HORIZONTAL. PENDULUMS. 141 



by a short interval of irregular movements, the period, nveraged 

 from 103 vibrations, being 6.0 seconds. I^ater on, the peiiod 

 a,vêraged from 68 vibrations was 7.0 seconds. 



Tlie EW component. The motion was small and complex 

 during the first 50 seconds, quick vibrations being superposed on 

 slow undulations. The motion became then regular and larger, 

 till at 90 seconds from the commencement the writing i)ointer 

 went off the smoked paper, when the amplitude became greater 

 than 13. Ô mm. and therefore the range of motion greater than 

 27 nun. The period of this vibration being about 8.5 seconds its 

 maximum velocity and maximum acceleration would be respective- 

 ly greater than 10 mm. per sec. and 7.4 mm. per sec. per sec. 



One of the after-shocks of this earthquake, which took place 

 at 4.54.0. a.m., is shown in figs, 17 and 18. The total duration 

 was about 9 minutes. The motion began with 6 undulations of 

 the average period of 10 seconds, the maximum range of motion 

 being 0.3 mm. in the EW and 0.2 mm. in the NS component. 

 The next 9 undulations were a little quicker, their average period 

 being 6.1 .seconds. The average period near the end was 4.6 

 seconds. 



22. As examples of earthquakes, whose origins are at such 

 distances from the observing station that the movements can no 

 longer be registered by ordinary seismograghs, I take those shocks 

 which occurred on the lOth and the 12th August, 1898, and on 

 the 7th October, 1898. 



23. The earthquake of the 10th August, 1898 ; 10. 0. 41 p.m. 

 The meizoseismal area, in which buildings were damaged, 



landslips produced, etc., was a limited portion of the west 

 of the Province of the Chikuzen (in the Island of Kiushiu), 

 about 900 km. W SW of Tokyo. The total duration was about 



