THE SIDEREAL UNIVEKSE. 763 



regions during the long nights of winter, a phenomenon 

 known as the Aurora Borealis or Austrahs. 



Whilst this lasts the heavens sometimes present the 

 most splendid spectacle. On the black and starry back- 

 ground of the sky we see traced out a vast luminous 

 cupola, or kind of panelled vault, formed of colonnades of 

 stalactites heaped together and pendant, and which sus- 

 pended in the clouds reflect the brightest hues of the 

 rainbow. Sometimes they resemble fireworks which dart 

 their sheets of flame in every direction, and seem to set 

 on fire the horizon, forming one of the most imposing 

 spectacles it is possible to enjoy amid the ice of the north. 



