412 Proceedings of the Royal Society 
the most part cloudless, is suffused with thin pale vapours 
especially in longitudinal streaks.” 
I beg here to be allowed to make a short digression. The 
phenomena of the aurora borealis in this country have often been 
minutely described on the occurrence of unusually fine displays of 
it. But no one, so far as I am aware, has studied carefully its 
prognostications. Thoroughly inquired into, however, these may 
prove practically valuable, as the following illustration will serve 
to show. Every one knows that when the aurora first begins to 
exhibit in the autumn it is regarded as a sign of broken weather 
following. But at that period of the year it supplies a prognostic 
of far greater precision and importance. I have repeatedly men- 
tioned to my friends the observation I have invariably made, that 
the first great aurora after autumn is well advanced, and following 
a long tract of fine weather, is a sign of a great storm of rain and 
wind on the forenoon of the second day afterwards. I must have 
noticed this fact very early, because I applied it on the occasion of 
the first meeting of the British Association in Edinburgh on 8th 
September 1834. There had been a long tract of very fine weather, 
for a fortnight and more, when on Saturday evening, the 6th of the 
month, there appeared the widest, brightest, and most flashing 
aurora I have ever seen. Next day the weather continuing remark- 
ably fine, Professor Sedgewick described, at breakfast at Dr Alison’s, 
in glowing language, the magnificent exhibition which the philo- 
sophers of Edinburgh had provided for their southern visitors. 
Presenting then to him the dark side of the picture, I told him 
that the Association meeting was to be inaugurated with a great 
storm. He was surprised at this, and appealed to the continuing 
cloudless sunny sky against me ; but I told him the particulars of 
the prognostication, and that the storm would not begin till the 
middle of the following day. Next morning the weather was 
equally splendid. But soon after eleven the eastern sky began to 
be overcast, an ominous low north-easterly black cloud rose by 
degrees ; at twelve, as the offices of the Association opened, rain 
began to fall from that direction, and in a short time there com- 
menced the most incessant and heaviest fall of north-east rain I 
ever witnessed, lasting without intermission till one o’clock on 
Wednesday the 10th, when the fine weather was again restored to 
