Report of the Kew Committee. 



81 



The following are the values of the ordinates of the various photo- 

 graphic curves : — 



Declination 1 inch = 0° 22''04 1 mm. = 0° 0''87. 

 Bi filar Jan. 4, 1881, for 1 inch c?H=0'0739 foot grain units. 



,, 1 mm. „ =0*00134 mm. mgr. units. 

 ,, Jan. 12, 1881 „ 1 inch „ = 0*0442 foot grain units. 



, 1 mm. „ = 0*00080 mm. mgr. units. 

 Balance Jan. 7, 1881 ,, 1 inch dV =0 0643 foot grain units. 



,, 1 mm. ,, =0*00117 mm. mgr. units. 

 „ Jan. 14, 1881 ,, 1 inch „ =0*0323 foot grain units. 



,, 1 mm. ,, =0*00059 mm. mgr. units. 



Two magnetic storms, or periods of considerable disturbance of the 

 needles, have been registered during the year ; one on the night of 

 January 31st, and a second on September 12th and 13th, both being 

 accompanied by brilliant auroral displays. 



The monthly observations with the absolute instruments have been 

 made regularly, and the results are given in the tables forming 

 Appendix I of this Report. 



Professor W. Grylls Adams has during the year continued his in- 

 vestigations on the comparison of magnetic disturbances in various 

 localities. In addition to the curves mentioned in last year's Report, 

 he has received through the Committee several supplies of copies 

 of selected traces from Mauritius, Toronto, and Zi-Ka-Wei, near 

 Shanghai, as well as from those Observatories already enumerated 

 in the last report. 



Professor Adams has embodied the results of his researches in two 

 papers read before the British Association, and in a Friday evening- 

 lecture delivered at the Royal Institution. 



The discussion of the great magnetic storm of January 31st, 1881, 

 having been undertaken by Dr. H. Wild, of the Central Physical 

 Observatory, St. Petersburg, such particulars respecting that occur- 

 rence as the Committee possessed were transmitted to that gentleman. 



The magnetic instruments have been studied, and a knowledge of 

 their manipulation obtained by Lieutenant Moore, R.N., Dr. Brauner, 

 and Dr. Monckman. 



Information on matters relating to terrestrial magnetism and various 

 data have been supplied to Professor W. G. Adams, Dr. Atkinson, 

 Dr. Buys Ballot, Mr. Gee, Mr. J. E. H. Gordon, Rev. F. Howlett, 

 M. Mascart, Dr. Miiller, Professor Balfour Stewart, and Dr. Wild. 



The following is a summary of the number of magnetic observations 

 made during the year : — 



Determinations of Horizontal Intensity 29 



Dip 160 



Absolute Declination 43 



VOL. XXXIII. G 



