VOYAGE TO SPITZBERGEN. 17 



the constant attendants of clear evenings, and prove 

 great reliefs, amidst the gloom of the dark winter 

 night. They commonly appear at twilight, near 

 the horizon, of a dun colour, approaching to yel- 

 low ; sometimes continuing in that state for several 

 hours without any apparent motion, after which 

 they break out into streams of stronger light, 

 spreading into columns, and altering slowly into 

 ten thousand different shapes, varying their colours 

 from all the lines of yellow to the most obscure 

 russet. They often cover the whole hemisphere, 

 and then make the most brilliant appearance. 

 Their motions at these times are amazingly quick ; 

 and they astonish the spectator with the rapid 

 change of their form. They break out in places 

 where none were seen before, skimming briskly 

 along the heavens: are suddenly extinguished, and 

 leave behind an uniform dusky tract. This again 

 is brilliantly illuminated in the same manner, and 

 as suddenly left a dull blank. In certain nights 

 they assume the appearance of vast columns, on 

 one side of the deepest yellow, on the other declin- 

 ing away, till it become undistinguished from the 

 sky. 



They have generally a strong tremulous motion 

 from end to end, which continues till the whole va- 

 nish. According to the state of the atmosphere, 



