DEPARTMENT OF TERRESTRIAL MAGNETISM. 337 



■exchange, have been carefully made by M. B. Smith, who also pre- 

 pared all financial statements. 



The personnel of the division during the year included W. J. Peters, 

 chief; C. R. Duvall, expert computer, to January 1, 1921, when he 

 was transferred to the Division of Research in Terrestrial Magnet- 

 ism and Electricity; M. B. Smith, chief clerk and cashier; Miss 

 Emma L. Tibbetts, stenographer and computer; A. J. S. Dixon, mes- 

 senger clerk. 



MAGNETIC SURVEY DIVISION.i 



Mr. J. A. Fleming continued as chief of the Division throughout the 

 year, with the effective cooperation of Mr. H. W. Fisk as chief of the 

 Section of Land Work. Captain J. P. Ault was chief of the Section of 

 Ocean Work and was in command aboard the Carnegie throughout the 

 year (for report see pp. 317-323) . Mr. Fleming was on an inspection trip 

 to the Carnegie during February 20 to March 13 while she was at San 

 Francisco, and again during July 13 to 18 to the Bowdoin of the Mac- 

 Millan Baffin Land Expedition at Wiscasset, Maine. In his absence, 

 Mr. Fisk was acting chief of the Division. 



Reduction of magnetic results. — The comparisons and revisions of 

 observations and compilation of resulting data obtained during 1920 

 at land stations were completed and included in the manuscript for 

 Volume IV of the Department's "Researches." The reductions of the 

 field observations made during 1921 were kept current. Good progress 

 was also made in the reductions of the observations obtained during 

 November 1918 to July 1920 by the ''Maud Expedition," under the 

 leadership of Captain Roald Amundsen (see p. 325) ; Mr. Duvall did 

 most of this work. 



Instrumental constants and standardizations. — An extension of the 

 discussion of constants for standard magnetometer No. 3, to include 

 the years 1920 and 1921 (to September), was made; the series of 

 observations with this instrument now covers a period of 15 years from 

 1907. The results of the discussion indicate that only a small correction 

 will be necessary to values of horizontal intensity based on the con- 

 stants originally adopted. To reduce the labor of computation for 

 distribution cooefficients of magnetometer constants, Mr. Fisk de- 

 veloped a simplified form of the well-known formulae already in use. 

 Further extension was also made of the investigation undertaken by 

 Mr. Fisk on dip-needle errors arising from minute pivot-defects. 

 Extensive comparisons with the Department's standard magnet- 

 ometer No. 3 and earth-inductor No. 48 were made for instruments 

 used or to be used in the field to determine their corrections. All 

 comparisons were made by the method of simultaneous observation 

 with exchange of station. Some trouble was experienced because of 

 increasing disturbance caused by leakage from electric-car circuits 



^From the report of J. A. Fleming, in charge. 



