448 EXPERIMENTAL INVESTIGATIONS. 



burner, except that this gives a feeble light at the point, while 

 the aurora tips were whitest and brightest there, the streamers 

 now fading off, and now becoming brighter and tinged with 

 red as they got to 40 or 50 from the horizon ; the tips varied 

 constantly, but preserved the mean distance from the pole or 

 focus of the aurora. The position of this was, as far as I 

 could ascertain without star-maps or instruments for observa- 

 tion, about 15 WNW. of Vega. The convergence of the 

 beams was not in appearance conical, but dome or cupola 

 shaped ; this was, however, in all probability an optical illu- 

 sion. Whether there was really a convergence or whether the 

 beams were parallel, and the convergence an effect of per- 

 spective, can only be decided if some approximate measures 

 of the distance of the streamers be ascertained. It appears to 

 have been at a greater distance from the earth than is usually 

 attributed to aurora borealis, having been seen in different 

 parts of Europe and, I believe, in America. Doubtless the 

 comparison of these observations will give some parallax or 

 approximation to measurement of the distance. I remember 

 about seven or eight years ago seeing an aurora at Chester, 

 where the flashes appeared close to the observer, so that gleams 

 of light continuous with the streamers could be seen between 

 the houses of the town and myself, like the portions of a rain- 

 bow intervening between terrestrial objects and the observer. 

 I tried then to ascertain if there was any reflection or other 

 cause of optical illusion, but could not see it as other than a 

 real effect ; I seemed, so to speak, to be in the aurora. The 

 effect on the 25th was very different, and gave me the idea of 

 great distance. 



The light was sufficient to enable me to tell the time by 

 my watch easily, but not to read newspaper print. 



Between half-past six and seven o'clock it faded away, 

 and at from half-past seven to ten had become an ordinary 

 white aurora, confined to the northern portion of the heavens. 



