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XXVII. yin Attempt to explain the P hfEnomenon known by the 

 Name cf the Aurora Borealis. By Mr. William Dobbie. 



To Mr. Tilloch. 

 rp Glasgow. Sept. 23, 1820. 



SiRj — J. HE following Essay was written in December 1S16, 

 as an attempt to explain the aurora borealis in connexion with a 

 beautiful pheenonienon seen at Glasgow and most parts of the 

 country on the evening of the 24th September in the above year, 

 and also on the 11th September 1S14. I had for several years 

 before the above periods entertained an opinion as to the cause 

 of the aurora borealis, entirely different from that generally held. 

 The phccnomenon alliuied to was an illumined arch similar to 

 the rainbow,, only colourless, and formed in a clear serene sky. 

 This arch I may say demonstn'ted itself to have the same origin 

 as the common aurora borealis; for towards the conclusion it fell 

 to pieces, and assumed the usual appearance oi streamers. This 

 last circumstance fully confirmed me in my opinion as to the cause 

 of those phfenomena,and I wrote at that time the annexed paper, 

 but never published it. 



I trust the j)revailing hypothesis on this question is fully dis- 

 proved. The one which I offer will be found, I hope, to con- 

 tain hints at least, and data that may lead to a demonstration of 

 its truth by some abler observer. An Essay on some properties 

 of Light in your Number for March last, contains opinions on this 

 subject somevvhaL bordering on mine, the perusal of which in- 

 duced me to send the present Essay for insertion in the Philoso- 

 phical Magazine, should you judge it worthy of a place, I hope 

 the way in which I have disposed of the alleged noise produced 

 by streamers, taken notice of bv the author of the above-men- 

 tioned Essay, will be so convincing that no attempt to account 

 for it is necessary. I have frequently seen these pha^nomena, but 

 never heard the supposed sound, and indeed think that 1 have 

 proved the impossibility of its existence even according to their 

 own hypothesis who believe it. But, far from reflecting on the 

 veracity of respectable persons, who assert that they have heard 

 such noise, I am satisfied that it is an illusion produced partly 

 by tradition, and partly by one sense being affected by another, 

 as more fully explained in the Essay. 



This sympathy of the senses has, I presume, been experienced by 

 many in peculiar circumstances : for instance, in a large building, 

 when full of people, if any sudden and unaccountable noise pro- 

 duce uproar and confusion, in the first state of alarm the eye is 

 apt to be deceived, and an apprehension induced that the timber 

 is bending, supports moving out of their place, and all ready to 



fall: 



