544 
Proceedings of the Royal Society of Edinburgh. [Sess. 
observation, and that the same thing happened at Appin. Under cyclonic 
conditions the numbers were much as previously observed, but with the 
approach of an anticyclone the figures became high even in air coming 
from what are usually pure directions. The observations on haze at 
Falkirk also point to the same conclusion. All the abnormally densely - 
hazed days occurred while the circulation was anticyclonic ; and the nearer 
the centre of the anticyclone was to the place, the denser was the haze. 
These facts all point one way, namely, that there was something in the 
descending air of the anticyclones which increased the number of dust- 
particles in the pure areas and greatly increased the haze in the polluted 
areas. Now, one must not rush to the conclusion that both these results 
indicate one thing, namely, that they are due to the dust contents of the 
anticyclonic air ; because the increased dust and haze in the pure areas, if 
added to the air of our polluted districts, would have but little or no effect 
on its transparency. If, then, the increased haze is due to the comet, it 
must have had, in addition to its dust, some hazing quality, with which 
we are not acquainted, which, when added to dusty air, increases its hazing 
effect. 
If the change in our atmosphere which these observations demonstrate 
be due to the tail of the comet, then one would have expected that the dust, 
or emanation, or whatever , it may be supposed to be, would have had some 
effect on the upper part of our atmosphere immediately after the passage ; 
but, so far as I am aware, no such effects have been recorded. So far as 
my observations go, there has been no increase in the colour of the sunsets. 
Both when at Morar and Appin I was most favourably situated for observ- 
ing sunsets, but never saw any good colouring. Before the passage of the 
comet the sunsets at Morar were finer-coloured than I have seen since. I 
took some colour-photographs of sunsets before the passage, but have not 
seen a sunset since worth exposing a plate on. So far as my observations 
go, instead of the colours being finer they seem to be quite the reverse. At 
Appin cloudy evenings gave no fine colouring, and on some evenings the 
sun set in perfectly cloudless skies, but the north-west horizon never showed 
more than a poor and rather dirty yellow, and not so much colour as was 
visible in the south-east sky. None of the evenings showed as much colour 
as was seen under similar conditions at Morar before the passage, when 
the records were taken in colour-photographs. 
Thunderstorms. 
The great number of thunderstorms of unusual violence which have 
occurred in this country and all over the Continent, and probably else- 
