Comparisons of Magnetic Standards, 1915-21 



439 



Table IOC. Results of Inclination Comparisons at the Kew Observatory, 1915. 



' Times given apply to C. I. W. observations (see foot-note 2). 



= The Kew values were derived from the horizontal-intensity and vertical-intensity magnetograms allowance being 

 made for the departures from the mean values of the horizontal intensity and of the vertical intensity corresponding to the 

 observed inclinations determined on each day, as indicated in the column of remarks, by Dr. Chree with the Kew dip circle 

 No. 33. 



parisons with interchange of stations could not be obtained except for the inclination 

 work, the declination and horizontal-intensity comparisons depending upon rnagnet- 

 ograph data. The C. I. W. stations were all in the new absolute house, the east pier, 

 N e , and west pier, N w , being used for the inclination observations, and the center pier, 

 N m , being used for the declination and horizontal-intensity observations; N e was not 

 occupied in the two series of 1915. The azimuth mark used was, as in 1915, the obelisk 

 in the Park; its true bearing, as supplied by Dr. Chree, being 182 06'.3 west of south. 

 Dr. Chree stated that tests showed there was no sensible station-difference between the 

 piers of the new and old absolute houses. 



The absolute instruments of the Observatory were as for the two series in 1915; 

 the simultaneous inclination observations with the Observatory Barrow dip circle were 

 made by Dr. Chree. The C. I. W. instruments were magnetometer No. 13 and dip 

 circle No. 177 with needles 13X and 16X (needles 14X and 15X were also used on April 

 1 in tests to select the better pair for use in the comparisons). The corrections on 

 International Magnetic Standards" applied to the C. I. W. results are those tentatively 

 adopted (see pp. 10 and 15) pending return and ^standardization at Washington, 

 probably sometime in 1922. 



".See Res. Dcp. Terr. Mag., Vol. II, pp. 270-278. 



