170 REPORT—1890. 
at the Meteorological Observatory in Tokio. In the instrument which is 
there used, which is Mascart’s, the needle of the electrometer, which has 
a bifilar suspension, is kept at the potential of the atmosphere by connec- 
tion with a water dropper, while the quadrants of the electrometer are 
kept at a constant potential by connection with 50 water Daniells. 
Through the kindness of the director of the observatory I was enabled to 
examine records extending over a period of twelve months. These 
records have been compared not only with the records of earthquakes 
observed in Tokio, of which there were 99, but also with the records of 
earthquakes felt in other parts of the empire, of which there were between 
four and five hundred. The results of these comparisons are as follows : 
1. In electrical disturbances which apparently accompany certain 
earthquakes the air almost invariably becomes electro-nega- 
tive. The change in potential is sudden, sometimes rising as 
much as 30 volts. It often takes several hours before the 
electrometer needle returns to its original position. 
2. At the time of earthquakes which have not reached Tokio, 
electrical disturbances have not been recorded. 
3. When Tokio has been at the 8.W. extremity of a disturbance 
shaking an elliptically formed area, the centre of which dis- 
turbance may have been 15 or 20 miles N.E. from Tokio, 
there have been three cases of electrical disturbance, and 
twelve cases without such disturbances. 
4, When the centre of a disturbance has been 50 or 60 miles N.W. 
of Tokio, there have been two cases of electrical disturbance, 
and eleven cases without such disturbances. 
. When an earthquake has shaken a narrow band extending 
from Tokio 30 miles northwards, there have been three cases 
of electrical disturbance, and no case of no disturbance. 
6. When the centre of a disturbance has been 20 to 30 miles E. of 
Tokio, there has been one case of electrical disturbance, and 
six cases with no disturbances. 
7. When the centre of a disturbance has been from 20 to 100 miles 
west of Tokio, there have been three instances of electrical dis- 
turbance, and three instances when there was no disturbance. 
8. If there is a feeble disturbance only felt in Tokio, such disturb- 
ances have been 13 times accompanied by electrical disturb- 
ances, and 31 times without. 
9. If there is a strong disturbance with Tokio near the centre, and 
shaking an area 60 or more miles in diameter, there have been 
ten cases of strong electrical disturbance, and only one case where 
there was no disturbance. Those earthquakes which are the 
most pronounced in relation to electrical phenomena have not 
always been accompanied by vertical motion, and they have 
occurred at different hours. 
Cr 
CoMPARISON OF ToKIO AND YOKOHAMA HARTHQUAKES. 
In Yokohama, which is situated about 18 miles 8.S.W. from Tokio, 
it has always been supposed that earthquakes are more frequent and 
more severe than in Tokio. The only lists of Yokohama earthquakes 
which I have been able to obtain extend from January 22, 1878, to 
December 31,1881, and from March 8, 1885, to December 31, 1889. 
a 
