ON THE CARBONIC ACID, ORGANIC MATTER, ETC., IN AIR. 
69 
volumes, outside which cases very seldom occur. He states that carbonic acid is 
lowest in winter and on the seashore. Levy (‘ Annuaire de Montsouris/ 1882) gives 
the mean carbonic acid at the observatory of Montsouris (suburbs of Paris) as 
3 - 0 volumes. The mean carbonic acid in air appears to be distinctly lower than the 
quantity (4 volumes) maintained by the older authorities. 
Mtquel finds that the number of micro-organisms is also much greater in the centre 
of a town than in the suburbs. This is doubtless due to the stir in the town raising 
dust, &c. (see below). Our own observation that the number of organisms is greater 
during the day in a town is what might be expected for the same reasons. In this 
connexion it will be of interest to give the results of four observations made on two 
different nights in one of the central courts of the Houses of Parliament in April and 
May of the present year. 
Time. 
Carbonic 
Acid. 
Organic 
matter. 
Total 
micro¬ 
organisms. 
Bacteria. 
Moulds. 
April 19-20th j P ' M - ’ 
^ t 1.0 A.M. . 
May 18-19th { j™, ™ ; 
4-1 
4-i 
4-4 
31 
2-5 
too small 
9-2 
4-0 
18-0 
3-0 
9'2 
3-6 
14-0 
1-5 
0 
0-4 
4-0 
1-5 
At the time of the first observation in each pair the streets were very busy. 
These results, so far as they go, are in perfect accord with the conclusions deduced 
from the results in Dundee. 
The Air of Dwelling-Houses, 
Mode and Time of taking Samples of Air .—The samples were taken during the 
night, between 12.30 a.m. and 4.30 a.m. This appeared to be the most favourable 
time for avoiding disturbing conditions, and at the same time obtaining fair specimens 
of the air breathed during the night. The one-roomed houses were mostly those of 
the very poor. Sometimes as many as six, or even eight, persons occupied the one bed. 
In other cases there was no bed at all. The occupants of the two-roomed houses were 
as a rule much better off, belonging mostly to the artisan class. 
Mr. Kinnear, the head of the Sanitary Department of Dundee, was good enough 
to place at our disposal a horse and covered van, by which means we were enabled to 
make the analyses in the street outside the houses selected for examination. Two of 
the inspectors belonging to the same department assisted us in our work in the case 
of the poorer class of houses. Those houses were visited without warning of any 
kind to the inhabitants, so as to avoid the risk of having the rooms specially venti¬ 
lated in preparation for our visit. In every case but one we were most civilly 
