DEPARTMENT OF TERRESTRIAL MAGNETISM. 



257 



respectively. The C. I. W. magnetometers used for these observations were 

 compared both before and after field use with the standard instruments at 

 Washington. Thus there is obtained indirectly a comparison between the 



Table 1. — Horizontal-intensity comparisons at Washington, 1931 and 1923, between prO' 

 visionally adopted International Magnetic Standard and sine galvanometer. 



o The weights are assigned according to the number of sets, number of days on which observa- 

 tions were made, and magnetic conditions. 



b The small weight assigned is because the station-difference involved depends upon exchange 

 of magnetometers only. 



Table 2. — Summary of horizontal-4ntensity comparisons between provisional International 

 Magnetic Standard of Carnegie Institution of Washington and electric magnetometers, 

 August 1922 to March 1923." 



" The table is to be read thus, for example, first row: 



SG-IMS = -[-0.00007//; SS-IMS = +0.00015//; W-IMS = +0.00040//. 



* This provisional standard was adopted in 1914 (see Res. Dept. Terr. Mag., vol. 11, 270-279 

 (1915). 



^ This value is subject to correction for any station-difference which may be found between 

 the two observing piers used at Teddington, England, for the comparisons in September 1922. 



