543 
1909—10.] Halley’s Comet and the Earth’s Atmosphere. 
I shall now make a few remarks on some of the figures shown in Table 
No. VII. The E.N.E. winds in that table are more transparent than those of 
the previous years, when the wet-bulb depression was high ; while all other 
easterly winds are less transparent than before. From the 11th to the 
13th July the air was densely hazed, and during this period we were 
situated near the centre of an anticyclone. Afterwards the centre of the 
anticyclone moved away towards Iceland, and we were till the 19th 
situated between an anticyclone and a cyclone, so that during this time 
we were out of the anticy clonic air, and it was then that all the E.N.E. 
observations giving high transparencies were obtained. Further, the 
weather charts show that the general circulation was not E.N.E. on 
these days, but only slightly east of north. This northerly wind when 
it arrives at Falkirk is turned into a more easterly wind by striking the 
southern slopes of the Forth valley, which gives it an increase in its easterly 
component. These observations in E.N.E. winds ought therefore to have 
had their place among the more northerly winds, and in that position would 
show decreased and not increased transparency. 
A word of caution as to any conclusions we may draw from these dust 
and haze observations. It must be remembered that it is about fifteen years 
since the early observations with the dust-counter and on haze were made, 
so that we are comparing the state of the air now with what it was fifteen 
years ago ; and it may be contended that the increase in haze is due 
to the increased consumption of coal. It is very doubtful if the better 
combustion now more general in our furnaces will have done anything to 
balance the effect of the increased consumption, because perfect combustion 
gives rise to many nuclei, while the smoky products soon fall out of the 
air. The increased consumption of coal does not, however, seem to explain 
the condition of the air, because the increase, so far as I have been able 
to ascertain, only amounts to one-fourth during the last fifteen years. It 
is probable, however, that the consumption of coal on the Continent has 
increased to a greater extent than in this country. In addition to their 
own increased output our coal export has been nearly doubled during the 
last fifteen years ; and as our east winds come to us laden with Continental 
impurities, making them always thickly hazed, the increased Continental 
consumption may have some effect. It may also be as well to remember 
that during this year there have been exceptionally extensive forest fires 
in America, and the products from these may have been carried to the upper 
parts of our atmosphere. 
It will be noticed that the abnormally high numbers of dust-particles 
were observed at Morar only when an anticyclone was over the place of 
