270 



Reports on Special Researches 



Table 31 B. PreUmiuary fiesulls of Comparisons between the Potsdam Magnetic Standards and Certain Observatory 



Standards. 



[This series of comparisons was made by Dr. W. Kiihl, of the Potsdam Magnetic Observatory, in 1910, and referred by him 

 to the Potsdam magnetic standards (Wanschaff magnetometer and Schulze earth inductor No. 1). His preliminary 

 results as published^ arc given in the table below; AD has the sign attached assuming east declination to be positive and 

 the AH quantities have been expressed in parts of H.] 



'Kuhl, W. Vergleichung der Hauptbarometer und der magnetische absoluten Instrumente in de Bilt, Paris Val 

 Joyeux und Pawlow.sk mit denea in Berlin Potsdam. Berlin, Veroff. Met. Inst., No. 229, 1911, pp. 150-159. 

 -The declinations are observed with a special declinometer. 



^The correction for the new earth inductor at de Bilt, on Potsdam, is given provisionally as 3'. 

 "The declination result depends upon a single observation by Dr. Kuhl. 

 'Magnets I and II. 

 *The correction for the Val Joyeux dip circle, on Potsdam, was -{-V.S. 



By means of the following table (31 C) it becomes possible to refer, approximately, 

 the preliminary results of the comparisons given in Tables 31 A and 31B to the Inter- 

 national Magnetic Standards (I. M. S.; see p. 273). This table has been derived with the 

 aid of the C. I. W. comparisons (Table A, p. 278), the Russian comparisons (Table 31 A) 

 of 1907-08, and the German comparisons (Table 31 B) of 1910. The two observatories 

 common to the three series of comparisons are Kew and Potsdam. We, accordingly, have 

 the relations shown in Table 31 C. Applying the relation (7) in this table to the Russian 

 series (Table 31 A), and that given by (2) to the German series (Table 31 B), Table B, p. 278, 

 is finally derived. 



Table 31 C. Determining the relationship between Die International Magnetic Standards and the Pavlovsk StaTidards. 



'According to Dubinsky and Kuhl, half-weight being given to the latter's results, as he wishes them regartled as 

 provisional ones. 



REDUCTION TO INTERNATIONAL MAGNETIC STANDARDS. 



Thus far in the tables giving the results of C. I. W. comparisons between various mag- 

 netic instruments, all fjuantities obtained have been referred to the same standards, which 

 have been designated a.s the "G. I. W. Standards." Before making a final .summary of the 

 results, it will be desii-able to see what corrections may be applied safely to the C. I. ^^^ 

 standards in order to refer them, as nearly as may be practicable at present, to world or 

 international magnetic standards, to be designated as "I. JVI. S." 



In the absence of any agreement among nations as to such international standards, 

 it was necessary for the Department of Terrestrial Magnetism to adopt at the very begin- 



