542 
Proceedings of the Royal Society of Edinburgh. [Sess. 
limits of visibility for the different winds at Falkirk at the different wet- 
bulb depressions will be found in Table No. V., while the lowest and 
highest readings are given in Table No. VI. 
An examination of Tables No. III. and No. Y. shows that there has been a 
great increase in the haze in certain winds since the early observations, and it 
will be noticed that the greatest increase is in the easterly winds ; it is also 
marked in the south-westerlys, while the north-westerlys are not much 
affected. For comparison there are arranged in Table No. VII. the limits of 
visibility of the first series of observations and those of this year for E.N.E. 
and E. winds. In Tables No. III. and No. Y. there is a considerable number 
of observations for each wet-bulb depression for these directions of wind, and 
the results are thus the more reliable. In the E.N.E. observation, when the 
wet-bulb depression was under 5 degrees, the limit is much less this year 
than before ; but in the observations made when the wet-bulb depression was 
over 5 degrees the limit is greater than in the first series. I shall refer 
to this later. The observations taken in east wind this year show that it 
was about five times more hazed at all wet-bulb depressions, except those 
taken when the depression was very great, when the increase in the haze 
was more than three times that of the first observations. 
Further, an examination of the individual observations shows that the 
lowest limit observed in these winds in the first observations was 3 miles 
in E.N.E. winds and 4 miles in E. winds, while the figures for this year 
show that a limit of 1J miles was observed on five occasions, and that 
limits of 2 and 3 miles were frequent in dry air. 
Turning again to the weather charts, let us see if the circulation in our 
atmosphere throws any light on these observations. When the haze read- 
ings began this year on the 15th June an anticyclone was situated over 
our area, where it remained till the 21st. During these days the limit of 
visibility was always exceptionally low, 1J miles being frequent even in 
dry air. On the 21st a feeble cyclonic circulation came in from the west, 
but was not well developed till the 25th. During the first part of this cir- 
culation the limit rose slightly, but after the 25th, when the circulation was 
well established, the limit extended, and the air remained clear till the 29th 
of June, when the observations closed. 
When the second series of observations began on my return from Appin 
on the 11th July, the circulation was again anticy clonic and the haze dense, 
but not so many readings of 1J miles were noted as during the June anti- 
cyclone. The circulation remained anticyclonic till the 17th, but the centre 
of the anticyclone had receded from our area, and the limit of visibility 
had begun to increase. 
