ON THE EARTHQUAKE PHENOMENA OF JAPAN, 211 
Report of the Committee, consisting of Mr. R. ETHERIDGE, Mr. 
THomMAs GRAY, and Professor JoHN MILNE (Secretary), appointed 
for the purpose of imvestigating the Earthquake Phenomena 
of Japan. 
Owrtxe to my absence from Japan, on a visit to Europe, during six 
months of the past year, and a complication of circumstances involving 
the removal of my seismological laboratory, over which I had no control, 
the work accomplished in actual observation has been small. 
While passing through America, and subsequently when in Italy, I 
saw and learnt much respecting observations which may with advantage 
be amplified and repeated in Japan. 
When in England, I entered, in conjunction with Mr. Thomas Gray, 
into arrangements with Mr. James White, of Glasgow, for the construction 
of aseismometer. This instrument, which gives a complete diagram of 
all the sensible vibrations of an earthquake in conjunction with the time 
of occurrence of these vibrations, was exhibited before the Geological 
Society of London, and is described in their ‘ Proceedings.’ ! 
The instrument is now in Japan. By request it has been exhibited to 
His Imperial Majesty, the Mikado of that country, and very shortly it will 
be erected, in all probability, at the Meteorological Observatory in Tokio. 
One class of phenomena which I have been engaged in observing 
since my return to Japan, is earth-tremors. These microseismic move- 
ments of the soil I observed some years ago, with an instrument similar 
in principle to the apparatus used by Messrs. George and Horace 
Darwin, at the Cavendish Laboratory, when engaged in the attempt to 
measure the lunar disturbance of gravity.” 
The apparatus that I have employed during the last five months is 
similar to the Tromometer of Bertelli and Rossi. It consists of a weight 
suspended by a very fine wire, the whole being enclosed in a tube, for 
protection against currents of air. Projecting downwards from the 
weight there is a stile, which is observed with a microscope containing a 
micrometer scale. The whole, which is supported on an iron stand, rests 
on the head of a stone column, The column is about ten years old. It 
is inside a brick building, from the walls and floors of which it is com- 
pletely detached. 
Hitherto I have not had the time which is necessary to analyse the 
mass of observations which have already been accumulated, but the 
following points are very clear. 
1. It is but seldom, if ever, that the pendulum is completely at rest. 
2. A vertical motion is occasionally observed in the pendulum, the 
stile of which oscillates up and down with a rapid tremulous movement. 
3. At times the horizontal swing of the pendulum is very irregular, 
the oscillations being performed in short jerky swings which vary in 
amplitude. 
4. With sudden changes in the barometer, the motions of the pendulum 
are relatively very great. 
5. The pendulum does not always oscillate or hang over the same 
point. There is a change in the vertical. 
These results are similar to results obtained by Bertelli, Rossi, and 
other observers in Italy. 
1 Quart. Journ. Geol. Soc. vol. xxxix. 8. 
* See Report, 1881, p. 93; 1882, p. 95. 
P2 
