CoMrAKlSONS OF MAGNETIC iStandard.s, 1905-14 



231 



Table 8 C. Resulls nf Indinnlion Comparisons at the Chrislchnrch Observatory, 1006-1908. 

 (Dip circles used by C. I. W. observers: Dover 171 for series I, and 169, 178, and 189 for series II.) 



'There is no appreciable station-difference between west pier absolute house and peg II; in series II, observations were 

 made at 3 different points in the observatory inclosure and at west pier of absolute house, but there are no appreciable station- 

 differences. 



'Simultaneous observations by Mr. H. F. Skey with Dover dip circle No. 147 and needles 1, 2, and 3; station not 

 designated but probably peg II for work on July 10, and west pier of absolute house for work on July 11, 12, and 16, 1906. 



Assembling the chief results and referring them to I. M. S. Csee p. 273), we obtain: 

 (8) I. M. S.-Christchurch (Kew magnetometer No. 1)= + IM (1906-08). 

 (8a) I. M. S.-Christchurch (Kew magnetometer No. 1)= -H 0.00064// (1907-08). 

 (fib) I. M. S.-Christchurch (Dover dip circle No. 147, needles 1, 2, 3)= -0'.9 (1906-08). 



NO. 9. DEHRA DUN OBSERVATORY, INDIA. 



The comparisons at the Dehra Dun Observatory were secured at the conclusion of the 

 magnetic expedition through China in 1909, which was under the leadership of Observer 

 D. C. Sowers. Simultaneous observations were made at both the north {N) and south (.S) 

 absolute houses, the observers exchanging stations as shown in the tables below. The 

 instruments used by the Observatory were: for declination and horizontal intensity, Kew- 

 Elliott magnetometer No. 17, and for inclination, earth inductor No. 30; these instruments 

 are the standards for the Magnetic Survey of India, Dehra Dun being the chief base-station 

 of the Survey. The C. I. W. instruments used were: C. I. W. magnetometer No. 10 and 

 Dover dip circle No. 171 (needles Nos. 5 and 6 of 172, and 7 of 178). 



Some of the intensity results with magnetometer No. 17, not being entirely simul- 

 taneous with the C. I. W. observations, have been referred to the same instant of the latter 

 by use of the magnetograph curves. The Observatory values are corrected fully for both 

 distribution coefficients of the magnets; the value of the moment of inertia of the oscillation 

 magnet and suspension being that determined in September 1909.' 



'Upon the occasion of my visit to the Dehra Dun Observatory on September 29. 1911, Captain Thomas stated that 

 he had under way a reexamination of the moment of inertia for magnetometer No. 17, and that this instrument, the .Survey 

 standard, gives lower values than the other instruments, with the exception of one; the average difference is about 27 gammas. 

 L. A. B. 



