1'ART I. ON MAGNETIC STORMS. CHAPT. I. 



53 



DETERMINATIONS OF SENSIBILITY FOR AXEL0EN. 



20. The registering apparatuses on Axeleen were in operation from the 3oth August, 1902, without 

 interruption until the yth June, 1903. 



Neither the variometer for the horizontal intensity, the declinometer, nor the balance were changed 

 during that time. 



No determinations of sensibility were made on Axeleen for the variometer for the vertical intensity, 

 as this apparatus was without deflection rods. The position of the movable parts of the magnet, and the 

 arrangement of the balance, were however accurately noted. 



Determinations of sensibility were made at the Physical Institute, ? A 



Christiania, after the return of the Expedition, the conditions 

 that had prevailed on Axeleen being reproduced as exactly as 



possible. No alteration in the magnetic moment is to be "%? 



apprehended, as the magnet was several years old. The balance- ^^^ .. t 



magnet was of the form shown in the figure. The movable > EE? J=E ^,1 



parts consist of a small weight B, which can be screwed back- ~~ ^*~" 



wards and forwards along a small, horizontal, brass rod, and a Fig. 28. 



weight A, capable of being moved in a vertical direction. 



By moving B, the magnet can be adjusted horizontally. It is easy to see that a small change in B will 



have no great influence upon the sensitiveness, as the centre of gravity of the system is neither raised 



nor lowered thereby to any noticeable extent. By screwing A, on the other hand, the sensitiveness is 



altered, as the height of the centre of gravity is thereby altered. 



As the position of A is not so easy to find again accurately, two determinations were made, the 

 weight A being placed in the highest and lowest positions possible in the case in question. 



The determinations gave the following result: 



A in lower position 



A in upper position 



( Distance of deflecting magnet 56.4 cm. = 25.6 



\ 



47-05 



= 24.9 



Mean = 25.25 

 Distance of deflecting magnet 47.05 cm. t v = 23.85 



Mean = 24.6 y 

 As we use the mean value, the error should not exceed 4 per cent. 



TABLE V. 



Scale- values for Axeleen 

 HO =0.0941 rrf = i733mm. -/ = 0.0079 



= 2.736 



