APPENDIX. 59«5 



No. VII. 



ON THE AURORA BOREALIS. 



The observations on this phenomenon were made, 

 without interruption, during six months in the years 

 1833-34, and five months in the years 1834-35 ; but, as 

 their entire insertion would occupy too much space 

 here, I have selected chiefly the instances possessing the 

 greatest interest from the effect produced by them on 

 the needle, and from the brilliancy and eccentric motions 

 of the coruscations. That the needle was constantly 

 affected by the appearance of the aurora, seems evident 

 from the facts thus stated ; and, on one occasion, indeed, 

 this effect exceeded eight degrees. I abstain, how- 

 ever, from drawing any inferences on this subject ; and 

 merely note down carefully, and with as much precision 

 as possible, the whole of the phenomena. 



Brilliant and active coruscations of the aurora bore- 

 alis, when seen through a hazy atmosphere, and ex- 

 hibiting the prismatic colours, almost invariably affected 

 the needle. On the contrary, a very bright aurora, 

 though attended by motion, and even tinged with a 

 dullish red or yellow, in a clear blue sky, seldom pro- 

 duced any sensible change, beyond, at the most, a tremu- 

 lous motion. 



A dense haze or fog, in conjunction with an active 

 aurora, seemed uniformly favourable to the disturbance 

 of the needle ; and a low temperature was favourable to 

 brilliant and active coruscations. On no occasion, 



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