DEPARTMENT OF TERRESTRIAL MAGNETISM. 333 



The following persons have taken chief part in the work described: 

 L. A. Bauer, W. J. Peters, J. A. Fleming, H. W. Fisk, S. J. Mauchly, 

 C. R. Duvall, C. C. Ennis. Assistance was also received throughout 

 the year from Mr. H. D. Harradon and Miss Emma L. Tibbetts, and 

 likewise during the summer of 1921 from Dr. James E. Ives, while 

 temporarily associated with the Department, and from Mr. G. H. 

 Keulegan, assistant physicist, November to December, 1920. 



SECTION OF TERRESTRIAL ELECTRICITY.i 



The principal activities during the year under review have been as 

 follows : 



1. Reduction of atmospheric-electric observations. — The reduction of 

 ocean atmospheric-electric observations, referred to in the report of 

 last year, has been continued, with preliminary reports from time to 

 time on various phases of the diurnal variation of atmospheric-electric 

 elements as derived from observations made aboard the Carnegie. (See 

 abstract, pp. 354-356.) The full publication of data and discussion 

 of results will be deferred until after the completion of the Carnegie's 

 present cruise. Considerable headway has also been made in the 

 reduction of the continuous records of potential gradient and conduc- 

 tivity obtained in the atmospheric-electric observatory at Washington. 



2. Ocean atmospheric-electric observations. — The current reports from 

 the Carnegie regarding ocean atmospheric-electric work have been 

 studied in detail and various modifications and additions to the original 

 instructions for the present cruise have been prepared. 



3. Observatory work at Washington. — The observatory maintained 

 on the deck of the Laboratory at Washington, primarily for experi- 

 mental purposes in connection with the development of equipment for 

 the geophysical observatories of the Department, has been continued 

 throughout the year, except for short periods when prevented by special 

 tests in the course of development work and by the training of ob- 

 servers. In addition to the regular work of operating the observatory, 

 standardizing observations were carried out which have made it 

 possible to proceed with an approximate reduction (mentioned above) 

 of the records thus far obtained. 



4. Observatory work at Apia, Samoa. — While Dr. H. M. W. Edmonds 

 was stationed at Apia in charge of the secular-variation work in ter- 

 restrial magnetism pertaining to the islands of the Pacific Ocean, he 

 also made observations of the potential-gradient and allied meteoro- 

 logical observations at the Apia Observatory in accordance with 

 cooperative arrangements between the Department and the New 

 Zealand government (see p. 312). 



5. Design of equipment for atmospheric-electric observatories. — In 

 conjunction with the chief of the magnetic-survey division, designs 



^Report of the chief of the section, S. J. Mauchly. 



