212 



Report of the Keiv Committee. 



was found necessary to re-adjust the instrument by altering slightly 

 the inclination of the mirror attached to the magnet. 



The values of the ordinates of the different photographic curves 

 determined then were as follows : — 



Declination : 1 inch=0° 22''04. 1 cm. = 0° 8'7. 



Bifilar, January 10, 1887, for 1 inch £H=0'0255 foot grain unit. 



„ 1 cm. „ =0-00046 O.G.S. unit. 

 Balance, January 11, 1887 ,, 1 inch <)V=0'0281 foot grain unit. 



„ 1 cm. „ =0-00051 C.G.S. unit. 



In the case of the bifilar magnetometer it was also found necessary 

 to re-adjust the instrument, at the same time its sensibility was 

 slightly altered, after which the scale value was again determined 

 with the following result : — 



Bifilar, January 18, 1887, for 1 inch SH = 0-0280 foot grain unit. 



., 1 cm. „ =0-00051 C.G.S. unit. 



With regard to magnetic disturbances, no very exceptioual move- 

 ments have been registered during the year. 



The principal oscillations, however, were recorded on the following 

 dates : November 2 to 6, 1886 ; February 13 and 14, April 5 to 7, 

 August 2, and September 26 and 27, 1887. Much interest was 

 evinced in the curve for February 23, which registered the occurrence 

 of an earthquake. 



In February last new adjusting screws were fitted to one of the 

 microscopes attached to the Kew dip-circle ~No. 33. 



Information on matters relating to terrestrial magnetism and 

 various data have been supplied to Professor Mascart, Professor 

 Adams, Dr. Atkinson, Professor Schering, Dr. Rijckevorsel, and 

 Messrs. Archbutt and Stanley. 



Professors Riicker and Thorpe visited the Observatory in January 

 last, and made a series of base observations, prior to their departure 

 for Ireland to finish their magnetic survey of the British Isles, which 

 was commenced in 1883. On returning to England a further series 

 of observations were made at Kew in October in order to complete 

 the survey. 



The monthly observations with the absolute instruments have been 

 made as usual, and the results are given in the tables forming- 

 Appendix I of this Report. 



The following is a summary of the number of magnetic observations 

 made during the year : — 



Determinations of Horizontal Intensity 28 



,, Inclination 110 



„ Absolute Declination 40 



