1889 - 90 .] 
Mr J. Aitken on Dust Particles. 
205 
value, too few observations being obtained. After descending from 
the tower some tests were made of the lower air. These tests, owing 
to the kindness of M. Mascart, were made in the garden of the 
meteorological office in the Rue de PIJnivershA The situation is 
not far from the tower, and the air at this place would be much 
the same as at the base of the tower. The number at the low level 
was very great when the tests were made. The number, however, 
varies greatly at low levels near the sources of pollution, owing to 
local circumstances, and the number varies greatly from time to time. 
On this occasion the number varied from 210,000 to 134,000 per 
c.c. In the same situation in March the number was much lower, 
being 92,000, the difference being probably due to atmospheric 
conditions. In March the air was much dryer. 
London. 
The only observations of interest made in London were taken on 
the 3rd of June. The day was bright and dry, with a fresh westerly 
wind. Observations were made at the window of an hotel in Victoria 
Street, and also in a garden on the bank of the Thames a little 
below Battersea Bridge. To this latter situation the air came direct 
from Battersea Park uncontaminated by immediate local pollution. 
It will be seen from the table that the numbers for Battersea Park 
varied from 48,000 to 116,000, the number varying a good deal with 
the velocity of the wind. It would be interesting to know what the 
number is at this situation when the air is damp and heavy and 
but little wind blowing. As no such day occurred during my visit, 
there was no opportunity of testing this point. 
Kingairloch . 
The next observations entered in the table were taken at 
Kingairloch in July. Kingairloch is situated in Argyleshire, in the 
wilds of the West Highlands, amidst the mountains on the north- 
west side of Loch Linnhe, nearly opposite Port Appin. At this 
situation the air is very free from local pollution, there being only a 
very few houses for many square miles. The air at this situation 
was generally very pure, but the amount of dust was occasionally 
found to vary considerably at short intervals. This was particu- 
larly the case when the wind blew across the valley in which the 
