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Special Reports 



with No. 2025 at N and C.I.W. No. 14 at W, but for the one set of observations made 

 on exchange of these stations the Observatory determination was 16 minutes later" 

 than that by C.I.W. No. 14. One set of simultaneous observations for horizontal 

 intensity was made with No. 2025 at N for deflections and at SW for oscillations with 

 C.I.W. No. 14 at W, and one set of simultaneous observations with No. 2025 at W and 

 C. I. W. No. 14 at N. h Schulze earth inductor No. 2 is a fixture on the southeast pier 

 and it was, therefore, not possible to effect an exchange of stations. In view of the 

 incompleteness of simultaneity of observation and exchange of stations it is thought 

 best to base the comparisons upon the magnetograph data, the base-fine values for 

 which were obtained from absolute observations with the Observatory instruments in 

 the absolute observatory at stations as stated in the paragraph above. Dr. Angen- 

 heister states that the station-differences between the 3 piers of the absolute house have 

 been examined and found to be very small. The horizontal intensity at the north pier 

 (N or I) appears to be about 3.5-y greater than at the southwest pier (SW or II) as deter- 

 mined from 6 sets on each pier and noted on page 43 of the publication of the Observa- 

 tory results for 1905-1908; thus, if both oscillation and deflection observations were 

 made at N instead of at SW and N respectively, the Observatory values would be about 

 27 greater. From 6 determinations made in January and February 1916, using Schulze 

 earth inductor No. 2 at N and at SE and using magnetograph data for horizontal and 

 vertical intensity to refer the results to the same times, Dr. Angenheister found that 

 N SE= +0'.3 (regarding dip, south end of needle down, as negative), the probable 

 error of the mean of 6 differences being 0'.16. Dr. Angenheister's judgment is, how- 

 ever, that the station-differences both for horizontal intensity and for inclination may 

 be considered negligible. 



Table 16A. Results of Declination Comparisons at the Samoa Observatory, 1915. 



i All I. M. S. values are referred to JV; N = W+0'.9. 



' The Observatory values are based upon magnetograph data, the base-lino being controlled by 4 sets of declination 

 observations at N during May 16 to 26, 1915. 



" Dr. Angenheister reports, however, that the declination magnetogram shows no change for the interval of 16 minutes. 

 Using only the 2 sets of absolute comparisons in declination referred to, the resulting value for (I. M. S. Samoa) is 3'.6 

 and N=W-j-l'.Q; the corresponding values from 5 determinations referred to the magnetograph (see Table 16A) are 

 (I. M. S Samoa) = -3'.6 and N = W +0'.9. 



b Using only the 2 sets of simultaneous absolute observations in horizontal intensity (I. M. S. Samoa) =+67 or 

 + 0.00017// and N = 17 + 587 against corresponding values of (I. M. S. Samoa) =07 or 0.00U00// and N=W + 52y from 

 3 determinations referred to the magnetograph (see Table 16B), the station-difference for horizontal intensity between N 

 and SW being assumed negligible. 



' Linke, F., und G. Angenheister, Ergebnisse der Arbeiten des Samoa-Observatoriums der koniglichen Gesellschaft 

 der Wissenschaften zu Gottingen. V. Die erdmagnetischen Registrierungen der Jahre 1905 bis 1908, Berlin, 1911. 



