Report of the Kew Committee. 



153 



In accordance with the usual practice, determinations of the scale 

 values of all the instruments were made in January last, and the 

 ordinates for the different photographic curves were then found to be 

 as follows : — 



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



Bifilar, January 7, 1891, for 1 inch BR = O0277 foot grain unit. 



„ 1 cm. „ = 0-00050 C.G.S. unit. 

 Balance, January 8, 1891, for 1 inch cV= 0275 foot grain unit. 



„ 1 cm. „ = 0-00050 C.G.S. unit. 



The following are the principal results of the Magnetic Elements for 

 the years 1890 and 1891 :— 



Mean Westerly Declination . . 1890 . . 17 50-6 

 „ 1891 . . 17 41-9 



Mean Horizontal Force 1890 . . 0-18173 C.G.S. unit. 



1891 .. 0-18193 



Mean Dip 1890 .. 67 32 5 



1891 31-2 



Mean Vertical Force 1891 . . 0*43962 C.G.S. unit. 



Additional observations of the Horizontal Force, Inclination, and 

 Declination have been made each month with the absolute instru- 

 ments for the purpose of determining with greater precision the zero 

 values of the magnetograph curves. 



Information on matters relating to terrestrial magnetism and 

 various data have been supplied to Professors Thorpe and Riicker, 

 Dr. Yan Rijckevorsel, Captain Schuck, and Professor Stroud. 



In January the Kew 9-inch unifilar, by Jones, was sent to Messrs. 

 Elliot Brothers for cleaning, and, at the same time, certain alterations 

 were introduced in order to modernise the instrument. Unfortu- 

 nately, the heavy brass telescope support was found on examination 

 to be slightly magnetic, and it was therefore discarded, and, on Feb- 

 ruary 12, the magnetometer was restored to its original state, with the 

 exception of a brass tie-piece, which, being found non-magnetic, was 

 retained until the end of the year. 



On closely discussing the Declination observations of the preceding 

 years it was found that observations given with the old collimator 

 magnet N.E. were more subject to a variable torsion effect than were 

 those of the collimator marked K.O. 90. The two having been em- 

 ployed in conjunction for one year, it was decided, with the com- 

 mencement of 1891, to discard altogether the use of the old heavy 

 magnet for the purpose of observing Declination. 



m 2 



