152 NORTHERN LIGHTS. [LffSSOn XXIV. 



be a fianie arising from a chemical effervescence of 

 combustible exhalations from the earth. 2. It has 

 been thought lo be inflammable air, fired by elec- 

 tricity. 3. It has been imagined to be occasioned 

 by the zodiacal light. 4. It has been conjectured, 

 that it is caused by the reflection of the sun's 

 beams on large bodies of ice floating near the po- 

 lar regions. But all these suppositions will admit 

 t)f objections, being utterly inadequate to account 

 .for the appearances. Lastly, it has been supposed 

 electric light itself; and this opinion has met with 

 many advocates since the identity of lightning and 

 the electric matter has been determined : for we 

 know that discharges of the electric fluid in the 

 atmosphere do exhibit light; and for this, and other 

 reasons which might be advanced, it is considered 

 almost beyond a doubt, that the light of the Au- 

 rora Borealisas-we]] as \hatof falling stars, and the 

 large meteors, is electric light solely, and that there 

 is nothing of combustion in any of these phae- 

 nomena. 



M. Libes has lately proposed a new theory of the 

 Aurora Borealis, which has already been adopted 

 by most of the northern philosophers, and may be 

 concisely stated thus : the production of hydro- 

 genous gas is next to nothing at the poles ; there- 

 tore, so often as the electricity is put into an equi- 

 librated state in the atmosphere, the spark, instead 

 of passing through a mixture of hydrogenous and 

 oxygenous gas, as in our climates, passes through 

 a mixture of oxygenous and azotic gas : it must 

 therefore cause a production of nitrous gas, nitrous 



acid, 



