[ 356 ] 



XLVI. Earthquake Observations and Experiments in Japan. 

 By John Milne, F. G.S., and Thomas Gray, B.Sc, F.R.S.E* 



W"E propose to give in this paper a brief rhumi of some 

 experiments on earthquakes performed by us during 

 our residence in Japan. Some parts of Japan, and notably 

 the Yedo plane, where these experiments were made, are sub- 

 ject to very frequent seismic disturbances. It must be borne 

 in mind, however, when considering the experiments and 

 results here described, that the earthquakes which occur in 

 this region are seldom of a destructive character. 



We have found it convenient to divide this paper into two 

 parts. In the first part a very brief discussion of the more 

 important instruments used by us is given; while in the second 

 part some of the most interesting points brought out by the 

 use of these instruments are referred to. 



Part I. 



The instruments may be classified, according to the pur- 

 pose for which they were intended, into the following groups: — 



1. SeismOscopes. 



These are instruments which merely show that an earth- 

 quake has taken place. A great number of instruments of 

 this class have been used ; and descriptions of most of them 

 are to be found in the Transactions of the Seismological 

 Society of Japan. The following are some of the more im- 

 portant : — 



(a) Vessels containing Liquid. — Vessels of liquid have often 

 been referred to in descriptions of earthquakes as giving indi- 

 cations, by the motion of the liquid up the side of the vessel, 

 of the direction and intensity of a shock. In large shocks, 

 provided they can be made to record their motions by some 

 such method as colouring the liquid, or coating the side of the 

 vessel with some substance which can be easily washed off, 

 these may sometimes be of value. For shocks of ordinary 

 intensity we have found them quite useless. Many methods, 

 both mechanical and chemical, were tried; but as yet no prac- 

 ticable method of recording by means of a liquid has been 

 found. 



The chief difficulties are to obtain a liquid which will neither 

 evaporate nor freeze,, and at the same time will not creep up 

 the sides of the vessel. Then, again, it is difficult to get a 



* Communicated bv the Authors. 



