Notice of the late Aurora Borealis. 97 



Whether the phenomena of the aurora borealis are attrib- 

 utable to electricity, or to the reflection, and refraction of 

 the sun's rays, appears to be at this day, as questionable as 

 ever. A writer in the London Philosophical Magazine and 

 Journal, objects to the doctrine that they are electrical phe- 

 nomena, and asks if they be such — 



" Why is their appearance confined to particular times of the 

 year and of the night 1 



" Why are they always seen in a particular quarter of the 

 heavens ? 



" Why do they in general assume the particular form and posi- 

 tion observable, rather than any other ? 



" Why are they under all their various appearances different 

 in color from the electric fluid in other cases ? 



" And, lastly, why is the motion of the electric fluid so dissim- 

 ilar to that of streamers, the former being determined by known 

 laws ; whereas the latter move to and fro laterally, without even 

 a conjecture as to the cause of such motion ?" 



Considering these questions as unanswerable, the writer 

 accounts for the phenomena as follows. 



"It is generally at or near the time of the equinoxes that those 

 lights make their appearance in these latitudes, at which times 

 the sun's rays would be tangents to the poles of the earth, were 

 they not disturbed by the refractive power of the atmosphere. 

 By the refraction, it is obvious that the rays will extend to a cer- 

 tain point beyond the pole, on the side opposite to the sun, when 

 they must of course fall on the immense accumulation of ice with- 

 in the polar circle, which will be reflected with great brilliancy 

 towards the darkened hemisphere, undergoing in their course 

 another refraction, which bends them still more southward ; and 

 as the atmosphere possesses also the power of reflecting light, 

 those rays will finally fall back on the earth, and will at a certain 

 angle and within certain limits be visible to its inhabitants." 



Upon this ground, the author thinks there will be no diffi- 

 culty in accounting for the phenomena, and for their annual 

 and diurnal times of appearance. He accounts for the mo- 

 tion of the streamers, upon the supposition, that the bodies 

 of ice, by which they are probably reflected are in motion, 

 and says, 



" If a mass of ice, by rolling or falling, change its position sixty 

 degrees, it is evident the streamer reflected bv it will in the same 

 Vol. XIV.— No. 1. 13 



