416 REPOKT— 1886. 



future report. In the report written last year some reference was made 

 to the experiments in a pit. For a strong earthquake I showed that the 

 motion at the bottom of the pit (which is ten feet in depth) was very 

 much smaller than the motion on the surface. For very small earthquakes 

 this distinction is not so marked ; the only difference between the move- 

 ment below and that above is that the former has a longer period. 



Among the earthquakes which have occurred during the last few 

 months several have been felt as short sharp bumps. On these occasions 

 I have repeatedly noticed that a lamp hanging in the centre of my room 

 acquires a rapid vibratory vertical movement, and there has been no per- 

 ceptible swing. My impression with regard to these shocks, which are 

 usually very short, is that they have an origin immediately beneath Tokio, 

 The vertical motion of the disturbances we feel in Tokio is relatively to 

 the horizontal motion extremely small, seldom exceeding the fraction of a 

 millimeter. So far as I am aware, it has never exceeded two or three 

 millimeters, and the general rule is that vertical movement is but rarely 

 recorded. 



In addition to the short sudden vertical movements, we have had 

 others which have been characterised by their length and the slowness of 

 their pei'iod. Such a disturbance occurred a few days before I left Tokio. 

 At the time I was sitting at a table upstairs, when I fancied that I felt a 

 movement. On looking up I saw that my lamp was swinging back and 

 forth through a considerable arc. A disturbance of this kind would 

 hardly be recognised as an earthquake by a person who had not been in 

 the habit of recording such phenomena. 



III. The Earthquakes of 1885-1886. 



In my fourth report to the British Association I gave, in an epito- 

 mised form, the results obtained by the observation of 387 earthquakes 

 which had occurred between October 1881 and October 1883 in North 

 Japan. A complete account of this work has now been published by the 

 Seismological Society as Vol. VII. Part II. of their Transactions, Similar 

 work, but extended to embrace the whole of the empire, has been under- 

 taken by the Meteorological Department of this country, and results of a 

 valuable nature have already been obtained. As this work is a continua- 

 tion of that which has already been brought to the notice of the British 

 Association, and as I have from time to time been consulted as to how it 

 should be carried out, a brief account of the more important results which 

 have been obtained may not be out of place. Professor K. Sekiya, who 

 now holds the chair of seismology in the Imperial University of Japan, 

 and who has had the immediate superintendence of these observations, 

 will give a translation and fuller account of this work to the Transactions 

 of the Seismological Society. 



The observations were made with the assistance of bundles of post- 

 cards distributed with observers at 600 stations situated in various 

 parts of the empire. During the year 1885 records were received at the 

 Meteorological Department which formed the foundation for a series of 

 maps showing the areas shaken by 482 distinct disturbances. 



On the average there were, therefore, 40 earthquakes per month, or 

 1"3 per day. 



The distribution of these disturbances according to months and 

 seasons is shown in the following tables : — 



