240 Reports on Special Researches 



Table 13C. Results of Inclination Comparisons at the Hongkong Observatory, 1911. 



'All values referred to station A'; A' = B 0'.6. 



Referring the mean results to I. M. S. (see p. 273), we obtain: 



(13) I. M. S.- Hongkong (Elliott magnetometer No. 55)= + 1'.! (1908^1 1). 

 ( 1 3a) I . M. S. - Hongkong (Elliott magnetometer No. 55) = + 0.00 1 1 9// ( 1 907- 1 1 ). 

 (I3i) I. M. S.- Hongkong (Dover dip circle No. 71, needles 3, 4, 7. 8)= +0'.2 (191 1). 



NO. 14 KEW OBSERVATORY, ENGLAND. 



In the comparisons at the Kew Observatory, the C. I. W. observations by Mr. J. C. 

 Pearson were made on the middle pier of the new absolute house; on several days observa- 

 tions simultaneous with Mr. Pearson's were made by Mr. Baker, of the Observatory, in 

 the old absolute building, about 25 j^ards north of the station occupied by Mr. Pearson. 

 Observing stations were not exchanged, as Dr. Chree, the Superintendent of the Observa- 

 tory, stated that no appreciable differences in the magnetic elements existed between the 

 two points. Consequently the various comparisons are based on the magnetograms, these 

 having been standardized by the observations with the Jones vmifilar magnetometer and 

 the Barrow dip circle of the Observatory. 



The Kew results as given here have been corrected by Dr. Chree for the following 

 sources of error: (a) that arising from assuming the quantity(l +P'r--) = (l+Pr-'^+Qr"^), 

 i. e., assuming that Q is neghgible; (6) that arising from neglecting to take into account the 

 bending of the deflection bar; (c) that arising from error in the accepted value of the 

 moment of inertia. 



The instruments used by Mr. Pearson were: C. I. W. magnetometer No. 5 and Dover 

 dip circle No. 177 (needles 1, 2, 5, and 6). In the interval between the two series of com- 

 parisons, 1908-1910, Mr. Pearson carried out a strenuous campaign of field work in the 

 Turkish Empire, Persia, Asiatic Russia, and Egypt, the same instrumental constants being 

 used throughout. 



