CHAPTER III. 



AURORA BOREALIS. 



"Tins is a luminous meteor usually appearing in tlie northern 

 part of the sky, and presenting a light somewhat resembling 

 the dawn or break of day." The aurora exhibits such a variety 

 of forms at different times, that no general description can give 

 any definite idea of its appearance: this, however, may be 

 easily attained by observation of the meteor itsel It appears 

 to be a horizontal cloud extending towards the east and west, 

 and rising a few, degrees above the horizon. The lower part 

 of the cloud is often darkish,, and the upper part lu.minous and 

 whitish: from this part, streams or columns of light shoot 

 upwards with an unsteady, wave-like motion, reaching some- 

 times to the zenith, and at others only a few degrees above the- 

 horizon. 



The "Northern Lights" usually appear two or three hours,, 

 or soon after sunset, and continue a few hours, and occasionally 

 the whole night : they, also sometimes appear for several sue- - 

 cessive nights, but are rarely seen after midnight or in the 

 morning. [Brande.] They often succeed a change of weather 

 from heat and rain to cold and clear. They are sometimes 

 tinged with .green ; or orange, but more commonly with various 

 shades of red.; The aurora is sometimes seen in the southern \ 

 hemisphere. The mean height of the luminous sheet has been 

 variously estimated a^ from : 100 to 400 miles. No satisfactory. 



