not in use, quite open; for each admits as much air as a hole in the
wall would do, or a pane deficient in a window. Perhaps the best mode of
admitting air to feed the fires is through tubes, leading directly from
the outer air to the fire-place, and provided with what are called
throttle-valves, for the regulation of the quantity; or the fresh air
admitted by tubes may be made first to spread in the room, having been
warmed during its passage inwards, by coming near the fire.--In a
perfectly close apartment, ventilation must be expressly provided for by
an opening near the ceiling, to allow the impure air rising from the
respiration of the company to pass away at once; but with an open fire,
the purpose is effected by the frequent change of the whole air of the
room which that construction occasions.

With a view to have the most perfect security against cold blasts and
fluctuation of temperature in rooms intended for invalids, and still to
retain the so much valued appearance of the open fire, a glazed frame or
window may be placed at the entrance of the chimney, so as completely to
prevent the passage of air from the room to the fire. The close room
will then be warmed by the fire through the glass, as a green-house is
warmed by the rays of the sun. It is true, that the heat of combustion
does not pass through glass so readily as the heat of the sun; but the
difference is not important. The glass of such a window must, of course,
be divided into small panes, and supported by a metallic frame work; and
there must be a flap or door in the frame work, for the purpose of
admitting the fuel and stirring the fire. Air must be supplied to the
fire as described above, by a tube leading directly from the external
atmosphere. The ventilation of the room may be effected by an opening
into the chimney near the ceiling; and the temperature may be regulated
with great precision by a valve placed in this opening, and made to obey
the dilatation and contraction of a piece of wire affixed to it, the