s, thirty-two thousand four
hundred cubic inches of air impart their entire vitality to support
animal life _the first minute_, and, mingling with the atmosphere of the
room, proportionably deteriorate the whole mass; that the air of crowded
school-rooms thus soon becomes entirely unfit for respiration, and that,
as the necessary result, the health of both teacher and scholars is
endangered; that the scholars gradually lose both the desire and the
ability to study, and become more inclined to be disorderly, while the
teacher becomes continually more unfit either to teach or govern. Hence
the necessity of frequent and thorough ventilation.

The ordinary facilities for ventilating school-rooms consist in opening
a door and raising the lower sash of the windows. The only ventilation
which has been practiced in the great majority of schools has been
entirely accidental, and has consisted in opening and closing the outer
door as the scholars enter and pass out of the school-house, before
school, during the recesses, and at noon. Ventilation, as such, I may
safely say, has not, until within a few years, been practiced in one
school in fifty; nor is it at the present time in many parts of the
country. It is true, the door has at times been set open a few minutes,
and the windows have been occasionally raised, but the object has been
either to let the smoke pass out of the room, or to cool it when it has
become too warm, not to ventilate it.

Ventilation by opening a door or raising the windows is imperfect, and
frequently injurious. A more effectual and safer method of ventilation
consists in lowering the upper sash of the window. In very cold or
stormy weather, a ventilator in the ceiling may be opened, so as to
allow the vitiated air to escape into the attic, in which case there
should be a free communication between the attic and the outer air by
means of a lattice in the gable, or otherwise. A ventilator may also be
constructed in connection with the chimney, by carrying up a partition
in the middle, one half of the chimney being used for a smoke flue, and
the other half for a ventilator.

But it is often asked, Why is it not just as well to raise the lower
sash of the windows as to lower the upper one? In reply I would say,
first, lowering the upper sash is _a more effectual method of
ventilation_. In a room which is warmed and occupied in cold weather,
the warmer and more vitiated portions of the air rise to the upper