810 Rev. Mr Farquh arson on the Aurora Borealis . 
flection of its peculiar fitful light. It precedes or accompanies 
westerly or south-easterly gales. 
A question arises concerning the height of the aurora borea- 
lis above the surface of the earth. To that question I can give 
only a conjectural answer, arising out of one singular phenome- 
non which I had occasion to observe last winter. 
During the continuance of a pleasant south-westerly gale, of 
mild temperature, the atmosphere, which had been cloudy 
through the day, became quite clear about sunset ; and, after 
dark, a pale aurora borealis appeared in the north, which I was 
observing at short intervals. Its lower or north edge had be- 
come elevated about 20° above the visible horizon at the magne- 
tic meridian, when a solitary cloud appeared under it near that 
point, making its way rapidly from the west. It soon became 
evident that the meteor was affected by tins cloud in a very re- 
markable manner. The lower extremity of the pencils of rays 
of the aurora borealis, appeared in contact with the upper part 
of the cloud, and the light of those pencils of rays directly over 
the cloud became very vivid, in comparison with those which 
the cloud had not yet reached. At the same time, the upper 
edges of the cloud itself became phosphorescent, exhibiting a 
denser and whiter light than could have been occasioned by any 
reflection of the greenish rays above it ; while behind, in the 
space which the cloud had passed through, the aurora borealis 
became quite extinct. These singular appearances accompanied 
the cloud, while it passed from about NNW. to NNE ; when 
the aurora borealis, having apparently passed to the southward 
of the cloud’s path, was no longer affected by it ; and the eastern 
portion of it continued visible for a considerable time ; whereas 
the part which had been influenced by the cloud no more ap- 
peared. 
From this instance, it would seem that the region of the au- 
rora borealis is above, and immediately contiguous to that in 
which the clouds are forming, at the time of its appearance. 
It would seem, also, from the above detail, that this latitude 
is near the extreme limits of the ordinary extension of the me- 
teor towards the south. 
February 3. 1828. 
