PART I. ON MAGNETIC STORMS. CHAP. HI. 



elementary storms, both with fairly simple course. The table above gives the time at which the two 

 perturbations begin, attain a maximum, and end, and the value of P t at its maximum. We find here a 

 distinct confirmation of the statement that the effect of the force diminishes from the poles to the equator. 



The table shows that the two perturbations differ essentially as regards distribution of strength. 

 Although the first storm is less powerful at the Norwegian stations, and rather less powerful in Central 

 Europe, it is nevertheless somewhat more powerful than the second when we come nearer to equator. 

 There is a still greater difference with regard to the conditions in America, the first storm being 

 almost imperceptible there. ' 



We thus receive a decided impression that the current-system that conditions the field however 

 this may be constituted in the second storm is situated, on the whole, farther west, a circumstance that 

 may to some extent explain the different distribution of strength in the two storms. 



THE FIELD OF FORCE. 



64. The field during the first storm is in the main of the same form and relative strength as in 

 the intermediate storm on the 27th, but less powerful. The current-arrows in the north are directed 

 westwards along the auroral zone, and the effect is strongest at Axeleen and Matotchkin Schar. 

 P, at Kaafjord and Matotchkin Schar is directed downwards, at Axeleen upwards. There is an area 

 of convergence with a fairly strong force in the eastern hemisphere, but an area of divergence with 

 comparatively little force in the western. The point of convergence is situated in the regions round 

 the north-east of Russia. The field, at those places from which we have observations, is almost 

 stationary. At Pawlowsk, P, is directed upwards. 



The field during the second storm is almost exactly the same as that during the second storm on the 

 previous day. All that has been said of the field on the 2yth may be directly applied to this perturbation. 



As on the previous day, there is a movement of the system towards the east. This is evident, 

 both from the clockwise turning of the arrows in the south of Europe, and from the conditions at the 

 Norwegian stations. If we look at the current-arrows for Axeleen and Kaafjord, we see that they are 

 at first convergent, showing that the storm-centre is to the west of those stations. When the storm is 

 almost at its height, they become parallel, and end by being Divergent, thus indicating the eastward 

 position of the storm-centre. 



These two storms, as we see, are the very ones to afford favorable conditions for a determination 

 of the strength of the horizontal portion of the current, and such a calculation will therefore be made. 



The very interesting systems of current-arrows are shown on the Charts I to VII. 



TABLE XXXVI. 

 The Perturbing Forces on the 28th October, 1902. 



