252 



Marvels of the Universe 



According to the latest 

 \-ie\vs, the Northern Lights 

 waves are negative electric 

 rays which the sun, and especi- 

 allv the solar spots, send out 

 into space. These are what 

 are called " kathode " rays. 

 They bear a strong resemblance 

 to radium rays, and may there- 

 fore be regarded as a kind of 

 immense electrons. It has long 

 been known that these rays are 

 closely connected with the sun- 

 spots, as we find in both 

 the same eleven-year periods. 

 ^Vhen a ray of this kind comes 

 into the neighbourhood of a 

 magnetic expanse, as, for in- 

 stance, on the earth in the 

 vicinit}' of the magnetic pole, 

 the ray will be, so to speak, 

 sucked up by it, as Birkeland 

 expresses it. If the course of 

 the ra}'-, on the other hand, is 

 not directed towards such an 

 expanse, it will be diverted 

 from its course, and in this 

 wa\" the most varied forms 

 arise. As our earth is \"ery 

 small in comparison with the 

 universe, great expanses may 

 very well be affected at the 

 same time by the magnetic 

 disturbances, and Birkeland 

 has discovered, by placing in- 

 struments at Potsdam and Bosekop in the north of Norway, that the variations in the magnetic 

 elements were alike at the two places at the same time, onh' that the oscillations were more 

 intense in. Norway. 



The Aurora Borealis causes magnetic disturbances which are called magnetic storms. The 

 theory has been propounded that the earth derives its magnetism from the Northern Lights. 



We owe to Professor Stormer the mathematical calculation of the course of the rays and of 

 their length — a portion of the subject in which the French scientist, Poincarre, has also done good 

 service. 



In one of his experiments which consisted in passing an electric current through a bottle filled 

 with rarefied air, Birkeland has produced light-waves (corkscrews) similar to what ma}- sometimes 

 be seen in the Aurora Borealis. 



The Northern I..ights reach our atmosphere, but onlv the more rarefied upper air. They have 

 the property of condensing aqueous vapour, and there are clouds whose origin is attributed to the 

 Northern Lights. At the South Pole there exists a similar light, called the Aurora Australis. 



[/In Mu.l llneh,-t. 



NORTHERN LIGHTS. 



These were formerly thought to foretell a hard frost, but M. Raebel's observations 

 lead him to quite the opposi te conclusion ■ in most cases milder \veather follows 

 immediately after a display. 



