THE AURORA BOREALIS 93 



phere they electrify the molecules of the gases neon, 

 argon, etc., and cause them to phosphoresce and 

 produce the light known as the aurora borealis. 



In brief, the aurora borealis is due to the 

 bombardment of the rarefied gases of the outer 

 atmosphere by electrons ejected by the sun, and 

 borne across space by light pressure. 



The theory is surely beautiful. We believed 

 that the light gases were probably at the top of 

 the atmosphere, but no one had ever been there to 

 see, and lo ! we find that the sun pelts them with 

 electrons across ninety-three million miles of space, 

 and compels them to sign their names through 

 Lockyer's spectroscope. We had reason to believe 

 that electrons were emitted by the sun ; we had 

 reason, from Clerk-Maxwell's calculations, and 

 from Peter Lebedew's experiments, to believe that 

 the electrons of the sun would be carried across 

 space by the pressure of light ; but we had no 

 proofs of the correctness of our beliefs, and lo ! we 

 find in the red and green of the Northern Lights 

 proofs almost indubitable. Again, we had every 

 reason to believe that the earth is a great magnet, 

 with lines of force curving through space ; but 

 what proof of it have we here when we see the 

 electrons arranged by its lines of force, even as 

 iron filings are arranged according to the lines of 

 force of an ordinary little magnet ! 



