DEPARTMENT OF TERRESTRIAL MAGNETISM. 273 



at the Department's various observatories. Special attention was paid at 

 first to the apparatus required at the Watheroo Observatory in Western 

 Australia, and later for the Huancayo Observatory in Peru. The association 

 with the Department, during the period October 1921 to March 1922, of Dr. 

 H. U. Sverdrup, in charge of the scientific work of the Amundsen Arctic 

 Expedition, provided a unique opportunity to arrange for greatly desired 

 atmospheric-electric data in the polar regions. Accordingly, a special equip- 

 ment was devised for use under the conditions likely to be encountered by the 

 expedition. Arrangements were also completed for special observations at 

 the Watheroo Observatory in connection with the total solar eclipse of Septem- 

 ber 21, 1922. The experimental observatory on the deck of the Laboratory 

 at Washington was continued in operation, not alone for obtaining continuous 

 records of changes in the electric condition of the atmosphere, but also to 

 assist in determining upon the best instrumental appliances. Regarding a 

 rotary slide-wire devised by Dr. Mauchly for producing uniform variation in 

 potential differences, see abstract, page 302. 



(2) Reduction of atmospheric-electric observations made aboard the Carnegie 

 and at Washington. — The results of these observations are proving of unusual 

 interest and will form an important contribution to the subject of atmospheric 

 electricity. 



(3) Methods and equipment for earth-current observations. — Mr. Gish, as 

 already stated on page 271, was assigned to the section to undertake experi- 

 mental work bearing on best methods and instruments for earth-current 

 observations, with special reference to the installations now being made at the 

 Watheroo Observatory. In the furtherance of these studies, leading scientific 

 men were consulted and valuable suggestions were thus obtained. As a 

 result of these conferences and the investigations made at Washington and 

 at Cheltenham, Maryland, decision was reached that the best type of earth- 

 current line would seem to be one having "subterranean lines consisting of 

 leaded rubber-covered cable laid about 18 inches deep in insulating conduit." 

 The precise type of installation decided upon for the Watheroo Observatory 

 is described on pages 300-301. 



(4) Polar-light investigations. — Preliminary studies bearing on this subject 

 have been continued, and a progress report was presented at the annual 

 meeting of the American Geophysical Union, March 1922. (See abstract, 

 p. 305.) 



OBSERVATIONAL AND ADMINISTRATIVE WORK. 



Mr. J. A. Fleming, who has been connected with the Department since 

 its establishment in 1904, was appointed on January 1, 1922, to the new posi- 

 tion of "Assistant Director for Observational and Administrative Work." 



Besides the important land expeditions in Africa, Asia, Australasia, Europe, 

 North America, South America, and on islands of the Atlantic and Pacific 

 oceans, briefly described below, special mention may be made of the safe 

 return in September of the MacMillan Baffin Land Expedition, with which 

 the Department has cooperated, the assigned program of scientific work 

 having been successfully carried out. 



The Department's magnetic observatory at Watheroo, Western Australia, 

 by the end of the year will be the most completely equipped observatory in 

 the Southern Hemisphere for investigations relating to terrestrial magnetism, 



