Comparisons of Magnetic Standards, 1915-21 



461 



Assembling the results we have: 



(18) I. M. S. Tananarive (Brunner magnetometer) = +5'. 4 (1920). 

 (18a) I. M. S. Tananarive (Brunner magnetometer) = -0.0037// (1920). 

 (186) I. M.S. -Tananarive (Brunner dip circle) =+4'. 5 (1920). 



NO. 19. WATHEROO OBSERVATORY, WESTERN AUSTRALIA. 



The comparisons in September 1920 at the Watheroo Observatory of the Carnegie 

 Institution of Washington were secured by the Carnegie party during the vessel's visit 

 at Fremantle. Messrs. J. P. Ault, H. R. Grummann, and A. Thomson made the obser- 

 vations with the Carnegie instruments and Messrs. E. Kidson and W. C. Parkinson 

 those with the Observatory instruments. The stations used were the piers N m and S m 

 for declination and horizontal intensity and the piers N w and S w for inclination in the 

 absolute house of the Observatory; piers N m and S m are on center line along the length 

 of the absolute house near north and south ends respectively, while piers N w and S w 

 are each 4 feet (1.22 meters) west of piers A 7 and *S m ; the distance between N and S piers 

 is 25 feet (7.62 meters). The Observatory azimuth-marks were used, the azimuths as 

 supplied by Mr. Kidson, observer-in-charge, being from N m , 265 06'. 6 west of south, 

 and from S m , 263 35'.9 west of south. 



The Observatory instruments used in these comparisons were C. I. W. magnetometer 

 No. 7 with correction on standard of 0'.2 in declination (reckoning east declination 

 as positive) and of 0. 0005477 in horizontal intensity, and C.I.W. earth-inductor No. 2 

 with zero correction on standard. The Carnegie instruments were C. I. W. magnetometer 

 No. 5 and C.I.W. marine earth-inductor No. 7. Throughout, the method of compari- 

 sons by simultaneous observations was employed, the observers exchanging stations to 

 eliminate the station-differences. The corrections on I. M.S. for the Carnegie's instru- 

 ments were those finally adopted. 



The standards of the Observatory are the provisional International Magnetic 

 Standards of the Department, and the results of the comparisons show that the correc- 

 tions adopted when the instruments were last calibrated at Washington in April and 

 May 1916 have been maintained practically unchanged. 



All values are refened to N m ; A r m = S m + 0'.4. 



