30 Mr Potter on the Aurora Borcalis. 



for trigonometrical computation to those who have observed it 

 at some distance from Manchester, on the same magnetic me- 

 ridian. The place at which I observed it is about 1§ miles to 

 the north of Manchester. 



These two arches were very regular and symmetrical, and 

 to the sight evidently very nearly at right angles to the mag- 

 netic meridian ; but between them there occurred a profusion 

 of irregular bands of light, taking different fantastic forms. 

 Often they appeared like loops, turning again on themselves ; 

 at other times they appeared of a waved form, like a ribbon 

 thrown down at random. These bands were generally from 

 4° to 5° broad. They appeared to proceed from an immense 

 mass of nebulous misty light in the north-east, and, when they 

 had extended along the northern horizon, they appeared to 

 light up at their eastern end, and dissipate in streamers and 

 glowing masses, the lighting up proceeding onwards towards 

 the west. When dissipated, other fresh bands of different 

 forms proceeded in the same manner from the eastern maga- 

 zine, if I may so call it, and were dissipated in like manner in 

 their turn. A succession of these phenomena occurred during 

 two hours. At 9 o'clock the aurora was dying away very 

 quickly- About 7 o'clock the western end of the higher arch 

 became of a fine bright ruby red, which continued for some 

 time. Many of the streamers near that end also were of the 

 same tint, and some were red on their western edge, and shad- 

 ing into yellowish green on the eastern. Though the two 

 arches, between which the other phenomena appeared, were 

 symmetrical and at right angles to the magnetic meridian, yet 

 these irregular bands seemed as if less under the same influ- 

 ence ; for, though the whole might pass in the direction of the 

 regular arches, yet parts of them were seen extending in direc- 

 tions at all angles to the meridian. 



The arch which was visible on the evening of the 12th De- 

 cember last was observed by John Blackwall, Esq. of Crump- 

 sail Hall, about two miles north of Manchester ; and I am 

 indebted to him for the following particulars : — " On the even- 

 ing of the 12th December 1830, at 8 h 15 / p. m. a well-defined 

 arch of an Aurora Borealis suddenly succeeded to a splendid 

 display of streamers, which were lighted up from east to west, 



