128 Mr. W. Sturgeon's Account of an Aurora Dorcalis 



These two arches of light were frequently, after this time, very 

 badly defined, ever varying in breadth, and softening gradually 

 into shade, particularly at their convex edges, by the lambent 

 streamers which gently played into the partially illuminated 

 expanse above. These soft gliding streams seemed in conti- 

 nual play between the bright arches, flashing from the convex 

 edge of the lower or innermost, and sometimes blending the 

 two curves into one confused light, but never to that extent 

 as to obliterate the distinction of the two luminous arche-, 

 which the eye could always trace by the superior refulgence 

 of their light. Between nine and ten o'clock the altitude of 

 the superior arch advanced from 20 to about 24, but never 

 ascended higher than that point. The inner, or inferior, arch 

 advanced at the same time, and apparently in the same pro- 

 portion, so that the same distance (about 10) between the 

 two curves of strongest light, was nearly, perhaps exactly , pre- 

 served during the whole time. The extremities of these arches 

 never completely reached the horizon, but were gradually lost 

 in a dark gloom, resembling an exceedingly dense fog, al- 

 though the atmosphere in every other part was perfectly clear. 

 This appearance was particularly remarked on the eastern 

 limbs, which were lost at various altitudes. The western 

 limbs of the bright curves could not be so distinctly traced at 

 the place where these observations were made, on account of 

 their mixing with the reflected light in the atmosphere, of the 

 burning gas in London, which, at Woolwich, is always seen, 

 in the night, as a bright cloud hovering over the metropolis. 



About nine o'clock I called on Mr. Barlow, to inform him 

 of the aurora. Mr. B., however, had seen it all the evening. 

 I remarked before I left him, that the centre of the aurora in 

 the horizon was considerably to the west of the north, and 

 near to the magnetic meridian, a circumstance which he had 

 already observed. I immediately returned home, and having 

 a very delicately suspended magnetic needle, I placed it in a 

 suitable situation for observation, and so far neutralized the 

 magnetism of the earth, as to leave no more power acting on 

 the needle than was barely sufficient to arrange it in the mag- 

 netic meridian. I observed this needle, at intervals of two or 

 three minutes, during the remainder of the display of the au- 

 rora, but never detected the slightest change in its direction, 

 nor was its repose in the least disturbed by any influence 

 which I could ascribe to that phenomenon.* 



At half-past nine the aurora increased in splendour, and 

 shot its beautiful broad streamers upwards, as radii, from the 



* See our " Intelligence," in the present Number. 



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