478 Proceedings of the Royal Society of Edinburgh. [Sess. 
XXXI. — On some Nuclei of Cloudy Condensation. 
By John Aitken, F.R.S, 
(MS. received March 21, 1911.) 
Part II. 
There was some difficulty in deciding what the title of this paper should 
be. It ought to have been “ The Abnormal Dust Readings at Kingairloch ” ; 
but as that would convey no suggestion of its contents, it was thought 
better to make the paper a continuation of a previous one under the 
above title, * as the Kingairloch abnormal readings are a particular case of 
the same subject. 
Those who were interested in the Kingairloch observations may 
remember that during the series of tests of atmospheric dust at that place 
the number of particles per c.c. rose occasionally very high. When 
the wind was north-west and the sky clouded, the number of particles was 
generally very low and the air very clear ; but if the north-west wind was 
accompanied by sunshine, then the numbers became very high. In the 
former case, the number was generally about 200 to 300 per c.c. and 
sometimes under 100 ; in the latter, the number increased to thousands 
per c.c. and sometimes was over 10,000 per c.c. The interesting point 
connected with the observations made under these conditions was that 
though the number of particles became very high the air did not lose its 
transparency, but retained much the same appearance as when the number 
was only a few hundreds; if the wind, however, was from any other 
direction, the amount of haze was directly proportional to the number of 
particles present, and with 10,000 per c.c. there would have been produced 
a thick haze. 
The abnormal dust readings at Kingairloch have long remained a 
mystery, though investigations were made at Kingairloch at the time. To 
the north-west of Kingairloch there are some sulphur springs, and the 
baneful influence of sulphur compounds in forming nuclei of cloudy con- 
densation being known, these were suspected ; but on investigation the 
number of particles was found to be the same to the windward as to the 
lee of the springs, which therefore secured a verdict of “Not guilty.” 
* Trans. Roy. Soc. Edin ., vol. xxxix. part i., No. 3. 
