446 



Special Reports 



5, designated Z>5, is used for declination and intensity, and pier 4, designated D-l, is 

 used for inclination. For the work in November, absolute observations were made 

 with the C.I. W. instruments at the stations Z>4, and D5, the Observatory values being 

 deduced from the magnetograph data. The Observatory azimuth mark, the central of 

 three vertical lines on a stone pier near the tennis court, was used; its azimuth from 

 station B is 100 14'.4 west of true south, and from station D5, 94 36'. 1 west of true 

 south, these values being supplied by Prof. F. H. Bigelow who is in immediate charge 

 of the work at Pilar. The Pilar results were obtained by Observers O. Liitzow-Holm 

 and Bliithgen of the Observatory staff. The C.I.W. observations during March and 

 April were made by Observers H. M. W. Edmonds and A. D. Power, and during Novem- 

 ber by Observer A. D. Power. 



The Observatory instruments used in the comparisons of March and April were 

 Dover-Kew magnetometer No. 175 and Toepfer earth inductor No. 3; these are the 

 standard instruments of the Observatory, and are used regularly for the control of the 

 magnetograph data upon which the series of comparisons during November depend. 

 The C.I.W. instruments used were magnetometer No. 5 for declination in April, and 

 magnetometer-inductor No. 25 for declination in November and for horizontal intensity 

 and inclination during both series. The I. M. S. values given depend upon the constants 

 and corrections finally adopted for the C.I.W. instruments. 



Table 13A. Results of Declination Comparisons at the Pilar Observatory, 191"/ 



Series 



Date 



Local mean time 



From 



To 



Declination obtained 1 



I. M. S. 



Pilar 



I. M. S.- 

 Pilar 



Remarks 



1917 

 April 3 

 3 

 3 

 3 

 3 

 3 

 4 

 4 

 4 

 4 

 4 

 4 



h m 

 14 21 



14 35 



15 18 



15 32 



16 12 

 16 26 



8 58 



9 12 

 9 52 



10 06 



11 20 

 11 34 



h m 

 14 30 



14 44 



15 27 



15 41 



16 21 

 16 35 



9 08 



9 22 



10 02 



10 16 



11 30 

 11 44 



Mean value of (I. M. S. Pilar) 



II 



+8 



16.5 

 16.5 

 16.9 

 16.4 

 14.9 

 15.1 

 10.7 

 10.8 

 12.0 

 12.2 

 14.9 

 15.5 



+8 



Mean value of (I. M. S. Pilar) 



Mean value of (I. M. S. Pilar) from I and II 



+ 8 17.5 

 17.3 

 16.3 

 16.0 

 17.0 

 17.0 

 11.2 

 11.4 

 12.5 

 12.9 

 15.7 

 16.7 



+8 13.1 

 13.8 

 14.1 

 14.2 

 11.6 

 08.7 

 07.1 

 11.2 

 12.7 

 16.4 

 14.7 

 II. 1 



-1.0 

 -0.8 

 +0.6 

 + 0.4 

 -2.1 

 -1.9 

 -0.5 

 -0.6 

 -0.5 

 -0.7 

 -0.8 

 -1.2 



-0.76 



-1.7 

 -1.7 

 -0.6 

 -1.5 

 -0.5 

 -0.8 

 -1.7 



-1.07 



-0.9 



C. I. W. magnetometer No. 5 at 

 B; Pilar magnetometer No. 175 



:it />.',. 



C. I. W. magnetometer No. 5 at 

 Db\ Pilar magnetometer No. 175 

 at B. 



C. I. W. magnetometer No. 25 at 

 Db throughout; Pilar values are 



from magnetograph data con- 

 trolled by observations with mag- 

 netometer No. 175 at Db. 



' The values on April 3 and 4 are all referred to Db; Db B0'.b. 



