20 



KR. BIRKELAND. 



M.-N. Kl. 



I shall only refer to figure 254 for the case of rays emerging far 

 away from the magnetic cathode-sphere. In this case the magnetisation is 

 small or the rays are very stift". 



For the other case when the magnetisation is strong, we have the 

 Saturn ring phenomena figure 255 c and figure 257. The thick light ring 

 round the cathode-glohe seen in fig. 248 b and c is also most interesting; 

 here the discharge current is great. 



When the magnetisation of the cathode-sphere is augmenting, we 

 arrive at a given magnetic intensity of a sudden change from phenomena 

 of the first kind to phenomena of the othei" kind. The experiment here 

 then full}' corresponds to the thef)rv. 



I'ig. 4. The ne-bula in X'irgo. 

 N G C. 4594- 



Fig. 5. Tlie nebula in Aquarius. 

 N. G. C. 7009. 



It is also easy to find photographs from nebulae that seem to show 

 these two classes of ray-emanation fiom the central body ^ 



The nebula in Virgo N. G. C. 4594 represented above, fig. 4 seems 

 to indicate emanation of cathode and atom-rays, radiant matter, of high 

 magnetic stiffness, or radiation from a weak magnetic central body. 



The dark rift in the nebula is very remarkable for it is seen in many 

 other nebulae which stand edgeways to the earth. 



The dark rift can be reasonably assumed to be due to screen effect 

 of a great multitude of cooled material particles which have arrived out- 

 side the electro-magnetic piienomena. The latter have already retired 

 somewhat and concentrated towards the matter-radiating central body, 

 acting as cathode. 



The nebula in Aquarius N. G. C. 7009 fig. 5 seems to give an 

 example of ray-emanation of the second class, where the magnetisation of 

 the radiating sphere is relatively great, or the rays mays be more flexible. 



The photographs of these two nebulae were taken at Helwan Obser- 

 vatory, and the director has been kind enough to allow me to reproduce them. 



1 .See my paper „De l'origine des mondes" I. c. 



