DEPARTMENT OF TERRESTRIAL MAGNETISM. 283 



The study of the effect of dynamic deviations upon results from 

 magnetic instruments mounted on supports subject to motions such 

 as are encountered, for example, on board ship, has been facilitated 

 with the aid of automatic records of the roll and pitching being made on 

 the Carnegie (see p. 300), 



The following persons have taken chief part in the investigational 

 work in terrestrial magnetism: L. A. Bauer, W. J. Peters, J. A. 

 Fleming, H. W. Fisk, C. R. Duvall, C. C. Ennis, and H. B. Hedrick. 

 For further accounts of above work, see abstracts, pages 298 and 299. 



MAGNETISM IN GENERAL. 



The completion of the non-magnetic building, known as the Experi- 

 ment Building, at the Department's site in Washington, enabled 

 Dr. S. J. Barnett to repeat, under the desired favorable conditions, 

 his important exiDeriments on magnetization by rotation in accord- 

 ance with the two previously used methods, that of electro-magnetic 

 induction and that of the magnetometer, with improvements and 

 some modifications (see particulars on pages 305-306). For views of 

 the Experiment Building see plate opposite page 306. 



Preparations have also been made for further experiments upon the 

 converse effect — rotation by magnetization. 



For progress concerning construction of sine galvanometer, see 

 page 307. 



Assistance was rendered Dr. Barnett in the work of the Division of 

 Experimental Work by J. A. Fleming (in connection with construc- 

 tion of the Experimental Building and of apparatus), S. J. Mauchly 

 (assistant chief), C. A. Kotterman (laboratory assistant), and Instru- 

 ment-makers C. Huff and G. H. Jung. 



TERRESTRIAL ELECTRICITY. 



The Section of Terrestrial Electricity, under the immediate charge 

 of Dr. S. J. Mauchly, has been continued as part of the work of the 

 Division of Experimental Work. Details of the work of the section 

 will be found on pages 307-309. 



At the laboratory at Washington are being made the only continu- 

 ous photographic registrations in the United States of the electric 

 potential-gradient and the electric conductivity of the atmosphere. 

 These photographic records, aside from their pm'ely scientific value, 

 have proved of practical interest in connection with studies of electric 

 disturbances in the atmosphere affecting wireless transmission, and use 

 of them has been, and is being, made in this connection by the Signal 

 Corps and the Bureau of Standards (see p. 309). 



The improvements in instrumental equipments and methods of 

 observation have made it possible to secure definite results of the 

 effects upon the electric condition of the atmosphere which accompany 

 an echpse of the Sun. The electric results obtained by the Depart- 



