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APPENDIX. 
VIII. 
AURORA BOREALIS. 
We had frequent opportunities of observing the Aurora Borealis in the autumns of 
1826 and of 1827. From the 25th of August until the 9th October, about the time of the 
departure of the Blossom from the northern regions in both years, this beautiful meteor was 
visible on every night that was clear, or when the clouds were thin and elevated *. It is 
remarkable that, in both years, its first appearance was on the 25th August. The season 
of 1826 w'as distinguished by an almost uninterrupted succession of fine weather and easterly 
winds, and that of the following year by continued boisterous weather and winds from the 
westward. In the former year, the weather being fine, the Aurora was more frequently 
seen than in the latter; but in 1827 the displays were brighter, and the light more fre- 
quently passed to the southward of the zenith. It never appeared in wet weather. 
In 1826, when, as before mentioned, the weather was settled, the Aurora generally 
began in the W.N.W. and passed over to the N.E., until a certain period, after which 
it as regularly commenced in the N.E. and passed to the N.W. ; whilst in 1827 the ap- 
pearance of the meteor was as uncertain as the season was boisterous and changeable. The 
period when this change in the course of the light took place coincided very nearly with 
that of the equinox ; and as the Aurora Borealis has been supposed to be affected by that 
occurrence, we imagined that the change might be in some way owing thereto, but the 
irregularity of the meteor in this respect in 1827 gave a contradiction to this hypothesis. 
It was, however, uniform in making its appearance always in the northern hemisphere, and 
generally in the form of elliptical arches from 3® to 7® of altitude, nearly parallel with the 
magnetic equator. These arches were formed by short perpendicular rays passing from one 
quarter to the other with a lateral motion, or by their being met by similar rays from the 
opposite direction. The arches, when formed, in general remained nearly stationary, and gave 
out coruscations, which streamed toward the zenith. When at rest the light was colourless, 
but when any movement took place it exhibited prismatic colours, which increased in strength 
as the motion became rapid. The coruscations seldom reached our zenith, and more rarely 
passed to the southward of it, but when that occurred the display was always brilliant : on 
one occasion only they extended to the southern horizon. 
We remarked, that when any material change was about to occur one extremity of the 
arch became illuminated, and that this light passed along the belt with a tremulous hesi- 
tating movement toward the opposite end, exhibiting the colours of the rainbow. An idea 
may be formed of this appearance from the examination of the rays of some moluscous 
animals in motion, such as the nereis, but more particularly the heroes. Captain Parry has 
In 1826 it was visible on twenty-one nights, in 1827 only eleven. 
