THE AURORA BOREALIS 225 



would certainly remain gaseous ; for in order to liquefy or 

 solidify a gas, not merely reduction of temperature, but 

 also considerable pressure, is required. It is, however, 

 quite possible that water-vapour, in the lower regions 

 frequented by the aurora, may exist in a supersaturated 

 condition, and that the electric discharges may bring 

 about condensation, and on the large scale of nature, as 

 on the small scale of a laboratory experiment, produce 

 mists, and so give rise to the cirro-cumulus clouds which 

 so often accompany an aurora. 



The solving of conundrums has for many people a great 

 attraction; Nature surrounds us with conundrums, and 

 it is one of the greatest pleasures in life to attempt 

 their solution. Whether or not I have been successful 

 in offering a partial solution of the one which we may 

 call the ' Merry Dancers,' time will show. 



