COMPARISONS OF MAGNETIC STANDARDS, 1915-21 



473 



III. Series of Comparisons During 18C8 and 1902 by Professor Palazzo. 



From Professor Palazzo's final values" (see p. 451) for the results of the C. I.W. 

 comparisons with his instruments in 1911 and 1913, we may obtain, through his excel- 

 lent series of comparisons in 1898 and 1902, the corrections on I. M.S. for the observa- 

 tories at Pare St. Maur and Kew in 1898 and at Potsdam and Pola in 1902. Professor 

 Palazzo used the same instruments for all comparison observations, viz, Dover magnet- 

 ometer No. 122 and Dover dip circle No. 51 with needles 1 and 2. The observed data 

 and resulting corrections on I. M.S. for Kew, Pola, and Potsdam, as presented in Table 

 21B, show substantial agreement with the values obtained directly at these observatories. 

 This is particularly the case for Kew indicating for that observatory an excellent con- 

 stancy of standards from 1898 to 1919 in declination and inclination and from 1898 to 

 1910 in intensity (see p. 441). Therefore we may expect the resulting values as given 

 in Table 21B for (I. M.S. -Pare St. Maur) to be good. 



Table 21B. Comparisons on I. M. S. Resulting Indirectly from Comparisons between Rome Magnetic Standards 



and Certain Observatory Standards. 



[The results published in Professor Palazzo's report have been modified here as follows: (a) the signs of the declination 

 differences (aD) have been reversed in order to correspond with east declination taken as positive.] 



i The values given depend upon number of sets as follows: aD, twelve at each observatory except Kew wheie eight 

 only; AH, two at each observatory (a set consisting of two sets of oscillations and two sets of deflections at two distances) : 

 Al, two at each observatory (a set with dip eiicle No. 51 consisting of the mean by the four needles 1, 2, 5, and 6). 



These data, except where given in Professor Palazzo's reports, taken from publication of each observatory for year 

 concerned. 



" The values of resulting (I. M. S Observatory) for Bamberg magnetometer 7904 are obtained by means of the pub- 

 lished differences given by the Year Book of the Pola Observatory for 1903 (pages XXXIX-XLII), viz: [Pola (Bamberg 

 No. 7904) Pola (Schneider)] = -0'.57 (6 sets, January 1903), and [Pola (Bamberg No. 7904) Pola (Schneider)] = - 

 0.00046H (6 sets, December 1902). 



The resulting values in Table 21 A for (I. M. S.- Observatory) afford further evi- 

 dence of some change in the intensity standard at Kew after 1910 (see p. 441) ; the values 

 for AD and for Al are in excellent agreement with the direct determinations. There is 

 also indication of a change in intensity standard at Greenwich and in the same direction 

 as indicated by the two series in 1915 and 1919 (see pp. 423-426). Except for Falmouth 

 and Kew the values of AD do not show good agreement with other values. At Val 

 Joyeux magnetometer Chasselon No. 37 is the medium-size model after the design of 

 the large Brunner instrument used at Pare St. Maur and is presumably the same as the 

 instrument designated "Moureaux" in the 1910 comparisons by Kubl. 4 The corrections 

 obtained for the Val Joyeux dip circle disagree. A third value may be obtained from 

 Kurd's comparisons at Val Joyeux in 1910; he found the relation between the earth in- 

 ductor and the dip circle to be 



Earth inductor No. 61 =Val Joyeux dip circle+2'.O 



" Palazzo, L.Misuremagneticheeconfrontimagnetometrici aTerracina. Ann. dell Uff. Centra. eGeod.. vol.37, 1920. 



6 Kiihl, W. Vergleichung der Hauptbarometer und der magnetische absoluten Instrumente in de Bilt, Paris Val 

 Joyeux, und Pawlowsk mit denen in Berlin-Potsdam. Berlin, Veroff. Met. Inst., No. 229, 1911, pp. 150-159. Cf. also 

 lies. Dcp. Terr. Mag., Vol. II, p. 270. 



