1888 - 89 .] Mr John Aitken on Dust Particles. 
163 
the air here with the new apparatus, hut it is unnecessary to refer 
in detail to the result of these tests, because the air here is so con- 
taminated by artificial causes, that the numbers, though indicating 
the condition of the air in this neighbourhood, are yet of little 
general interest. I have, however, entered in the table the least and 
the greatest numbers observed here. 
A few tests were made of the air in Edinburgh, and the results 
are entered in the table. Those tests were made at the rooms of 
the Royal Society on the Mound. The pipe by which the air was 
taken in to the apparatus was carried to the outer air, through one 
of the windows, on the west side of the building facing Princes 
Street Gardens. The wind at the time was blowing towards the 
west side of the building. The result of these tests, as might be 
expected, show that the air in Edinburgh has a considerably greater 
number of particles in it than the air of this district. The first 
tests were made on 2nd February, and the last on the 5th. The 
numbers obtained on these two days are likely to be small for 
Edinburgh, because the air was clear and cold, with a strongish west 
wind, and heavy snow showers on the 2nd. On the 4th there was 
less' wind, the air was not so clear, and the numbers observed rose 
considerably above what it was on the other days. 
The apparatus was then removed to Glasgow, and tests made of 
the air there. The situation selected for these observations was in 
Both well Street, which is situated near the Central Station. There 
is a large open space in front of the selected position, and the air in 
this street will be a fair average for Glasgow. The first of the tests 
was made on the 8th of February. This was a remarkably stormy 
day. A strong north-west wind was blowing all day, with heavy snow 
showers. The lowest number obtained on that day was 170,000 per 
c.c. It is probable, owing to the high wind, low temperature, and dry 
air, that the air on this day was as free from dust as it is ever likely 
to be. Tests were again made on the 12 th. The day was frosty, 
with westerly wind, sky clear, and air dry. The number counted 
on the 12th was double that obtained on the 8th. On the 16th of 
the month the air was again tested, and found to have even a larger 
number of particles in it than on the 12th. A much stronger wind 
was blowing on the 16th than on the 12th, and yet the numbers 
were highest on the windy day. This might possibly be due to 
