158 COSMOS. 



ranged in the form of polar bands correspond, according to 

 the above developed views, in respect to position, with the 

 luminous columns or bundles of rays which ascend in the 

 true Aurora towards the zenith from the arch, which is 

 generally inclined in an east and west direction ; and they 

 cannot, therefore, be confounded with those arches of which 

 one was distinctly seen by Parry in bright day-light after 

 the occurrence of a northern light. This phenomenon oc- 

 curred in England on the 3rd of September, 1827, when 

 columns of light were seen shooting up from the luminous 

 arch even by day. 14 



It has frequently been asserted that a continuous evolu- 

 tion of light prevails in the sky immediately around the 

 northern magnetic pole. Bravais, who continued to prose- 

 cute his observations uninterruptedly for 200 nights, during 

 which he accurately described 152 Aurorse, certainly asserts 

 that nights, in which no northern lights are seen, are alto- 

 gether exceptional, but he has sometimes found even when the 

 atmosphere 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 

 appears to occur towards 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, we are here led, as in the case of other magnetic 

 phenomena, to conjecture some connection with the period 



I'arc des Aurores bore"ales, pp. 534 537), describes with his accustomed 

 exactitude the turnings or rotations of the true arch of the Aurora 

 borealis, pp. 27, 92, 122, 487. Sir James Ross has likewise observed in 

 the southern hemisphere similar progressive alterations of the arch of 

 the Aurora (a progression in the southern lights from W.N.W. E.S.E. 

 to N.N.E. S.S.W.) Voyage in the Southern and Antarctic Regions, vol. i, 

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

 of southern lights, vol. i, p. 266, vol. ii, p. 209. Regarding the absence 

 of the northern light in some nights in Lapland, see Bravais, Op. cit. 

 p. 545. 



14 Cosmos, vol. i, p. 191. The arch of the Aurora seen in bright day- 

 light reminds us by the intensity of its light of the miclei and tails of 

 the comets of 1843 and 1847, which were recognised in the immediate 

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

 vol. i, p. 85, vol. iii. p. 543. 



