Mr William Sturgeon on Ihe Aurora Borealis. 149 



ward of Arctiirus ; the star being much higher than the auroral arch, 

 but as it was fast descending towards the iiorizon, it passed through 

 the arch, whilst the latter remained stationary, or nearly so. Some 

 fine groups of lambent streamers occasionally flowed upwards from 

 different parts of the glowing bow; and also another feature which 

 the aurora sometimes displays — the gentle blushes of pale soft light, 

 were frequently seen in the dim haze that almost invariably accom- 

 panies tlie aurora borealis. Between seven and eight o'clock, a few 

 strao-o-lino- clouds came floating across the aurora. Such interruptions 

 to tlie observer" s view are exceedingly interesting events, for they 

 never fail to shew that the auroral light is at a greater distance from 

 the place of observation than the clouds themselves, which is one step, 

 at least, gained towards obtaining a true theory of the cauhe of the 

 meteor ; but should nothing farther be ascertained, by the interpo- 

 sition of these clouds, than the locality or region of the atmosphere 

 in which the aurora is situated, it would be the means of setting at 

 rest an inquiry of great interest, concerning the real height of the 

 meteor. 



There are other features occasionally conspicuous in the aurora 

 borealis, which have long been noticed, and rendered as the most 

 astonishing appearance of the whole, I allude to the colours that 

 sometimes adorn the meteor. They have for a long time appeared 

 to me to arise from a decomposition of the true auroral light (white 

 light, or rather that of a soft, pale candle-flame), accomplished by 

 refractions and reflections amongst the abundance of aqueous par- 

 ticles hanging in the regions of air, where the electric fluid is in mo- 

 tion, or between those regions and the eye of the spectator. There 

 can be no doubt of the electric origin of the aurora borealis, since 

 many of its characteristics can be beautifully imitated by the electri- 

 cal apparatus. The violet tint is easily produced by an electrical 

 discharge through highly-attenuated air ; but the green, the blue, 

 the orange, the yellow, and the deep red, cannot be imitated by any 

 form of electrical experiment hitherto known, in which the light is 

 shewn in common air, however much it may be attenuated. But 

 these colours may easily be accounted for, under the supposition of 

 an abundance of aqueous vapour in the regions of an auroral display, 

 a concession by no means unreasonable, when we take into account 

 the season of the year (from about the autumnal to the vernal equi- 

 nox), in which such spectacles are mo.'^t frequent, the hazy appear- 

 ance of the sky at the time, and the occurrence of wet weather that 

 usually follows. 



By looking over my journal for several years past, I find that 

 the grandest displays of the aurora borealis have been closely fol- 

 lowed by wet weather ; and the following extract from the descrip- 

 tion of an aurora which I observed in the vicinity of London, on the 

 evening of 3d September 1839, will probably appear more eminently 

 calculated to develop the true ciiaracter of the spectral colours ac- 



