POLAR LIGHT, OB AURORA. 187 



On the other hand, all the three manifestations of terrestrial 

 magnetism, the declination, inclination, and force, are affected 

 during the appearance of the polar light ; so that in the 

 course of the same night, and during different parts of the 

 phsenomenon, the same end of the needle is sometimes 

 attracted and sometimes repelled. The statement that the 

 facts collected by Parry in Melville Island, in a high mag- 

 netic latitude, indicated rather a tranquillizing than a 

 disturbing influence of Auroras upon the magnet, has been 

 refuted by a more careful examination of Parry's own 

 journal, ( 178 ) by the valuable observations of Richardson, 

 Hood, and Franklin, and latterly by Bravais and Lottin 

 in Lapland. As I have before remarked, the luminous 

 phenomenon is the act of restoration of equilibrium 

 temporarily disturbed ; the effect on the needle varies with 

 the intensity of the discharge; at the winter station 

 of Bosekop it was always sensible, except when the 

 luminous phsenomenon was very faint, and appeared only 

 low down near the horizon. The Auroral streamers 

 have been ingeniously compared to the light which, in 

 the Voltaic circuit, is produced between two points of 

 carbon placed at a considerable distance from each other, 

 (or, according to Eizeau, between a point of carbon and 

 one of silver) ; a light which is attracted or repelled by the 

 magnet. This analogy renders superfluous the assump- 

 tion of metallic vapours in the atmosphere, which some 

 celebrated physicists have considered to be the substratum 

 of the Aurora. 



In applying to the luminous phsenomenon which we 

 ascribe to a galvanic current the vague term of polar light, 

 or Aurora borealis and australis, we merely indicate thereby 



