Comparisons >f Magnetic Standards, 1915-21 



(4d) I . M . S. - Dominion C servatory (Cooke magnetometer No. 1 5) = + 0.00 1 06// (191 

 (4e) I. M.S.- Dominion C servatory (Earth inductor No. 1911, by Toepfer)= -0'.25 



(1915). 

 (4/) I. M. S. Dominion C servatory (Dover dip circle No. 145, needles I and 2) = +0' 



(1915). 

 (4g) I. M. S. Dominion C ;ervatory (C.I. W. universal magnetometer No. 20)"= -0' 



(1915-1921). 

 (4/i) I. M. S. Dominion C servatory (C.I.W. universal magnetometer No. 20)* = 



0.00023//-(-I9l5.>) 0.00010// (Mar. 1915-June 1921, constants of March 25, 



1916). 

 (4) I. M. S. Dominion < servatory (C.I.W. universal magnetometer No. 20)* = 



0.00010// (July 1921 :onstants of July 31, 1921). 

 (4y) I. M.S. Dominion C ervatory (C.I.W. universal magnetometer No. 20)*= -0 1 . 1 



(1915-1921). 



Previous Comparison of the Dominion-Observatory Instruments. 



Simultaneous comparisons declination and in horizontal intensity were made on 

 April 7 and 9, 1908, between agnetometers D.O. No. 1977 and C.I.W. No. 3, 

 stations A m and C m , Washingto D. C. (see page 172 of Volume I, Researches, D 

 merit of Terrestrial Magnetism , for descriptions of stations); the station-ditT- 

 having been determined from her observations at the time, the stations wen 

 exchanged. From 11 sets of ddination comparisons, the mean value of 1 1.. M.S. 

 (magnet 10)] was found equal to -5'.2. From 5 sets of horizontal-intensity compar 

 it was found that the mean valu of [I. M.S. 1977 (magnets 46 and 10)] = -0.00258// 

 This value agrees well with tha determined at Washington in 1915; too great v. 

 however, can not be given the )08 result, since the reductions for magnetometer No. 

 1977 had to be based on the n an value of distribution coefficient derived from only 

 the 5 sets of comparison-observ: ions. 



Dr. O. Klotz, director of he Dominion Observatory, courteously supplied the 

 results of declination-compariso s at Ottawa, 1912-1915, between D.O. magnetometer 

 Tesdorpf No. 1977 and Cooke K 15, as also the results of inclination-compariM 

 Ottawa, 1912-1915, between D. . earth inductor Toepfer No. 1911 and DO c 

 Dover No. 145 (needles 1 and i The observations for these comparisons were! 

 alternately on the north and so h piers in the absolute magnetic observatory wi 

 exchange of stations, except in )14, when an exchange was made for the deed' ' '' 

 comparisons, and the station-d erence was found to be O'.O. Table 4J 

 the results of these comparisons 



Dr. Klotz likewise suppUe the results of comparison-observations marl ' 

 Absolute Observatory at Aginc irt from 1908-1915, between the instrument! 

 Dominion Observatory and tl se of the Agincourt Observatory All 

 with D.O. magnetometer, Tesdc f No. 1977 (magnet 10 for declination' exceT' 

 and magnets 46 and 10 for horiz tal intensity), were made on pier B and th 

 values were derived from eye-r< lings of the vanon- " t 



dip circle, Dover No. 145 (need s 1 and 2), wer^ 

 with the Agincourt dip circle, l>ver No. 200 

 As stations were not exchanged it was nee- 

 Tables 4K, 4L, and 4M, that tl station ^ 

 magnetometer No. 1977 were th ;e adr 

 using the mean value of P' (Q a um 



of P' derived from a set of obsei ife 



constants for 1914 were used. 



