336 CARNEGIE INSTITUTION OF WASHINGTON. 



the average parallel was about 52° S. Declinations had been observed 

 aboard the Carnegie generally twice a day throughout the passage of 

 118 days, and horizontal intensities and inclinations were observed 

 once a day. The preliminary computations gave a total resultant 

 negative current passing from the air perpendicularly through the 

 surface of the zone, from the South Pole to the circuit, of 80 times 10* 

 amperes, which corresponds to an average current-density of 0.016 

 ampere per square kilometer. 



Average diurnal changes. — Preliminary values of the average annual 

 changes in the magnetic elements over the Indian Ocean were deduced 

 from the Carnegie results obtained in 1911, 1916, and 1920. The work 

 was begun by the commander of the Carnegie, J. P. Ault, while at sea 

 on Cruise VI, and has been amplified subsequently in the office. Two 

 methods were used, based upon the assumption that differential cor- 

 rections to the results for small differences in the geographic coordi- 

 nates may be computed with sufficient accuracy from data derived 

 from the most recent magnetic charts. These two methods are some- 

 what shorter than those described in Volume III (pp. 431-432) of the 

 "Researches of the Department of Terrestrial Magnetism," but the 

 latter methods have the advantage of being entirely independent of 

 the approximative data required and obtainable at present only from 

 the charts. 



Standardizing instruments. — The resumption of field activity, not 

 only by the Department, but also by other organizations interested in 

 magnetic work, both American and foreign, placed unusual demands 

 upon the Department's facilities for the standardizing of field instru- 

 ments. The chief of the division accordingly assisted the Magnetic 

 Survey Division in this work by making comparison observations 

 simultaneously with Mr. H. W. Fisk between May 25 and July 8, 1921. 



Field reports. — Considerable time was given to editing the reports 

 by field parties. These reports by different observers, written in re- 

 mote parts of the world under most varied and trying conditions, con- 

 tain a large amount of valuable and interesting material, all of which, 

 however, is too voluminous to publish. With the help and advice of 

 the Magnetic Survey Division, the material was carefully condensed 

 and prepared for publication in Volume IV of the ''Researches of the 

 Department of Terrestrial Magnetism." 



The table of magnetic results for Volume IV was completed by Miss 

 Tibbetts under the supervision of the Magnetic Survey Division. 

 Blue prints and manuscript forms for various investigations and reports 

 have been made from time to time by Mr. Dixon. Memoranda for the 

 determination of the height of the aurora were prepared for the use of 

 the MacMillan Baffin Land Expedition. The first audit of the 

 monthly disbursements made by the various divisions, expeditions, and 

 observatories, involving in many cases problems of fluctuating foreign 



