Aurora Borealis. 



The Northern Lights constitute one of the clearest 

 proofs of the exchange of matter between the Sun and 

 the Earth. This phenomenon never presents itself in 

 presence of a barometrical minimum but always at times 

 of atmospherical maximum. The radiant crown which 

 sometimes shows itself never gives out rising sparks, 

 but is always formed of stout lines of light which rise 

 and fall like the water in the tubes attached to steam- 

 boilers for measurement of pressure. In time of the 

 Aurora Borealis a dark segment appears in the North, 

 rising much higher above the horizon on the East than 

 on the western side. 



In our text-books ot Cosmography these Northern 

 Lights are considered as an inexplicable natural pheno- 

 menon, but keeping in mind the fact that, like thunder 

 and lightning, they produce magnetic disturbance, the 

 idea naturally suggests itself that between these pheno- 

 mena there is something in common. We must remember 

 also that the so-called Northern light is also seen in the 

 southern sky, having been remarked there amongst others 

 by the celebrated scientist Humboldt. The majority of 

 physical geographies ascribe both storms and the Aurora 

 Borealis to local excess of accumulated atmospherical 

 electricity, which is supposed to produce in tropical and 

 moderate climes the former, and in polar regions the 

 latter effect. But this tells us very little from a scien- 

 tific point of view. 



If we closely examine the symptoms and results of 

 this luminous appearance, we shall come to the conclu- 



