ON THE CARBONIC ACID, ORGANIC MATTER, ETC., IN AIR. 
109 
Remedies. 
It is not within the scope of this paper to discuss at length the methods which 
should be employed for maintaining a reasonably pure atmosphere in schools and in 
dwellings ; but the following suggestions, as the result of experience, may not be 
without some value. 
(1.) As our results show, the state of the air in the Board schools in Dundee is 
extremely bad, and urgently needs improvement. Doubtless the schools in other 
towns are in a similar condition. The symptoms ascribed to overpressure, which has 
been complained of so extensively of late, are probably largely due to the defective 
ventilation of the schools. Defective ventilation weakens and depresses the energies 
so that a child certainly cannot gain the full advantage of its education under a bad 
system of ventilation. It therefore behoves School Boards to pay much more atten¬ 
tion than hitherto to the ventilation of them schools. 
A sufficiently pure air in schools appears to be attainable only by mechanical venti¬ 
lation. It is true, the necessary conditions of purity may also be got by the use of 
open-window ventilation ; but then, in winter at least, the ill-effects of draughts are 
probably greater than those due to insufficient ventilation. 
Of the systems of mechanical ventilation, it is better to blow air into the room, and 
allow it to find its own way out (preferably up special shafts), than to ventilate by 
extraction. Draughts are more easily avoided by the former method. But the great 
objection to the suction method is that a partial vacuum tends to be produced, which 
would greatly accelerate the entry of sewer-gas into the room from any defective 
drains, whereas the “ blow-in ” method has the positive advantage of producing the 
opposite effect. By blowing warm air into a room a much more uniform and higher 
temperature may be attained during winter; and this method is also independent of 
the state of the weather. All parts of the room are more thoroughly heated and 
ventilated than under the natural system. The air should be blown in under a low 
velocity through sufficiently large upright shafts, in order to avoid draughts. 
(2.) In regard to houses, mechanical ventilation is, of course, out of the question, 
but very satisfactory results may be obtained in the case of a large block of buildings 
let out on flats in single- or double-roomed houses, as is largely the case in Scotch 
towns, by having a large open-air space or landing on each flat, and provided with 
open wire-grated windows without glass, so that a good current of fresh air may be 
maintained along the passages and staircases, whereby a pure, instead of an already 
vitiated, air enters and supplies the various rooms. 
This was shown in a very marked manner in a large block of such one-roomed 
houses in Dundee. This block was eight stories high, covered an area of 555 square 
yards, and contained 136 separate one-roomed and four two-roomed dwelling-houses, 
Owing to bad trade, only the four lower flats are now occupied, but a few years ago 
all the houses were tenanted, and then had a population of about 700, or about three 
