, while after that of March 16 

 and 17 pendulum A was delayed in its N.E. movement, and these are the 

 only occasions on which rain fell in any quantity. 



{j) The Wandering of the Pendulums. 



The following table shows the daily change which has taken place in 

 the position of the pointer of pendulum A, and for a few days that which 

 has taken place with pendulums F and E. The numbers indicate so many 

 millimetres of motion. The sign + prefixed indicates that the scale 

 i-eadings were increasing, while the sign — indicates that they weie 

 becoming smaller. When the signs for A and F are similar, then these 

 two pendulums were moving in the same direction. The difference 

 between the readings of an instrument when a new film was put on and 

 when it was taken off gives the distance through which a boom has been 

 displaced during periods of three or four days : this quantity is also ex- 

 pressed in seconds of arc. The fifth column gives the rainfall in milli- 

 metres, and the sixth the number of hours of sunsliine, but only between 

 February 25 and AjDril 30. These latter records were taken for me 

 by my colleague, Prof. W. K. Burton. 



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