80 
PROF. T. CARNELLEY, MR. J. S. HALDANE, AND DR. A. M. ANDERSON 
perceptible draught. When a draught is perceptible it is a warm, and not a cold 
draught, as is the case with ventilation by an open window. 
Mechanical ventilation does not merely reduce the number of micro-organisms 
during the time it is in action, but has, as will be shown below (p. 97), a marked 
effect after it has been stopped and replaced by natural ventilation, this effect 
extending over a period of many days at least. 
Further, mechanical ventilation, as shown by Professors Brazier and Niven, 
of Aberdeen University (see below), keeps the composition of the ah more or less 
constant at different points in a room, whereas with natural ventilation it is liable to 
be much more impure at one part than another. 
We have not included in the above Table the Dundee High School nor the only 
private school we have examined, as in these two cases the cubic space per person was 
about three times as great as in the other schools. The results for these two schools 
were as follows. It will be seen that practically they confirm the conclusions drawn 
from the results in other schools, though the effects of mechanical ventilation are not 
nearly so marked. The reasons for this will appear subsequently (page 98). 
Private school. 
(Girls.) 
Naturally ventilated. 
Dundee High School. 
(Boys and girls.) 
Mechanically ventilated. 
No. of 
No. of 
rooms 
examined. 
Lowest. 
Highest. 
Average. 
Average. 
Lowest. 
Highest. 
rooms 
examined. 
Number present . . . 
3 
6 
11 
9 
36 
13 
64 
6 
Space per person . . . 
3 
320 
528 
457 
538 
320 
1102 
6 
Temperature (° Fahr.) 
3 
56 
57 
57 
57 
51'5 
605 
6 
Carbonic acid .... 
3 
107 
13-3 
11-9 
130 
8'5 
16'4 
6 
Organic matter .... 
3 
62 
11-8 
8-9 
3-9* 
17 
5-6 
6 
Total micro-organisms 
3 
4 
15 
93 
3-6 
1 
11 
7 
Bacteria. 
3 
4 
15 
9-0 
2'9 
1 
10 
7 
Moulds. 
3 
0 
1 
0-3 
07 
0 
3 
7 
Last year Professors Brazier and Niven made a report to the Aberdeen School 
Board on the ventilation of schools in that town. From this report it appears that 
they examined (the carbonic acid only being determined) four different schools venti¬ 
lated in the ordinary manner, and two schools ventilated mechanically by fans. From 
their detailed results we have calculated that the average temperature and carbonic 
acid in excess of the outside air were as follows :— 
*A determination of the organic matter in the outside air was not made when the High School was 
examined; but, as the outside organic matter on the day we visited the private school amounted to 
only R6, the private school must have been considerably in excess of the High School, even allowing 
nothing for the outside air when the latter school was examined. 
