PART II. POLAR MAGNETIC PHENOMENA AND TERRELI.A EXPERIMENTS. CHAP. I. 



365 



The direction of the current-arrow at Little Karmakul on Chart IV might be explained by the cir- 

 cumstance that the station was situated in the area of convergence of the negative system of precipita- 

 tion, and south of the point of convergence; but a consideration of the course of the curve seems to 

 make such an assumption at any rate very improbable, as the forces are much too strong, and the char- 

 acter of the curve too disturbed. These conditions seem to indicate more or less certainly that we have 

 before us the effects of a positive precipitation. 



The fact that it is difficult to follow the movement of the system in the polar regions, may to some 

 extent be due to our lack of observations for the time about the beginning of the perturbations. 



If we assume that the negative district of precipitation continues also in the districts to the east- 

 ward of Europe as indicated above, we have a good explanation of the perturbation-area that appears on 

 Chart IV. If, on the other hand, we assume that it terminates somewhat to the west of Little Karmakul, it 

 will be much more difficult to find a simple explanation of that, supposing the storm to be more or less 

 purely polar. Altogether it is difficult to say anything more definite about the conditions here, as the 

 observations supply only very imperfect information regarding the perturbation-conditions. 



On Chart V we see however that the positive system in Little Karmakul, which hitherto have not 

 been very prominent and which on the whole would appear to have been of mainly local character, 

 begins to assert itself more strongly. Simultaneously with this, the traces of converging area, which 

 we up to Chart IV find at the southerly stations, disappear. 



On Chart VI the negative system in the north of Europe has disappeared, but on the other hand 

 we now find the previously mentioned system at Godthaab very well developed. At Fort Rae the posi- 

 tive polar storm also begins to develope, although the forces there are still very weak. 



Lastly, on Chart VII, for 2'' I5 m , the positive system at Fort Rae has attained a more or less con- 

 siderable magnitude. We find moreover a negative storm that is only slight, though very distinct; and 

 on each side of the principal axis; the two characteristic areas of convergence and divergence seem to 

 be formed here too. 



Subsequently the positive storm at Fort Rae deyelopes further, and attains its greatest strength at 

 about 3''. As, however, at this hour, there are no perturbations of any great strength at the other 

 stations, we have drawn no chart. 



TABLE LIV. 

 The Perturbation of the i4th & I5th February, 1883. 



(') Great variation in temperature, which has a great influence on the form of the normal line. 

 Birkeland. The Norwegian Aurora Polaris Expedition, 1902 1903. 47 



