214 



Reports on Special Researches 



and Dover dip circle No. 130, with needles 1 and 2, for dip. In November 1906, Elliott 

 magnetometer No. 98 was substituted for Elliott No. 48; dip circle Dover No. 130 was also 

 later superseded by Dover No. 200 with needles 1 and 2. Accordingl}', only the mean 

 results of the 1906 comparisons are given.^ The instruments used by Observer P. H. Dike 

 for the C. I. W. observations were: Coast and Geodetic Survey magnetometer No. 20 and 

 Dover dip circle No. 172 with needles 1 and 2. Series A and B were obtained, respectively, 

 before and after Mr. Dike's field work in Canada. 



Station T was placed 5.5 feet south of the Observatory building, and in line with the 

 declinometer pier and the azimuth mark about 4 miles distant. The same mark and the 

 same azimuth could therefore be used at both T and the decUnometer pier but, for the reason 

 mentioned above, the stations could not be exchanged; accordingly, any possible difference 

 in declination between the two stations is included in the quantity C. I. W. Agincourt 

 (Toronto decUnometer) , given in Table 1 A. 



The observatory' data for D and H were derived from the magnetograms; however, 

 two of the Z)-values were obtained from eye-readings with the declinometer, made simul- 

 taneously with the D-observations by Mr. Dike. The //-observations by Mr. Dike were 

 made partly at station I and partly at station T. The results of the inclination compari- 

 sons were obtained from simultaneous observations with the two dip circles compared, the 

 stations used being /, T, and D. 



The corrections applied to Mr. Dike's values to refer them to the adopted C. I. W. 

 standards were: +0'.5 (for declination), -^0.00110i/ (for horizontal intensity), and 0'.8 

 (for inclination). These corrections resulted from comparisons at Washington and at the 

 Cheltenham Observatory before and after the Agincourt comparisons. No appreciable 

 difference was found in inclination between stations /, T, and D; for horizontal intensity 

 the small station-difference of I T= +1-07 resulted from the ob.servations, and was 

 applied to the observed values. 



Table 1 A. Results of Comparisons at the Agincourt Observatory in 1906. 



From November 1900 to April 1908, horizontal-intensity comparisons were made 

 at the Agincourt Observatory between the two Elliott magnetometers, Nos. 48 and 98. 

 The following difference, as communicated by Director R. F. Stupart on January 10, 1911, 

 was found : 



II. Agincourt (Elhott 98 uncorrected) -Agincourt (Elliott 48) = +107= +0.00061//. 

 Accordingly, from I and II, we have: 



III. C. I. W.- Agincourt (Elliott 98 uncorrected) = -16.67= -0.00102//. 



In 1909 comparisons were made at Agincourt by the Meteorological Service of Canada 

 between magnetometers Elliott No. 98 and C. I. W. No. 8, loaned the Service for use during 

 the expedition in 1908-1909 of the steamer ^rdic; No. 98 was mounted on Observatory pier C, 

 and No. 8 on pier B. This series, IV, was obtained soon after the return of the expedition. 

 C. I.W. No. 8 was standardized at Washington before and after this expedition and the follow- 

 ing corrections on the C. I.W. standards were found : for declination, +0'.8, and for horizontal 



'The observations are published in full in Terr. Mag., vol. 16, 1911, pp. 79-81. 



