y filling up the two inch space along the front,
as shown in the drawing, with coarse perforated metal. This will also
prevent cinders from getting under it. It will be found that for the
greater part of the year the chimney ventilator and the supply to the
fire will materially prevent "stuffiness," and keep those disagreeable
draughts under control, even although the room be lighted with a 3 light
chandelier burning a large quantity of gas.

[Illustration]

With improvements in gas burners, we may expect to light rooms perfectly
with a less expenditure of gas than we now do. But we cannot light a
room without in some measure creating heat; and I think I have shown
that we want this heat at the ceiling line for the greater part of the
year.

In summer we do not use gas for many hours; but, on the other hand, it
is more difficult, with an outside temperature at 65 deg. to 70 deg. Fahr., to
keep the air in proper movement in small rooms. There are also times in
the fall of the year, and also in spring, when the nights are unusually
warm; and, with a few friends in our rooms, the lighting becomes a "hot"
question, not to say a "burning" one. On these occasions we have to
resort to exceptional ventilation, which for ordinary every-day life
would be too much. It is then, and on summer nights, that the system of
ventilation by diffusion is most useful. To explain it, when two volumes
of air of different temperatures or specific gravities find themselves
on opposite sides of a screen or other medium, of muslin, cloth, or some
more or less porous substance, they diffuse themselves through this
medium with varying rapidity, until they become of equal density or
temperature. Therefore, if we fill the upper part of a window (which can
be opened, downward) with a strained piece of fine muslin or washed
common calico, the air in the room, if hotter than the external air,
will, when the window is more or less opened, pass out readily into the
cooler air, and the cooler air will pass in through the pores of the
medium. The hotter air passing out faster than the cooler air will come
in, no draught will be experienced; and the window may be opened very
widely without any discomfort from it.

It is, of course, quite impossible, in the limits of a paper, to do more
than indicate a means of ventilation which will be effective under most
circumstances of lighting with those gas burners and fittings usually
employed, and which will lend