DEPARTMENT OF TERRESTRIAL MAGNETISM. 341 



course of publication. A paper on the instrument was presented to 

 the American Geophysical Union on April 18, 1921 (see abstract, pp. 

 346-347). 



Magnetization and rotation. — No further work on rotation by mag- 

 netization has yet been practicable and in the work on magnetization 

 by rotation only a slight amount of progress has been made in further 

 preparation for the experiments on large rods by the method of electro- 

 magnetic induction. A great deal of work, however, has been done 

 by the magnetometer method; and much progress has been made in 

 the elimination of systematic errors. The possible error due to non- 

 uniformity of speeds has been removed or reduced by the substitution 

 of gear drive for belt drive. The effects of torsion have been studied 

 more thoroughly and have been more completely eliminated. Eddy- 

 current effects have been further studied by superposing on the residual 

 field in which the rotor moves cross-fields and longitudinal fields; and 

 they have been further eliminated by reversing the magnetometer 

 system and by transferring the rotating apparatus to a new compensat- 

 ing frame which produces a much more nearly uniform magnetic field 

 than that of the frame used before. Experiments have been made with 

 four positions of the magnetometer. Other improvements are in 

 progress. An account of this work up to December 1920 was presented 

 by S. J. and L. J. H. Barnett at the Chicago meeting of the American 

 Physical Society. (See Physical Review, 17, 1921, p. 404.) 



In connection with the magnetic tests on the materials of the sine 

 galvanometer, a little attention has been devoted to the general 

 problem of measuring small susceptibilities with astatic magnetometers. 



At the joint meeting of the American Physical Society, and the 

 American Association for the Advancement of Science, Section B, in 

 December, Dr. Barnett presented, by invitation, an extended paper on 

 "The Electron Theory of Magnetism," an abstract of which will be 

 found on pages 345-346. The complete paper is published in >Sa- 

 ence, n. s. vol. 53, 1921, p. 465. 



In Nature, March 3, 1921, he published a brief paper on "Molecular 

 and Cosmical Magnetism," an abstract of which is given on page 345. 



He has continued to serve on the National Research Council com- 

 mittees on "Electrodynamics of Moving Bodies" and "Theories of 

 Magnetism." 



Mr. Kotterman has continued his valuable services in instrumental 

 work, laboratory assistance, photographic work, and clerical work. 



From this division, Mr. Huff, after finishing two excellent gear 

 boxes for use in the fundamental work in magnetism, was transferred 

 to work on the sine galvanometer, and later to work under Dr. 

 Mauchly's supervision; Dr. Wait and Dr. Ives have rendered important 

 services in connection with the linear measurements upon the coils of 

 the sine galvanometer; and Mr. Jung has done the chief instrumental 

 work on this instrument. 



