Comparisons of Magnetic Standards, 1915-21 



437 



Table 10A. Results of Declination Comparisons at the Kew Observatory, 1915. 



Seri 



Declination obtained 



I M. S. 



15 22.5 

 22.1 



20.5 

 19.8 

 19.8 

 19.6 

 24.9 

 24.7 

 23.9 

 23.1 

 21.1 

 20.7 

 16.0 

 23.5 

 24.7 

 24.5 



23.5 

 26.1 



Kew 



15 22.6 

 22.4 

 20.6 

 20.0 

 19.8 

 19.6 

 25.0 

 24.7 

 23.9 

 23.4 

 21.6 

 20.8 

 16.4 

 23.5 

 24.5 

 24.4 



23.6 



25.6 



Mean . 



II 



-15 20.3 

 20.0 

 19.9 

 19.9 

 19.0 

 18.1' 

 21.7 

 21.9 

 21.2 

 20.1 

 19.7 



18.8 

 Mean 



Mean value of (I. M. S. Kew) from I and II. 



15 20.2 

 19.9 

 19.9 

 19.6 

 19.0 

 18.5 

 21.5 

 21.6 

 21.0 

 20.2 

 19.2 

 18.6 



I. M. S.- 

 Kew 



+0.1 



+0.3 



+0.1 



+ 0.2 



0.0 



0.0 



+0.1 



0.0 



0.0 



+0.3 



+0.5 



+0.1 



+0.4 



0.0 



-0.2 



-0.1 



+0. 

 -0. 



+ 0.08 



-0.1 

 -0.1 



0.0 

 -0.3 



0.0 



-0.2 

 -0.3 

 -0.2 

 -0.1 

 -0.5 

 -0.2 



-0.16 



0.0 



Remarks 



C. I. W. magnetomoter No. 26 at 

 ' Nm', Kew Jones magnetometer at 

 0. 



C. I. W. magnetometer No. 26 at 

 O m ; Kew Jones magnetometer at 



Nm. 



C. I. W. magnetometer No. 26 at 

 1 0,; Kew values from magneto- 

 grams. 



I C. I. W. magnetometer No. 26 at 

 \ N m \ Kew values from magneto- 

 grams. 



C. I. W. magnetometer No. 26 at 

 N m ; Kew Jones magnetometer at 

 O m . 



C. I. W. magnetometer No. 26 at 

 Om\ Kew Jones magnetometer at 

 N n . 



1 This observation is rejected because magnet 26L was inadvertently rotated in its stirrup 90 from its proper position. 



standard instrument at Hongkong, and Elliott No. 83 gave from 4 determinations 

 made in December 1916 (using a home-made variometer to reduce to a common reading), 

 according to Director Claxton's letter of January 19, 1917, 



(b) Hongkong No. 83 Hongkong standard No. 55 = +22 7 (at Hongkong) = +0.00059//. 

 Hence from (a) and (b) we have: 



(c) Kew Hongkong No. 55 = +0.00178//, 



From the compilation of comparisons at Hongkong Observatory (see p. 431) we have 

 (</) I. M. S. Hongkong No. 55 = +0.00109//, 



whence: 



(e) I. M. S. Kew = -0.0007//. 



A second indirect check is to be had through comparisons at Kew during October 

 and November 1914 of Cooke magnetometer No. 40 purchased by the United States 

 Coast and Geodetic Survey and subsequently compared at Cheltenham Observatory. 

 The comparisons (6 sets) during October and November 1914 at Kew, when referred 



