PART I. ON MAGNETIC STORMS. CHAP. II. 115 



researches on the storms of 188283 in the polar regions (Part II), we shall also sometimes find a field 

 on the other side of the auroral zone, that appears to indicate an area of divergence, at the same time 

 as the forces in the southern parts of Europe form an area of convergence. 



This fully explains a circumstance mentioned in the description of the first part of the perturbation, 

 namely that Pawlowsk has a very small horizontal component considering the northerly situation of the 

 place. During the beginning of the perturbation, the direction of the current-arrow is almost the reverse 

 of that of the horizontal portion of the current. During that time therefore, the station ought to lie 

 nearer to the neutral district than later, when, owing to the movement of the system, the perturbing 

 force is turned more in accordance with the conditions in Central Europe. 



In this perturbation also, the vertical components are very small in the regions outside the arctic 

 district, a circumstance that accords perfectly, as we have already said, with our explanation of the 

 perturbation, as those components should mainly be conditioned by the horizontal portion of the current. 

 In the vicinity of the neutral district, P, only should be of considerable size in proportion to /*,. At 

 Pawlowsk there is actually a considerable vertical component directed upwards all the time. In the 

 cases of Potsdam and Pola, it is much smaller, but directed upwards; and at Val Joyeux it is almost im- 

 perceptible. 



THE PERTURBATIONS OF THE 30th & 31st MARCH, 1903. 



(PI. XXI). 



40. For the study of these perturbations, we have magnetograms for the horizontal intensity and 

 declination from all the stations marked on the chart with the exception of Matotchkin Schar, where, on 

 that day, the registering apparatuses were not acting. The declination-curve for Bombay is also wanting. 

 The observations from Ekaterinburg and Irkutsk are only for every hour; and as the perturbation is 

 short, there will here be little use in taking out intermediate values. 



At Bossekop, the needle in the variometer for horizontal intensity during the perturbation was 

 deflected out of the field, and did not return. The perturbing force here can only be taken for the first 

 part of the perturbation. 



In addition to the horizontal intensity and declination curves, there are also vertical intensity curves 

 for the Norwegian and some other stations. 



The time during which this violent perturbation is acting at the Norwegian stations is very short.' 

 The deflections, moreover, are uniform in direction. The character of the curve in the north is as usual 

 very disturbed, and varies greatly from place to place, indicating that the current-systems that condition 

 the phenomenon here, must come comparatively near the earth. 



Simultaneously with this exceedingly powerful, brief storm round the Norwegian stations, distinct 

 perturbations are noticed at all the observatories from which observations have been received. The 

 curves immediately show that the perturbations outside the arctic district are of a universal character, as 

 the form of the curve remains very nearly constant over large districts, and the transition takes place 

 gradually - - conditions with which we meet in most of the polar storms. 



It will be seen from the magnetograms from the districts visited by this perturbation, that in advance 

 of this elementary storm in the north, there is a long perturbation that is especially powerful and distinct 

 at the stations near the equator, and occurs chiefly in H. We also note the jagged character of the 

 curve, and that the serrations occur simultaneously all over the earth. That the perturbation between 

 24'' and 2 h is connected with that in the north is probable from the fact that it then rather suddenly 

 becomes comparatively powerful in D, and also that the horizontal intensity curve oscillates greatly at 

 this time. The perturbation moreover becomes more powerful with an approach to the northern stations. 



