Report of the Kew Observatory Committee. 



97 



I. Magnetic Observations. 



The Magnetographs have been in constant operation throughout 

 the year, and the usual determinations of the Scale Values were made 

 in January. 



The ordinates of the various photographic curves representing 

 Declination, Horizontal Force, and Vertical Force were then found 

 to be as follows : — 



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



Bifilar, January 15, 1896, for 1 inch £H = 0*0280 foot grain units. 



„ 1 cm. „ = 0-00051 C.G.S. units. 

 Balance, January 16, 1896, for 1 inch cV= 0'02 76 foot grain units. 



„ 1 cm. „ = 0-00050 C.G.S. units. 



The magnetic- curves during the past year have been quite free 

 from any very large fluctuations. Some of the principal variations 

 that were recorded took place on the following days : — 



January 3—9, 19—20, 30—31; February "l— 4, 13—14, 28—29; 

 March 4, 26—28 ; April 21—25 ; May 2—3 ; June 16 ; September 

 18 ; October 9 — 12 ; November 7 — 8 ; and December 3 — 4. 



The earthquake of December 17 was shown slightly on the Declina- 

 tion curve, but more distinctly on the Horizontal Force curve, though 

 the disturbance on the latter curve only equalled that due to a change 

 of 0-00004 in the Horizontal Force in the C.G.S. units. 



The hourly means and diurnal inequality of the magnetic elements 

 for 1896, for the quiet days selected by the Astronomer "Royal, will 

 be found in Appendix I. 



The mean values at the noons preceding and succeeding the selected 

 quiet days are also given, but these of course are not employed in 

 calculating the daily means or inequalities. 



The following are the mean results for the entire year : — 



Mean Westerly Declination 17° 10'*8. 



Mean Horizontal Force 018309 C.G.S. units. 



Mean Inclination 67° 22'*3. 



Mean Vertical Force 0-43924 C.G.S. units. 



Observations of Absolute Declination, Horizontal Intensity, and 

 Inclination have been made weekly, as a rule. 



A " Richard " Thermograph has been in constant action in the 

 Magnetograph Room all through the year in order that its res dings 

 may be compared with the observed readings of the Thermometer 

 placed under the Vertical Force shade. 



H 2 



