Comparisons of Magnetic Standards, 1915-21 



407 



while the mean from 12 comparisons through the magnetograph on February 13, 14, 

 19, 25, and 27 was: 



(b) Cheltenham-C. & G. S. No. 40= +0.00018//. 



The comparisons during March at Washington were made by the method of simul- 

 taneous observations and exchange of stations at piers N m and S m of the Standardizing 

 Magnetic Observatory, Mr. H. W. Fisk observing with C.I.W. magnetometer No. 3 

 and Mr. W. W. Merrymon, of the Coast Survey staff, with C. & G. S. magnetometer 

 No. 40. The result of the 12 comparisons in declination was: 



(c) I.M.S.-C. &G. S. No. 40=-0'.l6, 



while from 6 complete sets in horizontal intensity it was found that 

 (</) I.M.S.-C. &G.S. No. 40=4-0.00002//. 



From (a) and (c) and (b) and (d) we get 



(e) I. M.S.- Cheltenham = +0'.05, and 

 (/) I. M.S.- Cheltenham = -0.00016//. 



SUMMARY. 



Table 2E summarizes the chief results as already published in Volume II" and as 

 given above (horizontal-intensity results prior to 1913 are referred to basis of C. & G. S. 

 standard adopted beginning with 1913, b viz, standard previously used diminished by 

 0.001//). 



Table 2E. Summary of Corrections on Standards for Cheltenham Observatory. 



' Referred to standard for horizontal intensity adopted by the Coast and Geodetic 

 Survey beginning with 1913. 



These results given small weight because the axis of rotation of Wild-Edelmann 

 inductor No. 26 could not be precisely oriented in the magnetic meridional plane for 

 each observation (see remarks Series II, 1917). 



Hence we obtain weighted mean values as follows : 



(2) I. M.S. -Cheltenham (Wild-Edelmann declinometer No. 26) = 0'.0 (1908-1918). 

 (2a) I. M.S. -Cheltenham (Wild-Edelmann magnetometer No. 26) =- 0.00006// ( 1 908- 



1918).' 

 (2b) I. M.S. -Cheltenham (Wild-Edelmann inductor No. 26) = +0'.9 (1908-191 7). d 



" See Res. Dep. Terr. Mag., Vol. II, pp. 226-229. 



6 See Faris, R. L., Results of Magnetic Observations Made by U. S. C. & G. S. in 1913, Washington, 1914, pp. 1-52. 



' See foot-note 1 to Table 2E. 



d Director E. Lester Jones of the Coast and Geodetic Survey in a lotter dated January 15, 1917, states that C. & G. S. 

 Schulze earth-inductor No. 1, from the Porto Rico magnetic observatory, had been compared recently at Cheltenham after 

 receiving a thorough overhauling in the instrument-shop. The preliminary results of these observations gave (Cheltenham 

 C. & G. S. No. 1) = 0'.8 as compared with value 1' derived from comparison observations made in 1904; this indicates 

 excellent maintenance of inclination standard at Cheltenham between 1904 and 1917. Using (I. M. S. Cheltenham) = 

 + 0'.8 the correction for Schulze inductor C. & G. S. No. 1 on I. M. S. would be thus O'.O. 



