ON COMPARINa AND EEDTJCING MAGNETIC OBSERVATIONS. 65 



parative merits of these various methods. Nevertheless, they are ol 

 opinion that it is highly desirable to record the daily mean values (un- 

 disturbed) of the three magnetic elements side by side with their solar- 

 diurnal variations. 



It will be seen by Appendix III. that Sir J. Henry Lefroy has con- 

 tinued his comparison of the Toronto and Greenwich observations. He 

 has obtained from the smooth curves — that is to say, taking Mr. Wild's 

 method — results which appear to him to show that the turning-point of the 

 declination is decidedly later in local time at Toronto than at Greenwich. 

 Sir J. H. Lefroy attributes this to the fact that these two stations are on 

 different sides of the Atlantic' 



Appendix II. exhibits, by aid of a diagram, an interesting comparison 

 of Senhor Capello between the diarnal variation of the inclination and 

 that of the tension of aqueous vapour. It is remarkable to notice the 

 great similarity between these variations ; a similarity which holds sepa- 

 rately for each month of the year. Senhor Capello hopes that these results 

 may be confirmed by a more extended series of observations. 



The researches to which allusion has now been made refer to the 

 solar-diurnal variation, excluding disturbed observations. With respect 

 to disturbances Sir J. Henry Lefroy has continued his comparison of 

 Toronto and Greenwich, and his results are indicated in Appendix III. 



Professor W. G. Adams has, it is well known, made extensive com- 

 parisons between the simultaneous traces of magnetographs in various 

 places. He is at present engaged on such an undertaking, and the 

 Committee are in hopes that when this is completed he will give them 

 the benefit of his experience. 



Captain Creak and other members of the Committee feel disposed to 

 consider the continuous observation of earth currents an important part 

 of magnetic work. 



The Rev. S. J. Perry and Professor Stewart (Appendix V.) have com- 

 pleted their preliminary comparison of certain simultaneous fluctuations 

 of the declination at Kew and at Stonyhurst in a paper which has been 

 published in the Proceedings of the Royal Society, No. 241, 1885. The 

 results are virtually those which were stated in the last report of the 

 Committee. The comparison is being continued and extended. 



Professor Stewart and Mr. W. Lant Carpenter (Appendix VI.) have 

 given the I'esults of other four years' reduction of Kew declination dis- 

 turbances classified according to the age of the moon. These are very 

 similar to the results of the first four years given in our last report. The 

 same observers give a comparison, extending over four years, between 

 declination disturbances and wind values, which appears to them to show 

 that there is some relation between these two phenomena. They are 

 anxious to continue and extend both these inquiries. 



Professor Stewart has pointed out certain general considerations 

 which appear to him to indicate that the solar-diurnal variation may per- 

 haps be caused by electric currents in the upper atmospheric regions. 

 Dr. Schuster has likewise made a preliminary application of the Gaussian 

 analysis, tending, in his opinion, to confirm the hypothesis that currents 

 in the upper regions are the cause of these variations.^ 



By this analysis Dr. Schuster obtains certain relations between the 



' See Appendix by Sir G. B. Airy to the Greenwich Observations, 1884. 

 ^ An account of these researches will be found in the Phil. Mng., April and May 

 1886. 



1886. V 



