DEPARTMENT OF TERRESTRIAL MAGNETISM. 307 



a plane. No deviation was found for one of the conditions of maximum 

 dynamic deviation, namely, for the condition that the period of compass 

 swing and the period of the simple harmonic motion are equal. Mechanical 

 difficulties, however, which will probably be overcome, in the operation of the 

 table preclude any final conclusions at the present time. 



An experimental compass was designed to study dynamic and tilting 

 deviations by eliminating one or the other as desired in the laboratory experi- 

 ments. 



Results of Magnetic Observations on the Maud Expedition, 1918-1921. H. U. Sverdrup 

 and C. R. Duvall, with introduction by Roald Amundsen. Terr. Mag., vol. 

 27, Nos. 1 and 2, 35-56 (March-June 1922). 



In a brief introduction, Captain Amundsen emphasizes the value to the 

 Maud Expedition of the cooperation of the Department of Terrestrial Mag- 

 netism. He lays special stress on the loan of the most suitable instrumental 

 equipment, on the early publication of the results, and on the advantage of 

 Dr. Sverdrup's association with the Department, not only to this publication 

 but also to the future work of the expedition. 



In April 1918, Captain Roald Amundsen and Dr. Fridtjof Nansen met with 

 Dr. L. A. Bauer in Washington to discuss plans for magnetic work on Captain 

 Amundsen's forthcoming Maud Expedition. Guided by the Arctic experience 

 of Captain Amundsen, Dr. Nansen, and Mr. Peters, a member of the Depart- 

 ment, it was decided that magnetometer No. 8 and Dover dip-circle No. 205, 

 with certain minor modifications, would be best suited for magnetic observa- 

 tions in the Arctic. 



After modification in the shops of the Department, under Mr. Fleming's 

 direction, these two instruments, together with numerous accessories and 

 complete instructions for observing according to the Department's methods, 

 were supplied to the Maud Expedition. For making magnetic measurements, 

 the expedition also had, besides these instruments, Dover land dip-circle No. 

 154 and a Toepfer and Son photographic registering declinometer. 



The Maud, Captain Amundsen's ship, constructed especially for naviga- 

 tion in the icy seas of the Arctic, sailed from Vardo, Norway, July 18, 1918. 

 Captain Amundsen's intention was to follow the Arctic coast of European 

 and Asiatic Russia as far east as 165° E., then to proceed northward until the 

 Maud was frozen into the polar drift. While drifting across the Polar Sea, 

 it was planned to make oceanographic, meteorological, and magnetic observa- 

 tions. 



During the three summers of 1918, 1919, and 1920, the Maud made every 

 effort to reach the desired longitude on the coast, and then to force her way 

 into the large drifting ice-fields to the north. The early freeze of each suc- 

 ceeding fall found her still struggling with the coastal ice, and so the three 

 winters were spent frozen fast in the fixed ice on the Siberian coast. 



The first winter, 1918-19, the Maud was frozen in within 200 meters of the 

 shore-line on the east coast of the Chelyuskin Peninsula, in longitude 105° 40' E. 

 The second winter she was at Ayon Island, in longitude 167° 43' E., and the 

 third winter, at Cape Serdze Kamen, in longitude 171° 39' W. 



Except for two stations occupied at Jugor Strait and one at Port Dickson 

 in the summer of 1918, all the magnetic observations of this expedition were 

 made while the Maud was frozen fast during the three successive winters. 

 Besides the observations at the winter-quarters stations, other magnetic 

 stations were established on numerous sledge trips, extending up to several 

 hundred miles in some cases. The majority of stations occupied on these 

 trips are on or near the coast, the farthest station being about 75 miles inland. 



