observed at Edinburgh \Qth January 1827. 345 



dulation disappears, and the play of the remote streams of light 

 is brought directly to the eye. 



The resemblance of an immense vibrating curtain was readily 

 suggested by the form of the front line of the arch, when most 

 irregular, and particularly 'vhen the posterior lights, in frequent 

 motion, combined their efforts with the various flitting motions 

 of the front. But I do not apprehend any lateral motion of 

 these luminous rays. I conceive that what appears to be mo- 

 tion, is merely an effect of the vertical projection of circular 

 screens in lateral succession ; the deception being aided by the 

 great rapidity, and the distance and indistinctness of the opera- 

 tions. It seems quite possible that the front-swells of the prin- 

 cipal or chiefly stationary arch, concealed similar curtained ex- 

 tensions on the same plane. As a counterpart, the second arch 

 becoming broader and brighter than the first, covered a great 

 portion of it longitudinally, and concealed the star. Thereafter 

 the succession of advanced lights, already described, reappeared 

 in front of the western half. 



4. As the aurora borealis and the shooting star stand connected 

 with changeable weather, or, at least, with extensive transposi- 

 tion of masses, or strata of the atmosphere ; and, as the aurora 

 has, by continued observation, been connected with a change of 

 current, in the region of the lower clouds, often extending to 

 the earth, whereby the south-west or equatorial currents dis- 

 place those from the north-east, without disturbance of the strata 

 occupying more serene altitudes ; it would seem very possible 

 that the different states of electricity in the contiguous strata, 

 might dispose to equalization, in the form of the aurora, or, 

 under other circumstances of transposition of strata, in that of 

 the shooting-star. 



5. After the aurora of the 16th had disappeared, a thin re- 

 ticulated cloudy tissue could be discerned, of seemingly great 

 elevation. But the actual height of the higher tiers of clouds, 

 viewed by moon-light, is not easily estimated. The splendour 

 and peculiar light of this aurora, opposed to a brilliant moon, 

 afforded no point of comparison whereby to estimate its eleva- 

 tion, although it appeared most provokingly near. For the na- 

 ture of its light seemed quite distinct from that of any of the 

 heavenly bodies ; and what it wanted of intensity, seemed to 



