1898-1902. No. 6.] TERRESTRIAL MAGNETISM. 



Strenuous efforts were made, however, to overcome ttie difficulties. 

 I may mention, for instance, ttiat in the summer of the last year, 1902, 

 a new brass rod intended for the deflection-observations was made on 

 board, the one belonging to the apparatus having proved to be too short, 

 as even the weakest deflector introduced at the greatest distance turned 

 the needle 90°. With the new deflection-rod it was possible to place 

 each deflector at two distances, with a reasonable angle of deflection in 

 all four combinations. 



The previously-mentioned magnetic apparatus E. A. Zschau, No. 289, 

 also used on this Expedition, was described by me in my working-up 

 of the observations from the first Fram Expedition^. It is a combina- 

 tion of the well-known Neumayer declinatorium and a Fox circle, to 

 which is added a vibration-box with suspension tube. On each side of 

 the alhidade belonging to the horizontal circle of the declinatorium, a 

 brass rod can be affixed for the application of the vibrating magnet as 

 deflector. The horizontal circle is furnished with two verniers, which 

 give a direct reading of 0.5'. Increasing figures in the reading answer 

 to increasing east declination. 



The constants of the apparatus were determined in Hamburg in 

 June, 1893, by Geheimerat Neumayer and Captain Scott-Hansen in con- 

 junction, and six months after the return of the first Fram expedition, 

 in March, 1897, at Wilhelmshaven by E. Stijck, assistant at the 

 Marine Observatory there, the result of his observations showing that 

 on the whole the constants had remained unchanged throughout the first 

 Fram Expedition. The observations made by Captain Baumann and 

 Captain Isachsen at Wilhelmshaven in April, 1898, which were sub- 

 sequently calculated by Stock, were in such harmony with the results 

 previously found, that it may be assumed that the constants of the in- 

 struments at the time of the departure of the 2nd Fram Expedition, were 

 the same as at the time of the return of the first. 



At the end of November, 1902, three months after the Sverdrup 

 Expedition had come back to Christiania, Captain Roald Amundsen who 

 was then engaged in fitting out his expedition with the "Gjoa" to the 

 regions about the magnetic north pole, obtained the loan of the Frajn's 

 magnetic instruments, and took them to Potsdam, where, with the kind 

 assistance of Professor Ad. Schmidt, the director of the magnetic obser- 



' The Norwegian North Polar Expedition, 1893-1896. Scientific results. Edited 

 by Fridtjof Nansen, Vol. II, Mem. VII. Terrestrial Magnetism. By Aksel S. 

 Steen, pp. 2—6. In the following pages, this paper will be referred to as 

 "Nansen Exped. T. M." 



