OX THE JUUTHQUAKE PHKNOMENA OF JAPAN. 249 



are yet required to destroy the vertical motion of earthquakes, .something 

 of practical value will have been done to mitigate the serious results which 

 accompany destructive earthquakes by the elimination of their horizontal 

 movements. 



On the Establishment of an Underground Observatory. 



In December last year I visited the Takashima Colliery, near Nagasaki, 

 with the object of making investigations preparatory to the establishment 

 of an underground observatory. The phenomena which I had the inten- 

 tion of observing were : — 



1. Earth-tremors. — It has been observed that these microscopic move- 

 ments of the soil accompany barometric falls, and it is therefore probable 

 that they may hold some relationship to the escape ot gas which in 

 certain parts of the Takashima mine is a source of considerable danger. 

 At this mine the gas escapes several hours before any marked changes 

 take place in the barometrical column. Should it be found that the 

 occurrence of tremors precedes barometric fluctuations the utility of the 

 observations is obvious. 



The instruments to be used for observation are tromometers, like those 

 employed by Bertelli and Rossi in Italy, and microphones in a telephonic 

 circuit. During my short stay at the mine, I found that a microphone 

 placed in an unworked part of the mine was at times very active. 



2. The observation of delicate levels for the purpose of recording any 

 variations which may take place in the inclination cf the ground. Since 

 I left the mine, Mr. John Stcddart, the chief engineer, who has under- 

 taken these various investigations, writes me that he commenced 

 observations with the levels on the surface of the ground. Owing to a 

 gradual subsidence, due to the underground excavations, which is 

 evidenced by numerous cracks on the surface, the changes in the levels 

 are so great that it will be necessary to establish them underground. 



3. The measurement of the sinking of the underground excavations. 

 As the mine, which is very large, extends a long distance beneath the 

 ocean, it is not unlikely that some connection may be found between the 

 movement of the roof and the tides. Mr. Stoddart tells me that the 

 contrivance for indicating these effects yields such marked results that a 

 number of similar apparatus are being made for distribution in different 

 parts of the workings. 



4. The observation of earth-currents. Whilst I was at the mine, 

 feeble currents were visible on a line only sixty yards in length. 



In consequence of a fire which broke out in the mine shortly after I 

 left, it is only quite recently that Mr. Stoddart has had opportunity to 

 turn his attention to these investigations. At a future period I trust 

 that I may be able to report upon them. For facilities enabling these 

 observations to be made, my thanks are due to the Mitsu Bishi Company, 

 who are the owners of the mine. 



Earth-tremors and Earth-pulsations. 



For the present, the observations on earth-tremors in Tokio have 

 been discontinued. The observations on changes in inclination of the 

 ground, as shown by the movements in the bubbles of levels and in the 

 position of the stile of a pendulum relatively to a point beneath it, are 



