KR. BIRKELAND. M.-N. Kl. 



watt lamp of 300 candles furnished the light necessary for the registration. 

 Very often such curves were rather smooth, but perhaps more frequently 

 they are more or less disturbed, and even considerably more than in the 

 curve reproduced. 



Sometimes the light intensity curve had some resemblance to a simul- 

 taneously registered magnetic horizontal intensity curve, but more frequently 

 there was no resemblance. This is easily understood, seeing that the part 

 of the ray-disc round the sun, which we are studying with the photo-cell, 

 is quite a different part from that which contains rays proceeding towards 

 the earth causing magnetic perturbations. These oscillations registered 

 photographically in the zodiacal light call to mind the master observer of 



7b ipm 8h 8b 35m 



Fig. I. Registered light intensity curve for Zodiacal light. 



this phenomenon, Rev. George Jones, who published his chief results in 

 the third volume of »Report on the United States Japan Expedition« 1856. 

 His sharp eye first established with certainty oscillations in the zodiacal 

 light, and I therefore propose to call these oscillations »Jones Oscillations«. 

 They are of the highest theoretical importance, for there can be no doubt 

 that such oscillations point to the electrical nature of the phenomenon, 

 which gives off the faint light which we call the Zodiacal light. Now 

 I have by experimental analogies clearly proved the possibility of the 

 physical existence of such a ray-disc round the sun as my theories on 

 zodiacal light presuppose. 



The suggestive experiments figured pp. 667 and 669 in »Aurora 

 Polaris« provide a sufficient illustration, but here I also reproduce a good 

 photograph from a later experiment of the same kind. 



Figure 2. It is seen how round the magnetic sphere, which serves 

 as a cathode, there is formed a lamina of rays in the plane of the mag- 

 netic equator of the sphere. A similar lamina, but of immense size, is 

 what I suppose to exist round the sun, rotating with it, on account of its 



