ON THE EARTHQUAKE AND VOLCANIC PHENOMENA OF JAPAN. 129 



shifted or altered in temperature, changes in magnetic elements may 

 possibly be observed, but, so far as observation and experiment have 

 hitherto gone, we are inclined to the opinion that ordinary earthquakes 

 are in no way connected with magnetic phenomena. 



2. Electric Phenomena. 



In the Report for last year I gave the results of a comparison of the 

 records of several hundreds of earthquakes, and the photographic records 

 of atmospheric electricity from a Mascart electrometer. The observations 

 were made at the Meteorological Observatory in Tokio. A result arrived 

 at was that at the time of many earthquakes, especially when Tokio was 

 rear the epicentrum, the air often became electro-negative. In a detailed 

 paper on this same subject (' Trans. Seis. Soc.,' vol. xv. p. 160) it is 

 stated that these results ' must only be regarded as tentative,' and as 

 during the past year I have discovered a source of error in Mascart's 

 instrument, this remark must not be overlooked. Sometimes, even in 

 exceedingly dry weather, the instrument rapidly loses its sensitiveness, 

 and, if the mirror be displaced, it does not quickly return to zero. The 

 reason does not appear to reside in the fibre nor always in the acid, for, 

 if the wire dipping in the acid and attached to the needle and mirror be 

 taken out and washed, the sensitiveness is regained. Now the acid is 

 being changed weekly and the wire washed. The results which have 

 already been recorded having an explanation in mechanical movements 

 must still be regarded as tentative. 



Second Report of the Committee, consisting of Lord Rayleigh, 

 Sir William Thomson, Professor Cayley, Professor B. Price, 

 Dr. J. W. L. Glaisher, Professor A. Gr. GtREENHILL, Professor 

 W. M. Hicks, and Professor A. Lodge (Secretary), appointed 

 for the purpose of calcidating Tables of certain Mathematical 

 Functions, and, if necessary, of taking steps to carry out the 

 Calculations, and to publish the results in an accessible form. 



The first Report was in 1889. Since then values of 1q{x) have been 

 ■calculated from a'=0 to a;=6'10 at intervals of 'Ol, and considerable pro- 

 gress has been made in still further expanding this table, making the 

 interval -001. This will enable values of Io(a;) for intermediate values 

 of X to be read off by the help of first differences only. 



Progress has been made towards the calculations cf Ii(aO for values 

 of X differing by the interval -01, or, if desired, -001. The method 

 adopted is that of calculating the successive differential coefficients of 

 I) (a;) for the values of x given in the 1889 Report by means of the 

 formula 



and its derivatives, and interpolating by means of Taylor's Theorem. 



The Committee have asked for a grant of 15L, to enable them to 

 employ a professional calculator to help in the continuation of the work. 



1891. K 



