PART I. ON MAGNETIC STORMS. CHAP. II. 125 



Chart I. Time o 1 ' //'" . 



In the regions nearest to the equator, the current-arrow points from E to W, while in Central and 

 Southern Europe it has a more southerly direction. 



The northernmost stations differ greatly in this respect, the conditions at Kaafjord, in particular, 

 being quite peculiar. If the perturbation really has attained to such magnitude by this time, it must be 

 the result of purely local occurrences, or rather, the effect must be so strong on account of the proximity 

 to the currents that bring about the phenomenon. 



Leaving the most northerly stations out of consideration, the force is strongest at the equator. 

 From this we may conclude that we still, at this hour, have to a great extent the effect of the previ- 

 ously-mentioned equatorial perturbation, which commenced at 23** I2 m , and which had a current-system 

 the reverse of that shown on the chart for 22 h o m . 



In the period under consideration, what we are concerned with is thus a slight equatorial pertur- 

 bation together with the incipient polar storm. 



Chart II. Time o h jo m . 



The effect of the polar storm is now altogether predominant. In Europe the current-arrows have 

 already reached their maximum by this time. The directions of the arrows in Europe and the United 

 States show distinctly that the field of force for the horizontal component has a point of convergence 

 that is situated somewhere in the North Atlantic, probably a little south of the point of Greenland. 

 There, according to our assumption with regard to the cause of these perturbations, the horizontal force 

 should equal 0. We notice also the direction of the current-arrows at Toronto and in the United States, 

 converging as they do to a point in the north of Labrador. 



On the whole we may say that outwards the field is explained by the assumption that the current 

 with negative particles descends towards the earth in the direction of the north of Labrador. It then 

 turns off almost along the auroral zone, and leaves the earth in the district between the southern point 

 of Greenland and Iceland. Judging from the form of the outer field of force, the current-system should 

 have its centre at the southern point of Greenland, or a little to the west of it. 



If we look at the conditions in the vertical intensity, we should expect, if this were the only 

 system, to find P, negative at all the stations in Europe and Asia, or possibly zero at certain places. 

 On the contrary, however, we find that at several places there are positive values of P v , e. g. at Pots- 

 dam, Val Joyeux and Tiflis; while at Pola and Wilhelmshaven they are in the opposite direction. The 

 conditions at Bossekop, moreover, at these hours, are rather peculiar in the two components that we 

 have ; for just before, these two turn round in the opposite direction, and P d remains for a time in a 

 westerly direction, and P, for a shorter time positive. This opposite deflection takes place slightly 

 * earlier in the vertical intensity than in the declination. The forces otherwise are so strong that they can 

 hardly be explained by this system alone. Other perturbing causes seem to assert themselves, but of 

 what kind it is impossible to determine, as nothing can be concluded as to the conditions in the horizon- 

 tal intensity. It is possible that these two circumstances are connected with one another ; but as we have 

 said, the data necessary for the determination of this question are wanting. 



Chart III. Time o h 45. 



The storm has now also become powerful at Axeleen, in fact it is at its height. The arrows in 

 the western hemisphere are about the same in direction and size as in the preceding chart. The arrows in 

 Europe, on the other hand, have made quite a considerable turn clockwise. The perturbing forces at 

 Dyrafjord and at the stations in England, Germany and France, have the reverse direction, and point 

 downwards towards the same point. The central point of the system must thus be situated somewhere 



