408 Special Reports 



NO. 3. CHRISTCHURCH OBSERVATORY, NEW ZEALAND. 



Series I, III, and V of comparisons at the Christchurch Observatory in November 

 1915, in April 1916, and in October to November 1920, were obtained during the visits 

 of the magnetic-survey vessel Carnegie to Port Lyttelton, Messrs. H. M. W. Edmonds 

 and I. A. Luke observing for series I and III, and Messrs. H. F. Johnston and H. R. 

 Grummann observing for series V, with the C. I. W. instruments; series II was obtained 

 in December 1915 by Observer H. E. Sawyer; series IV was obtained during February, 

 April, and May 1916 by Observer W. C. Parkinson. Simultaneous observations with 

 the Observatory absolute-instruments were made only for series I and V, for inclination 

 comparisons of May 1916 in series IV, Director H. F. Skey observing throughout. 

 Four stations were used, viz, the east and west piers of the absolute house and the 

 stations designated by the Observatory authorities as jarrah peg and brass pipe. These 

 were the stations occupied for the comparisons during 1906-1908, the station jarrah 

 peg being the same as the station previously designated peg A. The east pier in the 

 absolute house is used regularly for the Observatory absolute-observations of declination 

 and horizontal intensity while the west pier in the absolute house is used regularly for 

 the Observatory absolute-observations of inclination. There is a small wooden pier to 

 the north of west pier, on which the galvanometer is mounted. The station jarrah 

 peg is 12.14 meters and 14.10 meters from the northeast and northwest corners of the 

 absolute house respectively. The station brass pipe is 21.70 meters north of east from 

 the station jarrah peg. The azimuth mark, designated Rmi, used for the east pier was 

 a piece of wood covered with white cloth in a 2-inch iron pipe to the east of north of 

 the west end of a small lake known as Victoria Lake; its true bearing from east pier 

 is 196 09'.0 west of south and from jarrah peg is 196 03'. 8 west of south. A similar 

 mark, designated Rm 2 , on the south bank of the west end of Victoria Lake was used 

 for the station jarrah peg; its true bearing from that station is 200 13'. 3 west of south. 

 The mark R?n 2 was also used for the station brass pipe; its true bearing from that station 

 is 195 14'.2 west of south. The true bearings were supplied by Director Skey. 



The Observatory absolute-instruments used for series I and V were magnetometer 

 No. 1, manufactured by the Cambridge Scientific Instrument Company, for declination 

 and horizontal intensity, and earth inductor No. 109, manufactured by Toepfer and 

 Son, for inclination. The Christchurch values for series II and III depend upon the 

 magnetograph data which in turn are based upon absolute observations made with 

 the above instruments at the stations regularly used by the Observatory. The C. I. W. 

 instruments used were magnetometer No. 5 and magnetometer-inductor No. 25 for 

 series I, III, and V, magnetometer No. 17 and Dover dip circle No. 223 with needles 

 1, 3, 5, and 6 for series II, universal magnetometer No. 14 with needles 1, 2, 5, and 6, 

 and dip circle No. 201 with needles IX, 2X, 3X, and 4X for series IV. The corrections 

 on International Magnetic Standards 6 applied to results obtained with the C.I.W. 

 instruments were those finally adopted. Some observations were also made during 

 series I and III with C.I.W. marine inductor No. 3; the results, however, were not 

 utilized since this instrument was then, because of wear arising from long use on board 

 ship, less satisfactory for land work than the inductor attachment of magnetometer- 

 inductor No. 25. 



All the observations were interfered with to some extent by disturbances caused 

 by electric-tram lines. There is a tramway about one-quarter mile west of south of 

 the Observatory which has comparatively infrequent service, another about one-half 



" See Res. Dep. Terr. Mag., Vol. II, pp. 229-231. 

 6 See Res. Dep. Terr. Mag., Vol. II, pp. 270-278. 



