224 



Reports on Special Researches 



NO. 6.-BATAVIA OBSERVATORY. JAVA. 



The following comparisons of the magnetic instruments of the Carnegie Institution of 

 Washington with those of the Imperial Magnetic and Meteorological Observatory of Batavia 

 were obtained in November 1911, when the magnetic-survey vessel, Carnegie, was at 

 Batavia. The observations were all made at night in the absolute pavilion of the Observa- 

 tory, after the electric cars had stopped running. The instruments used by the Obser- 

 vatory were : the reconstructed Meyerstein unifilar for declination, Schulze earth inductor 

 No. 47 for inclination, and Jones magnetometer No. 1 for horizontal intensity. Those used 

 by the observer of the Department of Terrestrial Magnetism, Dr. H. M. W. Edmonds, 

 were: C. I. W. magnetometer No. 4 for decUnation and horizontal intensity, and Toepfer 

 earth inductor (C. I. W. No. 2) for inclination; the results obtained with these instruments 

 were referred to the C. I. W. standards. The observers for the Observatory were: Dr. W. 

 van Bemmelen for declination, Mr. F. R. Rapp for horizontal intensity, and Dr. C. Braak 

 and Mr. J. H. Kats for inclination. 



The dechnations were all obtained on the decUnation pier of the absolute pavilion, one 

 instrument being dismounted while the other was used, the observations with the respec- 

 tive instruments following each other as closely as possible. The observations for hori- 

 zontal intensity were made simultaneously on two piers, namely, the regular horizontal 

 intensity pier of the Observatory, designated in the tables as A, and on the auxiliary pier 

 designated as C; the observers exchanged stations in the middle of the series. Pier A is 

 the northwest pier of the Observatory; pier C being distant from A, 5.75 meters to the 

 south. The inclination observations were made alternately with each earth inductor, 

 on the pier regularly used by the Observatory, the same galvanometer, Plath No. 207, 

 serving for both; one instrument was removed to allow observations with the other, and 

 the series of observations followed one another as quickly as possible. 



Table 6 A. Results of Declination Comparisons at the Baiavia Obsenalory, 1911. 



Local mean time 



Date 



From 



To 



Declination obtained 



C. I. W. Batavia 



Declination reduced 



to scale division 70 



of Wild variation 



unifilar 



C. I. W. Batavia 



C. I. W. -Batavia 



1911 



Nov. 



h m 



19 26 



20 48 

 22 02 

 22 44 

 19 01 



19 22 



20 18 

 20 28 



20 52 



21 03 

 21 41 

 21 57 



h m 



19 42 



20 57 



22 11 



23 00 

 19 18 



19 40 



20 24 

 20 34 



20 58 



21 11 



21 55 



22 14 



+0 47.4 

 47.8 



+0 47.4 



46.9 

 47.2 

 47.1 



47.5 

 48.1 

 47.0 

 46.9 



46.5 

 46.4 



+0.5 (weight 2) 



+0.7 (weight 4) 



Weighted mean value of (C. 1. W. Batavia) . 



+0.6 



The adopted azimuth of the mark used in sighting from the magnetometer pier is 

 171 22'. 7 west of south. As will be noted in the tables, the absolute values obtained by 

 the Observatory have been reduced, in the case of declination and incHnation, to fixed 

 readings of the Wild variometers. The Observatory values of horizontal intensity are all 

 reduced to absolute values for the local mean time of the oscillation-sets; it may be noted, 

 however, that the observations for horizontal intensity for both observers were practically 



