PREFACE. 



1 he knowledge gained, since 1896, in radio-activity has favoured the view to which I gave 

 expression in that year, namely, that magnetic disturbances on the earth, and aurora borealis, are 

 due to corpuscular rays emitted by the sun. 



During the period from 1896 to 1903 I carried out, in all, three expeditions to the polar 

 regions for the purpose of procuring material that might further confirm this opinion. I have 

 moreover, during the last ten years, by the aid of numerous experimental investigations, endea- 

 voured to form a theory that should explain the origin of these phenomena. It is the results of 

 these investigations that are recorded in this work, the first volume of which treats of terrestrial 

 magnetic phenomena and earth-currents, this section forming the first two thirds of the volume. 

 The second volume will treat of aurora and some results of meteorological observations made at 

 our stations. 



The leading principle that I have followed in this work has been to endeavour always to 

 interpret the results of the worked-up terrestrial-magnetic observations, and the observations of 

 aurora, upon the basis of my above-mentioned theory. 



Thus the magnetic storms, for instance, have been studied in such a manner, that on the 

 one hand we have formed from our observation-material a field of force which gives as complete 

 a representation as possible of the perturbing forces existing on the earth at the times under 

 consideration. On the other hand, by experimental investigations with a little magnetic terrella 

 in a large discharge-tube, and by mathematical analysis, we have endeavoured to prove that a current 

 of electric corpuscles from the sun would give rise to precipitation upon the earth, the magnetic 

 effect of which agrees well with the magnetic field of force that was found by the observations 

 on the earth. 



Although our observation-material of magnetic storms was, I may safely say, the largest that 

 has ever been dealt with at one time, it was deficient in certain points, as might well be expected. 



We generally had at our disposal in 1902 1903, magnetic registerings from 25 observatories 

 scattered all over the world, among them being our 4 Norwegian stations on Iceland, Spitsbergen, 

 Novaja Semlja, and in Finmark. 



We have moreover treated separately certain well-marked magnetic storms in 18821883, 

 from the observations in the reports of the international polar expeditions. 



In addition to the deficiencies in our observation-material, there are also defects in the 

 experimental and mathematical investigations; but notwithstanding all this, the results are so 

 satisfactory that I can hardly be mistaken in my belief that we are on the right road. 



