fetRkELANb. THE NORWEGIAN AURORA SOLARIS EXPEDITION, 1902 1903. 



convergence. If we suppose that the principal axis of the system is always almost tangent to the 

 auroral zone, it corresponds exceedingly well with what one would expect. 



Chart II for j h 



j h jo' 



and /'' 45'", shows the conditions as they subsequently develope. 



We can here distinctly follow the movement described above. 



The storm-centre now is entering North America, and at the last two hours named it is perhaps 

 situated a little to the west of Hudson Bay; for it may be concluded from the arrows that the transverse 

 axis must pass between Sitka on the one side and the eastern stations on the other. 



The force at Dyrafjord in the mean while has decreased considerably, showing that the storm- 

 centre has moved away. At Axeleen, too, the forces are considerably less than before. 



We thus have in this perturbation an instance of a polar elementary storm that occurs at a different 

 time of day, and has a somewhat different course, from those described previously. There may, more- 

 over, possibly be other perturbing forces in Europe. The declination-curve for Stonyhurst, wich we 

 have, points indeed in this direction; but we have not the material to enable us to study this more 

 closely. We have therefore not included this among the elementary storms. 



The movement of the system in America that we have here met with, will be also investigated 

 more throughly in the material from 1882 83; and we shall there find similar conditions during nearly 

 all the perturbations that occur in this region at about this time of day. 



TABLE XXV 

 The Perturbing Forces on the z8th December, 1902. 





TABLE XXV (continued). 



