TOLAR LIGHT. 151 



in the form of polar bands, correspond, according to the abovo 

 developed views, in respect to position, with the luminous 

 columns or bundles of rays which ascend in the true aurora 

 toward the zenith from the arch, which is generally inclined 

 in an cast and Avest direction ; and they can not, therefore, 

 be confounded with those arches of which one was distinctly 

 seen by Tarry in bright daylight after the occurrence of a 

 northern light. This phenomenon occurred in England on 

 the 3d of September, 1827, when columns of light were seen 

 shooting up from the luminous arch even by day.* 



It has frequently been asserted that a continuous evolution 

 of light prevails in the sky immediately around the northern 

 magnetic pole. Bravais, who continued to prosecute his ob- 

 servations uninterruptedly for 200 nights, during which he 

 accurately described. 152 aurorae, certainly asserts that nights 

 in which no northern lights are seen are altogether excep- 

 tional ; but he has sometimes found, even when the atmos- 

 phere was perfectly clear, and the view of the horizon was 

 wholly uninterrupted, that not a trace of polar light could 

 be observed throughout the whole night, or else that the 

 magnetic storm did not begin to be apparent until a very late 

 hour. The greatest absolute number of northern lights ap- 

 pears to occur toward the close of the month of September ; 

 and as March, when compared with February and April, 

 seems to exhibit a relatively frequent occurrence of the phe- 

 nomenon, w r e are here led, as in the case of other magnetic 

 phenomena, to conjecture some connection with the period 

 of the equinoxes. To the northern lights which have been 

 seen in Peru, and to the southern lights which have been vis- 

 ible in Scotland, we may add a colored aurora, w T hich was 

 observed for more than two hours continuously by Lafond in 

 the Candide, on the 14th of January, 1831, south of New 

 Holland, in latitude 45°.f 



The accompaniment of sound in the aurora has been as 

 definitely denied by the French physicists and Siljestrom at 



p. 311. An absence of all color seems to be a frequent characteristic 

 of soutbern lights, vol. i., p. 26G; vol. ii., p. 209. Regarding the ab- 

 sence of the northern light in some nights in Lapland, see Bravais, 

 Op. cit., p. 545. 



* Cosmos, vol. i., p. 197. The arch of the aurora seen in bright 

 daylight reminds us, by the intensity of its light, of the nuclei and 

 tails of the comets of 1813 and 1847, which were recognized in the 

 immediate vicinity of the sun in North America, Parma, and London. 

 Op. cit., vol. i., p. 85 ; vol. iii., p. 543. 



t Comptes rendus de VAcad. des Sciences, t. iv., 1837, p. 589. 



