324 BIRKELAND. THE NORWEGIAN AURORA POLARIS EXPEDITION, 19021903. 



and finally positive values once more. It seems evident that we here have before us the effects of a 

 negative storm, which during the interval from ia h to I4 h , encroaches upon a positive storm of longer 

 duration, and that from 12'' 50 to 13^ 50 the effect of this negative storm is the strongest, so that 

 negative values of PI, are found. This view seems to receive support from the conditions in declination, 

 where, from I2 h to I4 h , there occurs a clearly defined deflection. 



If we continue to follow the series of polar stations, we find during this period practically no per- 

 turbation at Bossekop and Sodankyla, nor is there any deflection in Jan Mayen until the end of the 

 period under consideration, when a new positive storm begins there, with a very well-formed and 

 clearly-defined deflection, during the period from 13'' to 16'' 4o m . The defining of the first section, which 

 we have previously undertaken, is thus not suitable for this station. 



At Fort Conger also, there occurs a deflection which bears no small resemblance to the deflection 

 in the horizontal-intensity curve in Kingua Fjord; only in this case the perturbing forces are small. At 

 the southern stations there are no perturbing forces of any strength during this period. 



It may be as well here, in connection with these conditions, which are read directly from the 

 copies of the curves, to consider at once the area of perturbation, as represented in Chart I and II 

 for the hours //'' 2o m , u 1 ' jo m , I2 k 20, 12*' jo"' and ij h 2o m , Gr. M. T. 



The two characteristic areas of precipitation described above, the negative in the north of America, 

 and the positive in the north of Asia and to some extent also in Europe, are here very distinctly seen. 

 At first it is only the negative system that has a marked effect, and its storm-centre appears to be 

 situated in the vicinity of Fort Rae. At Uglaamie, during this first part of the time, the current-arrow 

 has an easterly direction, the reverse of that which we find subsequently. It is as though we had before 

 us the effects of a positive polar storm, and this may possibly be the case; but if so, it is very ill- 

 defined, and this makes it impossible to decide the question with any certainty. At the succeeding hours 

 moreover the current-arrow at this station swings round anti-clockwise, and remains directed westwards 

 during the remainder of this first section which we are now considering. We may perhaps be justified 

 in taking these conditions as a proof of a movement of the systems of precipitation in a westerly direction. 



At the other stations situated in the vicinity of the areas of precipitation, the current-arrows 

 increase more or less evenly, so that at the last of the hours of observation they attain their greatest 

 strength, and the areas undergo no great changes. A quite distinct impression of a westerly movement 

 in the positive precipitation area will be obtained by comparing the Chart II for I2 h 30 with the two 

 last times on Chart I. On Chart I I2 h 2o m it is only at Ssagastyr that the positive storm occurs with 

 considerable violence, in Little Karmakul the perturbating force is still comparatively insignificant. At 

 I2 h 5o m , on Chart II, also in Little Karmakul, a somewhat powerful perturbating force occurs. The 

 strength is, however, as yet greatest in Ssagastyr, but at 13'* 2o m , as we see from Chart I, the 

 strength of the perturbing forces is about equal at these two stations. The centre of the storm seems 

 thus constantly to move westwards. 



At Cape Thordsen only do we see the current-arrow turning clockwise in accordance with the 

 peculiar conditions that we have just described. 



According to what we have seen in Part I, the positive polar storm will now, in lower latitudes, 

 produce an area of divergence. 



With regard to the conditions in lower latitudes, we find only small perturbing forces at the first 

 three hours of observation; but at 13'' 2o m , the forces have increased to no small extent; and the shape 

 of the western portion of an area of divergence is now actually recognised. 



We will finally also draw attention to the agreement that we find between this and our previous 

 results, namely, that the negative area of precipitation is formed upon the night and morning side, while 

 the positive system is formed upon the afternoon and evening side. 



