ON THE CARBONIC ACID, ORGANIC MATTER, ETC., IN AIR, 
89 
First determination. 
Second determination. 
Carbonic acid. 
Organic matter. 
Carbonic acid. 
Organic matter. 
In the sewer by the Clock Tower end . . 
7-3 
12-9 
5-2 
11-8 
Ditto, midway between the Clock and 
Victoria Towers. 
8-2 
13-0 
7-0 
9-5 
Ditto, by the Victoria Tower. 
8-5 
9-4 
8-5 
9-4 
The first determinations were made between the hours of 5 p.m. and 7.30 p.m., and 
the second between 10.30 p.m. and 12 midnight. 
5. Effect of Physical Exercise .—As is well known, physical exercise causes a marked 
increase in the amount of carbonic acid exhaled in the breath.A similar effect 
appears to be likewise produced in the quantity of organic matter. We were led to 
this conclusion from the results obtained in the case of a mechanically ventilated 
“ half-time school,” attached to one of the mills in Dundee. The children in this mill 
are divided into two lots, one of which works the first part of the day, and attends 
school the second part, the second lot alternating with the first. On two different 
days we made an examination of the school just before the second school began, the 
room having been first well ventilated for twenty minutes and the carbonic acid and 
organic matter determined. The children were then admitted direct from their work 
in the mill, and the carbonic acid and organic matter again determined at the end of 
thirty minutes, and again at the end of an hour. The results were as follows :— 
First day. 
Second day.f 
Carbonic acid. 
Organic matter. 
Carbonic acid. 
Organic matter. 
Girls' School .—Beginning of hour .... 
3-0 
3-8 
5-0 
3-9 
Middle ,, .... 
9-6 
10-7 
12-3 
6-2 
End ,, .... 
7 T 
6-4 
11-4 
39 
Boys' School .—Beginning of hour .... 
4-0 
5-1 
39 
2-9 
Middle ,, .... 
11-5 
63 
17-1 
4-5 
End ,, .... 
11-2 
7-3 
15-1 
2-9 
6. Cleanliness has little or no apparent influence on the quantity of organic matter 
in air. (See Table, p. 96.) 
* Cf. Parkes’ ' Hygiene,’ p. 148, where Pettenkofer’s statement is quoted to the effect that in hard 
work a man evolves twice as much carbonic acid as in gentle exertion, and three times as much as 
during repose. 
t This was the day of the great snow-storm last winter, when the quantity of organic matter in the 
outside air was much below the average. 
MDOCCLXXXVII.—B. 
N 
