Comparisons of Magnetic Standards, 1915-21 471 



NO. 21. VARIOUS ADDITIONAL OBSERVATORIES. 

 I. Meanook Observatory, 1917. 



During August 30 to September 3, 1917, comparisons" were made under the direc- 

 tion of Sir Frederick Stupart by H. E. Cook, resident observer, at the Meanook Mag- 

 netical Observatory of the Meteorological Service of Canada. The station instrument 

 for declination and horizontal intensity is Elliott magnetometer No. 48 and for inclina- 

 tion is Dover dip circle No. 200. The correction on I. M.S. in declination was obtained 

 by comparison based on magnetograph data, the base-line value being determined by a 

 series of observations with Meteorological Service C.I.W. magnetometer No. 15 (see p. 

 402 for correction of No. 15 on I. M.S.). From the comparisons the following mean re- 

 sult (probable error of 0'.0G) was adopted: 



(a) I.M.S.- Meanook (Elliott magnetometer No. 48)= -0'.5 (I9I6-I9I7). 

 (The corrections on I. M. S. for Elliott magnetometer No. 48 determined in September 

 and October 1906 at Agincourt (see Vol. II, p. 214) were O'.O in declination and 

 0.00056.7/ in horizontal intensity, with some uncertainty, however, because of possible 

 small station-differences.) 



Mr. Jackson also reports in the same reference" that the correction on I. M.S. used 

 for the Meanook results as determined at Agincourt in 1914 and adopted was: 



(6) I. M. S.-Meanook (Elliott magnetometer No. 48) = +0.00031// (1917). 

 (This value does not agree with the 1906 results at Agincourt, doubtless because the 

 intensity constants used for No. 48 in 1906 have been superseded.) 



Apparently the observed results with Dover dip circle No. 200 are accepted without 

 correction. In 1912 the following relation was determined at Agincourt (see Vol. II, p. 216) : 



Toepfer inductor No. 89- Dover circle No. 200 (needles 1,2) = +0'. 1 1 . 

 Since from page 400, 



I. M. S.- Toepfer inductor No. 89= -0U5 



we have : 



(c) I. M. S.-Meanook (Dover dip circle No. 200, needles 1, 2) = 0'.0 (1912). 



II. Series of Comparisons During 1913 by Superintendent Richardson of the 



ESKDALEMUIR OBSERVATORY. 6 



During May to August 1913 Mr. L. F. Richardson, superintendent of the Eskdale- 

 muir Observatory of the Meteorological Office, visited the magnetic observatories at 

 Kew, Greenwich, Valencia, Falmouth, Val Joyeux, De Bilt, and Potsdam. Compari- 

 sons of the field outfit were made at Eskdalemuir, June 19-24, 1913, after obtaining 

 comparisons at the first three observatories named, and again in August 1913 at the 

 end of the field work. The traveling instruments used by Mr. Richardson were Dover 

 unifilar magnetometer No. 40 and Dover dip circle No. 120. They were standardized 

 at Eskdalemuir by comparison with the magnetograms using base-values determined 

 by the then standard instruments of the Observatory, viz, Elliott magnetometer No. 

 60 and dip circle No. 74. The resulting observed differences on the field instruments 

 were then referred to Eskdalemuir by the mean relations determined there, viz: 



(1) Eskdalemuir (Elliott magnetometer No. 60) Dover magnetometer No. 40= 0'.8. f 



(2) Eskdalemuir (Elliott magnetometer No. 60) Dover magnetometer No. 40= 13.47 



or -0.00080//." 



(3) Eskdalemuir (Dover dip circle No. 74) Dover dip circle No. 120= +2'. 3. 



See "Results of Observations in the Canadian Mngnetical Observatories Agincourt and Meanook for the Year 1917," 

 by W. E. W. Jackson, Ottawa, 1920, pp. 33-34. 



1 See "Report by the Superintendent of the Observatory, Eskdalemuir, upon a visit in 1913 to various observatories 

 for the purpose of comparing magnetic standards," by L. F. Richardson. British Meteorological and Magnetic Year Book, 

 1913, part IV, section 2, Edinburgh, 1915, pp. 83-89. 



East declination being reckoned as positive. 



d Differences in H are expressed in gammas only throughout Mr. Richardson's report; // for Eskdalemuir at time of 

 comparisons was 0.1682 C. G. S. unit. 



