, the desired ends may be
completely attained at little cost.

The great error committed in regard to ventilation has been the want of
an outlet in or near the cieling of rooms, for the air rendered impure in
them by the breathing of inmates and the burning of candles, lamps, gas,
&c. At present the only outlet of English rooms is the fire place or
chimney opening near the floor. But all the impurities above referred to
rise at once towards the cieling, because of the lessened specific
gravity of air when heated, and there they would at once escape by a fit
opening. Where there is no such opening, however, they become diffused
in the upper air of the room, and can escape only slowly by diving under
the chimney-piece as that air is changed. Thus the air of a room above
the level of the fire-place, whenever there are people or lights in the
room, must always be loaded, more or less, with impurity. The purest air
of the room is that near the floor, being the last that entered, and the
coolest, therefore and heaviest specifically; and with this the fire is
fed, while the hotter impure air remains almost stagnant above, around
the heads and mouths of the company. To remove the evil here referred
to, I have shown, that even with an open fire, if the throat of the
chimney be properly narrowed by a register flap, an opening made near the
cieling into the chimney flue, with a valve in it to allow air from the
room to enter the chimney, but allowing no smoke to come out--will serve
very effectually; and that where there is no open fire the ventilation
can, by the means described, be made still more complete.

The great error with respect to warming in rooms for many inmates has
been to have all the heat radiating (none being given off by contact)
from one focus or fire place, persons near to which consequently must
receive too much, and those far from which will receive too little; while
the supply of fresh air enters, cold, at a few openings chiefly, and
pours dangerously on persons sitting near these. In common rooms, with
open fires, the evils described may be lessened considerably by admitting
fresh air through tubes or channels which open either near the fire, or
all along the skirtings so that the fresh air is equally distributed over
the room and mixed with the mass of air previously in it: but to have
what is desirable, the air before distribution must be warmed by some of
the simple means now known, as of warm cha