344 Mr Blackader*'s^6ro?^w^o/'an Aurora Borealis 



The following remarks seem necessary to illustrate this re- 

 markable aurora. 



1 . The streams, or spears of light, were uniformly projected 

 downwards, from an immense elevation ; in this particular bear- 

 ing a resemblance to the usual appearance of the larger shoot- 

 ing-stars, or those nearest the observer. The colour of their 

 light is also similar, and they coincide in being most brilliant at 

 the expanded or lower portion ; where, in each, the rapidity of 

 projection, emulating the glance of thought, seems to be arrested 

 in the act of dissolution, when they gradually disappear. The 

 shooting-stars are the more evanescent, and frequently more 

 brilliant. The shape of the diminishing swells, exhibited at the 

 period of dissipation, indicate that this meteor is of the spheroi- 

 dal form. On some occasions, also, their exit takes place beyond 

 the verge of the horizon, or is concealed by the vapours inter- 

 posed in that direction. The expiring blaze is by these means 

 concealed ; but the course of the meteor appears much more ex- 

 tended, in proportion to the distance of that course from the 

 zenith. 



2. The difference in the colour and intensity of the light of 

 this aurora, from right to left, bore a resemblance to that of 

 the moon, when near the horizon, compared with her light at a 

 greater elevation. The cause may be found in the incipient 

 change, on the lower atmosphere, which had commenced on 

 tlie south or south-west, with the wind from that quarter. 



3. A luminous undulation seemed to traverse, by fits, diffe- 

 rent portions of the lengthened congeries of luminous forms, 

 ■which, less or more developed, appear to constitute the grand 

 arch. For some time this undulation was uniformly from right 

 to left. Towards the close it occurred repeatedly in the con- 

 trary direction. A very short observation was sufficient to sa- 

 tisfy me that no undulation takes place. It is merely the effect 

 of a strong light behind- the line under view, and concealed 

 thereby, — passing to and fro, to right or left, it successively im- 

 parts an increased luminosity, of different intensities, which, be- 

 ing transmitted in succession, through the various and varying 

 forms of the front line, produces an appearance of undulation. 

 The posterior light may easily be detected, passing the less per- 

 fect portions of the front line ; for here the expression of an un- 



