584 



APPENDIX. 



[No. III. 



therefore could not have been more than two miles from the earth, supposing 

 that the elevation of the clouds was 2 J miles. The wind was W., and the 

 temperature of the air 36°. Another circumstance, which twice came under 

 my observation, is too remarkable to be omitted. The Aurora was very 

 brilliant near the zenith, the sky perfectly clear, and the wind moderate, when 

 a discharge took place of small flakes of snow, which continued during several 

 minutes. In both instances, showers of snow had fallen about half an hour 





before ; but at the precise periods of these phenomena, no clouds were visible 

 10° above the horizon. To account for them on any known principles, we 

 must wholly abandon Euler's theory of the zodaical light, and Dr. Halley's 

 circulation of magnetic effluvia. 



On the 27th of April, at 1 Oh. 30m. p. m. , a single column of Aurora rose 

 in the north, and traversed the zenith towards the south ; another column 

 appearing, N.E.b. E., and taking a parallel direction. The frost was slightly 

 agitated, and the beams momentarily visible. It passed to the western 

 horizon in ten minutes, and was followed by the other, which became brighter 

 as it approached the zenith. I am now convinced they were borne away by 

 the wind, because the columns preserved exactly their distance from each 

 other during their evolution ; and some detached wreaths, projected from them, 

 retained the same relative situations of all their parts ; which never happens 

 when the Aurora is carried through the air by its own direct motion. The 

 wind was E.b.N., a strong gale, and the temperature of the air 9°. 



It must be admitted that the influence of the wind upon the Aurora, was 

 never suspected until the 27th of April. However there are several parti- 

 culars connected with the subject, which may have prevented such an influence 

 from manifesting itself on former occasions. 1st. When the coruscations 

 were rapid and brilliant, they forced themselves against the wind, or in the 

 contrary direction, without any perceptible difference of speed ; from which 

 circumstance, I was led to suppose that they were not in any degree affected 

 by the wind, and did not afterwards pay sufficient attention to discover my 

 error. 2nd. The prevalent winds were from the' eastward and westward j 

 and the arches usually extending from N.W. to S.E. ; the influence of the 

 wind might have been mistaken for their lateral motion. 3d. The northerly 

 winds, acting from the same quarter as the direct motion, were confounded with 

 it. Lastly, the southerly winds, which were not common, always filled the 



