6 AKSEL S. STEEN. TERRESTRIAL MAGNETISM. [NORW. POL. EXP. 



a Fox apparatus 1 for the determination of inclination and intensity, accom- 

 panied by a vibration-box with suspension-tube for observations of vibration. 

 On the alhidade of the horizontal circle of the declinatorium, a horizontal 

 brass rod is fixed on each side, for the application of the vibrating magnet 

 as deflector. 



The apparatus is thus adapted for the observation of declination, hori- 

 zontal intensity, inclination and total intensity. The horizontal circle is fur- 

 nished with two verniers, which allow of direct reading to 0.5'; increasing 

 readings correspond to increasing easterly declination. 



As already mentioned, the constants of the apparatus were determined 

 in Hamburg, before its despatch, by a series of observations taken between 

 the 3rd and the 9th June, 1893, in the Compass observatory of the 'Deutsche 

 Seewarte' by Dr. NEUMAYER and Captain SCOTT-HANSEN together. Six months 

 after the return of the expedition, between the 2nd and 7th March, 1897, a 

 new set of constant-determinations was made by Captain SCOTT-HANSEN at 

 the same place; but as electricity had been introduced on the neighbouring 

 tram-line in the mean time, the value of the results of these observations is 

 somewhat doubtful. For the sake of certainty, therefore, the instrument was 

 taken to the Imperial Marine Observatory at Wilhelmshaven, where the 

 observatory assistant, Herr E. STUCK made a number of observations between 

 the 17th and 20th April, 1897. These observations show that the constants 

 of the apparatus were in the main unchanged from what they had been four 

 years before. 



The thermometers belonging to the apparatus were tested during the 

 expedition for the position of their zero, and occasionally also, for other 

 temperatures, compared with the other verified thermometers of the expedition, 

 some of which also were employed in the magnetic observations. All the 

 temperatures quoted in this paper are given in centigrade degrees, and cor- 

 rected for the error of the instrument; and they may be presumed to be 

 correct to within 0'1 or 0'2 C. 



An ordinary anchor escapement watch by Haagensen was generally used 

 in making the magnetic observations, and was constantly compared with the 

 standard watch of the expedition, the Hohwti chronometer. In determining the 

 time of oscillation of the magnetic needle, a Frodsham chronometer was 



1 Handbuch der nautischen Instrumente. Zweite Auflage. Berlin, 1890, p. 275. 



