234 



Reports on Special Researches 



The data for No. 2 are those pubhshed on pp. 241-242 of this vohime; those for No. 3 

 are derived by combination of Nos. 1 and 2 and those for No. 4 are the results of Riioker's 

 comparisons in 189.5.' Comparing Nos. 3 and 4 it will be seen that the 1909 Falmouth cor- 

 rections on Kew are for each element numerically smaller than in 1895. There have been no 

 direct comparisons between Kew and Falmouth since those of Rucker, hence it can not be 

 determined, in the absence of other information, when the large improvement in the //-cor- 

 rection occurred and to what it may be due. Mr. L. F. Richardson, the present superin- 

 tendent of Eskdalemuir Observatory, made comparisons at Falmouth the end of June and 

 early in July 1913, but the results are not at present available. 



The data for No. 5 are derived as follows: 



Table IOC. Magnetic elements at the Falmouih Observatory for January I, 1891. 



'The published correction for //, 237, has been algebraicall.v decreased by 67, since it appears that the values of H 

 with the Kew magnetometer, prior to 1908, require to be decreased by this amount on account of various accumulated 

 errors. (Dr. Chree's letter to L. A. Bauer, June 3, 1910.) 



AssembUng the chief results and referring them to I. M. S. (see p. 273), we obtain: 



(10) I. M. S.- Falmouth (Elliott magnetometer No. 66)= O'.O (1909). 

 (10a) I. M. S.- Falmouth (Elliott magnetometer No. 66)= -0.00049// (1909). 

 (lOi) I. M. S.- Falmouth (Dip circle No. 86, needles I and 2)= -0'.8 (1909). 



NO. II. -HAVANA OBSERVATORY. CUBA. 



In the intercomparisons of magnetic instruments at Havana, May 19-23, 1905, two 

 stations were used, viz: C, the absolute observing-house of the Observatorio del Colegio 

 de Bel^n; V, the United States Coast and Geodetic Survey Station of 1903 at the villa 

 Asunci6n de los Jesuitas, located about 3 kilometers south of C. 



The observations were, in general, simultaneous, and the observers exchanged stations 

 during the series. The instruments used by the C. I. W. observer were: U. S. C. and G. S. 

 magnetometer No. 19 and Dover dip circle No. 171. Unfortunately, the Observatory 

 instruments were not at the time in best condition and the constants for the magnetometer 

 (Kew No. 51) had not been recently redetermined; the dip circle had only one needle 

 (No. 1). Accordingly, only the mean results, referred to I. M. S. (see p. 273), are given: 



/. M. S.- Havana {May 1905). 



Declination, 11 sets -|-0'.8. 



Horizontal Intensity, 5 sets 0.00965//. 



Inclination, 6 sets +2'.l. 



The approximate values of the station-difference (C V) were as follows at the time: 

 1'.8 (for decUnation), O'.O (for inclination) and 197 (for horizontal intensity). 



'Report Brit. Assoc. Adv. So. 1896; a correction of 67 was applied to the Kew values according to information 

 supplied by Dr. Chree, June 3, 1910. 



