PART II. POLAR MAGNETIC PHENOMENA AND TERRELLA EXPERIMENTS. CHAP. I. 373 



We can thus, in this district from Kingua Fjord, or at any rate from Fort Rae, through North 

 America to Ssagastyr, trace a distinct westward movement of the system of precipitation. A powerful 

 but not extensive system first developes in the vicinity of Kingua Fjord, and apparently spreads towards 

 the west and forms the great, connected system of precipitation in the north of America, presumably 

 simultaneously with the westward movement of the entire system with the sun. 



No specially pronounced movement is descernible, on the other hand, in the positive system. It 

 might appear, indeed on a cursory glance at the deflections in Jan Mayen as compared with those at 

 Bossekop and Sodankyla, as if there were a distinct eastward movement of the system ; for at about I4 h 

 20 the positive deflections at the first-named station attain a considerable strength, and remain more or 

 less constant until 16'', when they once more diminish rapidly. At Bossekop and Sodankyla, the positive 

 deflections begin at about the same time as those in Jan Mayen ; but they increase slowly, and the most 

 powerful forces are not found until between i6 h 30 and 17'' 30, the time at which the conditions in 

 H in Jan Mayen are fairly normal. It might thus appear as if the positive system had here moved 

 eastwards; but we have already explained the way in which this phenomenon is to be understood, and 

 how the negative system to the north breaks in upon the positive system first acting in Jan Mayen. 

 This, however, does not preclude a possibly eastward movement of the system of precipitation. It is 

 also probable that the positive storm-centre will be moved; but the observations we possess do not afford 

 sufficient evidence of this. 



Little Karmakul is now also upon the border between the two systems of precipitation ; and its 

 curves have consequently the disturbed, jagged character so often observed before. At one time the 

 positive system is the stronger, at another the negative, although at first the positive system predomi- 

 nates, while from about I7 U 30 onwards, the effect of the negative system is the more apparent. 



The negative storm at Cape Thordsen and Fort Conger must on the whole be regarded as a con- 

 tinuation of the negative storm in North America and the north-east of Asia, although it is very possible 

 that it forms a more independent system. 



At the southern stations it is sometimes rather difficult to determine the normal line, as the diurnal 

 variation at this season of the year is considerable, and the data from which the determination is made 

 are as a rule few. It is therefore possible that some error will attach to the values found; but at the 

 times when the perturbing forces are powerful, this will have no great signifiance. 



At about 2o h , this perturbation is practically over. This is clearly apparent from the curves of the 

 horizontal intensity. It is not yet quiet everywhere, however, as, in the declination especially, there are 

 sometimes fairly powerful perturbing forces. 



In the district Fort Conger to Kingua Fjord, the effects of a fairly powerful system of precipitation 

 are still distinctly apparent, and are noticeable at Godthaab and to some extent in Jan Mayen. The 

 perturbation is especially powerful at Kingua Fjord. At about 23*", however, new storms begin to 

 develope, evolving in the usual manner of the polar storms at about midnight, Greenwich time. A 

 powerful negative storm on the night-side, from Little Karmakul, across Bossekop to Jan Mayen, forms 

 the main system, its effect also extending westwards across Ssagastyr to Uglaamie. We find moreover 

 distinct traces of a positive system on the afternoon-side, especially at Fort Rae; but the horizontal- 

 intensity curve for Godthaab and possibly Kingua Fjord indicates that these stations are also affected 

 by this positive system. Here, however, the conditions seem to be rather more complicated, perhaps 

 because the effects of the above-mentioned system occurring in these regions are still apparent. 



Special attention should be paid to the positive system of precipitation on the afternoon-side in 

 North America. It occurs principally at Fort Rae, that is to say it is most marked at the station situated 

 to the south of the auroral zone. 



Birkeland. The Norwegian Aurora Polaris Expedition 19021903. 48 



