Comparisons of Magnetic Standards, 1915-21 



405 



Table 2C. Results of Inclination Comparisons at the Cheltenham Observatory, 1915. 



1 Station-differences are negligible. 



used for the C.I.W. observations. The determinations with the two instruments 

 mounted at A and B, were simultaneous. To determine whether any station-difference 

 existed between the piers A and B t) a special, non-magnetic, wooden framework was 

 attached to pier A, and the C.I.W. instrument was placed on this frame as closely as 

 possible to the coil of the Cheltenham inductor. This auxiliary station was designated 

 (EI)'. Since the instruments when mounted on A and on (EI)' could not be operated 

 simultaneously, each complete determination with C. and G. S. No. 26 was made 

 between the two half-determinations with C.I.W. No. 26; the mean values thus apply 

 practically for the same mean times. The results from the observations at A and (EI)' 

 indicate, as in June 1915, that the station-differences between A and ?, and between 

 A and (EI)' are for all practical purposes negligible. The three stations were those 

 occupied in June 1915; the stations A and B, were also occupied for the comparisons 

 during 1908-1913. 



The standard inclination-instrument at the Observatory is, as heretofore, Wild- 

 Edelmann earth inductor No. 26. It has been overhauled, however, and somewhat 

 modified since the comparisons of June 1915, and is now so mounted that the axis of 



1 See Res. Dep. Terr. Mag., Vol. II, pp. 226-228. 



