Reductions to Standard Instruments 



43 



A. Results of Direct Comparisons 



Potsdam . . . 



Kew 



Po!a 



Toronto. . . . 



Tiflis 



Cheltenham' 

 Zi-ka-wci . . . 

 Dehra Dun. 

 Helwan. . . . 

 Havana. . . . 

 Hongkong. . 



Alibag 



Samoa 



Pilar 



Melbourne. . 

 Christ church 



Feb. 1910 



Mar. 1908, Mar. 1910 



Feb. 1910 



Sep. and Oct. 1906 by Dept.; Oct. to 



Nov. 1909, and Apr., Sep., and Oct. 



1910 by Meteorological Ser\'ice 

 June 1908* 



Feb. and Mar. 1908, and Mar. 1910 

 May and gep. 1907 

 Oct. 1909 

 Apr. 1908 

 May 1905 

 Dec. 1908 for D and H, and Mar. 1911 



fori 

 Mar. 1911 

 May 1906 for D and H, and May and 



Dec. 1906 for I 

 Jan. to Feb. 1911 

 Nov. 1906 

 July 1906 and Dec. 1907 to Jan. 1908 in 



D and I; Dec. 1907 to Jan. 1908 for H 



B. Results of Indirect Comparisons' 



'This difference in / at Toronto is as based on the old observatory standard, viz., Dover circle 130, needles 

 1 and 2, since superseded by Dover circle 200, needles 1 and 2, for which the Department has as yet no data. 



' This difference in H at Toronto is as based on the new observatory standard, Elliott magnetometer 98, and 

 constants adopted in Februarj', 1911. 



Possible local artificial disturbance during this work. Compare the results obtained for Tiflis with the indirect 

 comparison of December, 1907. 



The observatory results for the comparisons of June and July, 1909, are not yet available. 



' The standards for the United States Coast and Geodetic Survey observatories at Sitka, Baldwin, Honolulu, 

 and Vieques, are identical with those at Cheltenham. The same remark applies for the new observatory at Tucson, 

 which succeeded the Baldwin Observatory, discontinued in October, 1909. 



This is on the basis of the value of tt'K of September, 1909, for the observatory standard magnetometer. 

 ' Referred to magnetometer 83 at Hongkong, AH would be +0.0008//. 



' Determined from reports of intercomparisons of Dubinsky and Kiihl and Department obser\'ations at Kew 

 and Potsdam. 



' The difference in inclination for observatory earth inductor, Schulze 61, is 0'.5. 



