370 AURORA BOREALIS. 



that some very important facts have been over- 

 looked, which, if known and rightly considered, 

 might place the whole subject in a new light. 

 It is to be hoped, that fifty years hence, we shall 

 have fifty accurate observers of natural pheno- 

 mena for one at the present time. 



Very little is known of the aurorse in the 

 southern hemisphere, except what has been 

 observed by Captains Cook and Weddel, who 

 relate that they have been frequently seen south 

 of Van Dieman's Land, and off Cape Horn, 

 where the cold is excessive.* 



* From a general view of the foregoing chapters, it must be 

 obvious : 



1. That all the phenomena of evaporation and rain, lightning 

 and winds, hurricanes and tornados, fluctuations of the baro- 

 meter, and formation of the aurorae, are immediately connected 

 with the theory of caloric, and those fundamental laws which 

 govern its distribution over our planet: 



2. That the aurora is a thermo-electric phenomenon, pro- 

 duced during the condensation of vapour contained in the equa- 

 torial upper current of the atmosphere, on its passage to the 

 polar latitudes, in a mode analogous to the evolution of lightning 

 from the more elastic vapour of the lower and denser atmosphere, 

 on mixing with colder currents, as during thunder storms. 



In opposition to this theory, it is maintained by Dr. Faraday 

 and others, that " the electric equilibrium of the atmosphere is 

 preserved by the aurora conveying electricity from the poles to 

 the equator." Can it be possible that the vast amount of light- 

 ning perpetually disengaged within the tropics, and during sum- 

 mer in the middle latitudes, is thus obtained ? With sentiments 

 of unaffected and profound humility, the preceding facts are 

 offered as an answer to this query. 



