ON SEISMOLOGICAL INVESTIGATION, 215 
III. Changes in the Vertical observed in Tokio, September 19, 1894, to 
March 1, 1896. 
Pendulum L.—On September 19, 1894, pendulum L, which has a 
boom about 5 feet in length, was installed beneath a wooden case on the 
concrete floor of a cellar in the N.W. corner of the College of Engineering 
at the Imperial University of Japan, in Tokio. When set up it had a 
period of about twenty-eight seconds, and 1 mm. deflection at the end of 
the boom which is in the meridian corresponds to an angular tilt of about 
0-5. Thedoubt expressed regarding the value of the readingsof this instru- 
ment arises from the fact that the notes relating to its calibration were lost 
by fire. When the readings increase in value the pendulum is swinging 
towards the west, which means that the ground may have been raised 
upon its eastern side. The diurnal motions of this instrument were small, 
not exceeding 1 or 2mm. For several days readings taken about 9 A.M. 
have been identical, after which there would be noted a displacement of 
lor more mm. For the first nine months these apparently sudden: dis- 
placements were towards the east. This was followed by three months 
of westerly motion, and then three months more of displacements towards 
the east. For the remaining three months, although the general direction 
of motion is westwards, it has been somewhat erratic in character. 
The readings given in the following table are in millimetres, and 
the date for any reading is the day on which there was a change from the 
reading which precedes it. 
Date Deflection Date Deflection 
1894, September . . 100 to101 || 1895, August 1 . : 79 \ 
October 1 . . 95 - Tea ‘ 80° 
- Oia s aa 96 - VRS Se ‘ 81 
4 18 , ; 95 oe 2 Oe ; 82 
+ 24. ; 96 | September 8  . 81 
5 Ske ¢ 95 % 10g fs 80 
November 24 | 102 | - oe ys 79 
cp 27 é 100 ~ 25m". 75 
re 30 r 97 i October 14 . = 73 
December 3 : 95 | ee dee al 74 
a 20 : 97 | wy MOG F 70 
1895, January 20 . : 89 | ree ee oe 66 
February 18 : 8§ <A Pai F 64 
March 10. s 86 i} a eG A 63 
en ee 85 i November 1. 60 
* April 38 : : 84 | is 24 , 59 
By 80 ‘ . 3 | December 8 é 64 
May6é6. ‘ a4 76 | be 16 : 63 
aes ie 3 a} 75 | 3 24 ‘ 64 
June 1] ; { 68 | 1896, January 10 . z 6L 
oa . ct 69 . fe OD : 60 
July 5 Z 3 70 % OR ‘ cai 
renege CU Z ; 73 February 9 x 67 
» 14 : =f 74 . 13 : 69 
» 18 E ; 76 s 16 ‘ 70 
» 27 - j 78 x 23 ‘ 68 
” 29 . 66 
' | 
| 
A fact of some importance connected with these displacements is that 
very many of them took place at the time of earthquakes which were 
sensible, and most of these small jumps were in the general direction in 
