AURORA BOREALIS. 365 



across the firmament, which breaks up into 

 columns or streamers that extend towards the 

 zenith. 



Various conjectures have been offered in re- 

 gard to the height at which the aurorae are 

 formed, nearly all of which have been founded 

 on imaginary data. For example, some philo- 

 sophers have supposed that they must be formed 

 at a great elevation, because they have been 

 seen at the same time in very distant countries, 

 as England and America. But it would be quite 

 as reasonable to conclude, that ordinary light- 

 ning is given off at a great elevation, because it 

 lightened at the same time in England and 

 America. There is no rational ground for sup- 

 posing, that the aurorae are formed above our 

 atmosphere ; and probably never beyond a few 

 miles, while there is every reason to believe, 

 that they may be formed in hundreds of places 

 over different parts of the earth at the same time. 



It was the opinion of Franklin, Parry, Ross, 

 Hood, and Dr. Richardson, that the auroras of 

 the arctic regions were frequently not higher 

 than ordinary clouds and Dr. Richardson 

 thinks that they are always attended with the 

 formation of clouds, or of that kind of haziness 

 which causes a halo around the moon a very 

 important fact, which would seem to establish 

 their connexion with the condensation of aque- 

 ous vapour, as suggested by Dr. Franklin. 



