Comparisons of Magnetic Standards, 1915-21 451 



(146) I. M. S.-Rio de Janeiro (Cooke magnetometer No. 25) = 0'.0 (1915-1919). 



(14c) I. M. S.-Rio de Janeiro (Cooke magnetometer No. 25) = -0.0034// (1915-1919). 



(I4</) I. M. S.-Rio de Janeiro (Dip circle No. 8075, needles 1 and 2)= -0'.7 (1915). 



(I4e) I. M. S.-Rio de Janeiro (Dip circle No. 221, 3 needles a ) = -0'.7 (1919). 



NO. 15. ROME OBSERVATORY, ITALY. 



Since the publication of results 6 obtained in 1911 and in 1913 from the comparisons 

 of the magnetic instruments of the Ufficio Centrale di Meteorologia e Geodinamica at 

 Rome, Professor Palazzo" has reported some small changes in the data originally given 

 for his instruments. Because of improved values for azimuths of marks used and 

 because of slight modifications in computations of horizontal intensity the mean results 

 referred to I. M. S. become: 



(15) I. M. S.-Rome (Dover magnetometer No. 122)= -0'.3 (191 1-1913). 

 (15a) I. M. S.-Rome (Dover magnetometer No. 122) = +0.00025// (191 1-1913). 

 (15c) I.M. S.-Rome (Dover dip circle No. 51, needles 1,2, 5, 6)= -0'.4 (191 1-1913). 



NO. 16. SAMOA OBSERVATORY, AT APIA, UPOLU. 

 Series I, 1915. 



The comparisons of May 1915 with the Samoa Geophysical Observatory at Apia, 

 Upolu, Samoan Islands, were carried out by Dr. G. Angenheister for the Observatory and 

 by Mr. W. C. Parkinson for the Department of Terrestrial Magnetism. The Observa- 

 tory instruments were "Stations-theodolith" Tesdorpf magnetometer No. 2025 (magnet 

 12 for declination and magnets 12 and 38 for horizontal intensity) and Schulze earth 

 inductor No. 2; the Department instrument was universal magnetometer C.I.W. No. 14 

 (magnet 14L for declination, magnets 14L and 14S for horizontal intensity, and needles 

 1, 2, 5, and 6 of No. 14 for inclination). The constants for Tesdorpf No. 2025 in hor- 

 izontal intensity depend on standardizations made at the Potsdam Observatory; pro- 

 vided no change has taken place since these standardizations, the Samoa Observatory 

 standard in horizontal intensity should be the same as that at Potsdam. For declination 

 and inclination the observed values by the Observatory instruments are accepted 

 without correction. The corrections on International Magnetic Standards for universal 

 magnetometer C. I. W. No. 14 were as finally adopted. 



The Observatory absolute observations were made on 4 piers, viz, north pier, 

 designated A'', of absolute observatory used for declination and deflection observations; 

 southwest pier, designated SW, of absolute observatory used for oscillation observations; 

 southeast pier, designated SE, of absolute observatory used for inclination observations; 

 and west pier, designated W, outside of the absolute observatory for declination and 

 horizontal intensity. W is 15 meters south 99 04' west of and about y$ meter lower 

 than A''. The C.I.W. observations for the 3 elements were made at stations N and W. 

 The mark and azimuths adopted in the reductions are those used by the Observatory, 

 viz, Tuamua Church, distant from W 3250 meters, azimuth from W south 96 10'. 1 

 west/ azimuth from AT south 96 10'.9 west. 



It was not possible to effect complete simultaneous absolute observations with 

 exchange of stations. One set of simultaneous observations for declination was made 



Needles 1 and 2 of 221, and 2 of No. 8075. 



6 See Res. Dep. Terr. Mag., Vol. II, pp. 254-256. 



c Palazzo, L., Misure magnetiche e confront! magnetometrici a Terracina, Ann. dell Uff. Centra. Meteor, e Geod., Vol. 

 37, 1920. 



d Mr. Parkinson's determination from morning and afternoon Sun observations gives the value from W south 96 

 09'.0 west; the corresponding value from N would be south 96 09' .8 west. 



