114 REV. J. FARQUHARSON’S EXPERIMENTS ON THE INFLUENCE 
rently stationary over the higher summits, and present themselves in these 
situations when the rest of the sky is clear. The explanation is quite simple. 
The lower saturated strata of air being carried over the summits, the dimi- 
nished pressure and consequent expansion lower the temperature to the point 
of condensation ; and as the air in its progress again descends, a reverse effect 
occurs, and the vapour is again dissolved. A cloud of this kind appeared to 
rest the whole time of the appearance of the Aurora over the line of the Coreen 
hills, little elevated above them, and appearing to furnish, as it were, the base 
of the bright Aurora in the northern part of the sky. 
It has been stated that a detached cloud rested on the S. W. horizon ; 
and the description of the circumstances attending it has been deferred till 
now. It continued apparently stationary all the time of the observations 
from 20 minutes to 9 till a quarter to 10 ; and I had no difficulty in 
referring it with certainty to the summit of a large hill about six miles 
from this place, having considerably more elevation than the Alford hills, 
and standing several miles apart from any summit of nearly equal height. 
Now over the top of this cloud, which was quite free of the northern Aurora, 
and also of the nebulous Aurora at the S. horizon, there continued the whole 
time a very bright nebulous light. The large hill referred to is not itself 
visible from this place, on account of a high ground about a mile distant. 
I have little doubt also that the nebulous Aurora at the S. horizon, which 
likewise continued the whole time, ought to be referred to a range of hills 
extending E. and W., about seven miles distant, and nearly as high as the 
Coreen hills. A high ground about three quarters of a mile distant conceals 
these hills from view, and would also conceal clouds over them, as high as 
those above the Coreen, on this evening. 
It would thus appear that the pencils or bundles of parallel rays of the 
Aurora, denominated streamers, and whose longitudinal dimensions always 
show themselves parallel to the dipping needle, become indistinct at the 
distance of a few miles, being blended and softened down into a nebulous 
light by the refraction and haze of the atmosphere. 
The wind the whole time was a rather strong gale a point or two S. of W. 
There have been very severe gales from the same quarter for three days past. 
I have this evening again seen several falling stars during the continu- 
