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ceiling, so that the fresh air may diffuse itself into the
upper part of the chamber, and not drop down upon the
heads of the inmates. If the inlet have an air-way too
large to meet the suck of the chimney, the in-draught will
enter the room so sluggishly as to pour directly down upon
the inmates. The size of the inlet, therefore, must be
such as to adequately provide for the suck of the chimney,
but yet to make the air enter with such momentum as
will carry it across the top of the room and make the
current break up against the opposite wall.
2. The staircase face of the inlet should be guarded by a
silk flap-valve. This works without noise. Being very
light, it rises instantly under the suction of the fire and
allows air to pass freely from the staircase into the room.
But when no fire is alight the silk flap-valve falls down and
closes the inlet. This prevents reflux into the staircase,
which would be attended by a down-draught through the
chimney into the room.
3. As to the general-inlet in the basement, this is
intended to supply the staircase with a volume of air equal
to that which is driven up the working chimneys by all the
fires which may be alight. In winter, therefore, when many
fires are alight, this inlet must be more widely open than
it need be in the summer, when there are no fires in the
living-rooms, and when also open windows and doors are
available. If the basement general-inlet be negligently or
perversely closed, the fires are not able to draw freely,
and smoking is easily produced in chimneys which have
fires alight. So far as the lighted fireplaces then do
draw, they get their air through crevices—as previously
described. Part of this supply comes from the staircase
of the house, and this cannot be drawn from the staircase
unless an adequate counter-current enters the staircase. If
the basement general-inlet be closed, the cold bedroom
chimneys have to serve as downcast shafts and they fill the
staircase and bedrooms with smuts, which ruin the carpets
and furniture. The question, therefore, is not whether
air is to be admitted to supply the lighted fireplaces—the