216 



Reports on Special Researches 



howc\Tr; for this clement the standardizing instruments could not be mounted on the 

 observatory pier for declination, it being impracticable, as already explained, to dismount 

 the Observatory declinometer; accordingly, the discordance in the results may arise, in 

 part, from causes other than purely instrumental ones. 



In February 1911 a new determination of the instrumental constants of Elliott No. 

 98 was made by the Agincourt Observatory, as the result of which, according to Director 

 Stupart's letter of March 17, 1911, it was found that the H values computed with the old 

 constants required a correction of 0.001 16i/. The old constants had been determined 

 at Kew. Hence we have finally, up to 1911: 



VI. C. /. W.- Agincourt (Elliott No. 9S corrected) = +0.00023H. 



Of dip comparisons later than those of 1906, there is but one series available, namely, 

 comparisons made by the Agincourt Observatory in 1910 between the Agincourt dip circle 

 (Dover No. 200, needles 1 and 2) and C. I. W. dip circle (Dover No. 205, needles 1 and 2), 

 standardized at Washington in April 1910 and again in March 1913, the mean correction 

 being 0'.4; this correction has been applied to the observed values with No. 205. No. 

 200 was mounted on Observatory pier D, and No. 205, on pier E; the observations were 

 simultaneous, but stations were not exchanged. 



Table 1 D. Rcifults of I ncli7tation Comparisons ul the Agincourt Observatory, 1010. 



Comparisons bet\\pen Dover No. 200 and Dover No. 130 were made by the Agincourt 

 Observatory, Nov. 1911 and Feb. 1912, No. 200 being on pier D, and No. 130 on pier . 

 The mean result of 5 sets of simultaneous observations, without exchange of stations, was : 



VIII. Dover No. 200 -Dover No. 130= -0'.9. 



Furthermore, in 1912, Dover No. 200 was compared with the new inclination standard 

 of the Agincourt Observatory, namely, Toepfer earth inductor No. 89 mounted on pier C, 

 No. 200 being on pier D; Mr. Menzies observed alternately with the two instruments, 

 but stations were not exchanged. From 22 sets it was found that the correction of 

 Dover No. 200 on this earth inductor was +0'.ll, hence: 



IX. Agincourt earth inductor No. 89-Dover No. 200= +0'.l. 



From VH and IX we get for 1910 to 1912, assuming no changes in the dip circles used 

 in the comparisons, and that the station-differences are negligible quantities: 



X. C. I. W.- Agincourt earth inductor No. 89= 4-0'.3. 



Assembling the chief results and referring them to I. M. S. (see p. 273), we obtain: 



(1) I. M. S.- Agincourt (Toronto declinometer) = - I'.l? (1906-10). 

 (la) I. M. S.- Agincourt (Elliott magnetometer No. 98) = + 0.00008W ( 1 9 1 1). 

 (14) I. M. S.- Agincourt (Toepfer inductor No. 89)= +0'.8 (1910-12). 



