DEPARTMENT OF TERRESTRIAL MAGNETISM. 235 



Land magnetic survey. — The land magnetic work was planned particularly 

 with reference to securing required data concerning the magnetic secular 

 variation and the diurnal variation. 



Atmospheric electricity. — The registrations of the electrical conductivity 

 of the atmosphere are now being made at both the Watheroo and Huancayo 

 observatories, in addition to the magnetic registrations for the three elements, 

 and it is hoped that the continuous registration of potential gradient may be 

 undertaken at each of these observatories by the beginning of the new year. 

 Continuous potential-gradient observations and occasional electrical-conduc- 

 tivity observations are being obtained regularly at the Apia Observatory. 



Earth currents. — The earth-current installations are complete at the 

 Watheroo Observatory, and this work will be on a satisfactory basis by the 

 new year; it is hoped that corresponding installations and observations may 

 be undertaken at Huancayo some time in 1925. 



Computational and publication work. — Good progress was made also in com- 

 putational and publicational matters, particularly with respect to the ocean 

 magnetic survey accomplished through 1921 on the Carnegie. The results 

 obtained indicate most strongly the desirability of resuming at an early 

 date the cruises of the Carnegie for the continued investigation of the magnetic 

 field of the Earth and, especially, of its secular variation, of apparent oceanic 

 magnetic anomalies, and of the electric field of the Earth (atmospheric elec- 

 tricity and earth currents). 



Cooperative work. — The Department continues to cooperate with other 

 organizations and expeditions and with various governments in advancing 

 important matters within its fields of research. 



The satisfactory arrangements made with outside manufacturers for the 

 construction of magnetic instruments for other organizations promise to 

 make it possible to devote an increasing amount of time in the instrument 

 shop to the experimental development of applicances for laboratory and 

 observatory researches. 



The final detailed drawings for piers and installation of variometers for 

 exhibit purposes in the new building of the National Academy of Sciences at 

 Washington were completed. 



The following abstracts from the reports of the Assistant Director and 

 of the section chiefs summarize briefly the work done during the year. 



OCEAN WORK.^ 



Vessel maintenance. — The Carnegie remained out of commission at the 

 wharf of the Washington and Colonial Beach Steamboat Company in Wash- 

 ington throughout the year in charge of a caretaker. The housing of the 

 vessel (see p. 274 of last year's report) was completed early in November and 

 has proved entirely satisfactory. 



The continued general interest in the Carnegie and her work was evidenced 

 by the many visitors who, during the year, asked to inspect her, even though 

 she was out of commission. 



Final reductions of observations at sea. — The final computation and sum- 

 maries of ocean magnetic results from 1915 to 1921 and the manuscript 

 to accompany these final results, to be published as one of the volumes of the 

 "Researches of the Department," were completed in October by the chief 



^ From the report of the chief of the section, J. P. Ault. 



