ON THE CARBONIC ACID, ORGANIC MATTER, ETC., IN AIR. 
81 
Ratio. 
Temperature. 
(° Falir.) 
Carbonic acid. 
Temperature. 
Carbonic acid. 
Mechanically ventilated. . 
16 
11-0 
Or 
1-0 
1-0 
Naturally ventilated . . . 
14'6 
17-0 
0-9 
1-6 
It will be seen that, though the average excess of carbonic acid found by them was 
somewhat higher than what we have found from the examination of a much larger 
number of schools, yet the ratio is practically the same (1 to 1'6 instead of l to 17). 
Like us, they found the excess of temperature over outside air greater in the mechani¬ 
cally than in the naturally ventilated schools, though the difference is not so marked 
in their observations as in ours. They conclude that mechanically ventilated schools 
“ compare very favourably with those on the other system.” We, however, would 
speak much more strongly than this in favour of mechanical ventilation, since it not 
only considerably reduces the carbonic acid, but effects a very much greater reduction 
of those impurities which are undoubtedly far more injurious to health than the usual 
excess of carbonic acid. It does this also without producing the very objectionable 
fall in temperature necessarily associated with effective natural ventilation. We 
entirely agree with Professors Brazier and Niven in believing that the system of 
ventilating by open windows is, for winter, at least, very objectionable. The severe 
draughts thus produced are possibly a worse evil than defective ventilation. 
It is true that mechanical ventilation is apparently more costly; but it remains to 
be proved that it really is so. As our results show, the cubic space per child would 
not require to be nearly so great, in order to maintain a given standard of purity, on 
the mechanical as on the “ natural ” system. Hence the cost of building would be 
less. The cost of heating would also be reduced, on account of the smaller space to 
be heated. The reduction in space could most advantageously be made in the height 
of the rooms. 
The chief difficulty in connexion with mechanical ventilation is to maintain a 
proper distribution of the air, and consequently of the heat, in several rooms within 
the same building. With proper care, however, there is no reason why this should 
not be accomplished. 
The all-important argument for mechanical ventilation is that it maintains a certain 
standard of purity, and, unless some simpler method which will maintain a similar 
standard can be devised, its adoption in crowded schools seems to be very much 
required. 
When we come to consider that the children who attend average Board schools for 
six hours a day are during that time subjected to an atmosphere containing on an 
average nearly 19 volumes of carbonic acid per 10,000, and a very large propor¬ 
tion of organic matter, and no less than 155 micro-organisms at least per litre, w r e 
MDCCCLXXXVII.—B. M 
