338 CARNEGIE INSTITUTION OF WASHINGTON. 



about five-eighths mile to the west. Strict simultaneity of com- 

 parison observations eliminated any harmful effects from this source. 

 Observations were made to determine the moments of inertia for the 

 long-magnet systems of magnetometers Nos. 3, 16, 20 (2 series), 24, 

 26, 27, and 28. While no change was found in the case of No. 3, the 

 gradual change with time for magnets of the type used for the other 

 instruments reported in last year's report^ was confirmed. The 

 results of the comparisons of instruments were very satisfactory; Mr. 

 Fisk made all the observations with the standard instruments, while 

 Mr. Peters did a large part of the work required for the other instru- 

 ments; Messrs. Duvall and Ennis have assisted in the reductions. 



Correlation of magnetic standards. — This investigation was continued, 

 utilizing the additional observatory comparisons obtained by field 

 parties during the interval 1914 to 1921. The general conclusions 

 resulting from the discussion of earlier comparisons (see pp. 211 to 278, 

 Vol. II of the Department's ''Researches") are further confirmed. 



Absolute standard in horizontal intensity. — Upon the completion of 

 sine galvanometer No. 1, constructed according to the design by Dr. 

 Barnett, an investigation as to an absolute standard in horizontal 

 intensity was begun by Messrs. Fleming, Fisk, and Ives. Extended 

 comparisons were made between the sine galvanometer and Depart- 

 ment standard magnetometer No. 3, and a preliminary report was 

 prepared on the results. The agreement between the instruments is 

 satisfactory and indicates that an absolute accuracy of 0.0002/f , where 

 H is the horizontal intensity, can be readily secured with well-designed 

 magnetometers. The sine galvanometer functioned well, the limita- 

 tions as to precision of results depending upon the accuracy with which 

 the electrical current could be measured with the accessory apparatus; 

 there appears little reason to doubt that, even with the somewhat 

 experimental apparatus for current measurements used in this pre- 

 liminary work, a precision of 0.0001//" is readilj^ obtainable. It is 

 planned to extend the work later by using different methods for measure- 

 ment of current and to make improvements in switch-and-circuit 

 arrangements, as well as to provide small, portable-type storage- 

 batteries for current. 



Instructions and development of field work. — The resumption of greater 

 activity in field work since April and necessary preparation of instruc- 

 tions and training of new observers consumed much time. 



Miscellaneous work. — Assistance in making drawings for various 

 purposes was given by Mr. Ennis. The greater part of the miscellane- 

 ous, clerical, and stenographic work in the Division was efficiently 

 done by Mr. J. J. Capello, property and shipping clerk. 



'C/. Annual Report of the Director of the Department of Terrestrial Magnetism for the year 

 1920, Year Book of the Carnegie Institution of Washington, p. 302. 



