VOL. XXIX.] PHILOSOPHICAL TRANSACTIONS. 217 



segment of a ring or zone of the sphere, intercepted between two paralld lesser 

 circles, cut off likewise by the horizon ; or, if you please, the segment of a 

 very broad iris, but of one uniform colour, viz. a flame-colour inclining to 

 yellow, its centre being about 40 degrees below the horizon. And above this 

 there were seen some rudiments of a much larger segment, with an interval of 

 dark sky between ; but this was so exceedingly faint and uncertain, that I could 

 make no proper estimate of it. 



I was very desirous to have seen how this phenomenon would end, and 

 attended it till near three in the morning, and the rising of the moon; but for 

 above two hours together it had no manner of change in its appearance, nor 

 diminution nor increase of light: only sometimes for very short intervals, as if 

 new fuel had been cast on a fire, the light seemed to undulate and sparkle, not 

 unlike the rising of vapourous smoke out of a great blaze when agitated. But 

 one thing I assured myself of by this attendance and watching, viz. that this 

 iris-like figure by no means owed its origin to the sun's beams; for that about 

 three in the morning, the sun being in the middle between the north and east, 

 our aurora had not followed him, but ended in that very point where he then 

 was; whereas in the true north, which the sun had long passed, the light 

 remained unchanged, and in its full lustre. 



Hitherto I have endeavoured by words to represent what I saw, but being 

 sensible how insufficient such a verbal description of a thing so extraordinary 

 and unknown may be to most readers, I have thought fit to annex a figure, 

 exhibiting that particular appearance of the two laminae, which I saw at London 

 between the hours of 10 and 1 1 ; more especially, because I do not find, among 

 the many accounts I have seen, any one that has taken notice of it. In this 

 figure, fig. ] , pi. 5, AB is the imder lamina, somewhat broader and brighter 

 than the upper cd: it had near its under edge the lucida lyras, and below its 

 northern extremity, on the left hand, cauda cygni: and as well above and below 

 these as in the intermediate space between them, and indeed all round about 

 that part of the heavens, the sky was so unusually dark and black, as if all that 

 exotic light that had showed itself before, had been then collected into those 

 two streaks. Only at q, between the west and northwest, and no where else, 

 out of a brightness adjoining to the horizon, there arose conical beams, as m, l, 

 N, after the same manner as at first. 



While we stood looking on, the streak cd at its northern end bent down- 

 ward, and joined with the under ab at e, and included the space dceab, which 

 still kept open at the other end towards the east. And in the mean time, out 

 of the very clear sky, some luminous spots, situated and figured as in the 

 scheme at g, g, g, g, presented themselves to the eye, in colour much like the 



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