open
fireplaces are the rule, it is not unusual to find that more than
ninety per cent. of the heat produced behind the domestic hearth goes
up the chimney.

Sentiment has had a great deal to do with retarding progress in the
direction of improved house-heating appliances. For countless ages
"the hearth" has been, so to speak, the domestic altar, around which
some of the most sacred associations of mankind have gathered, and
popular sentiment has declared that it is not for the iconoclastic
inventor or architect to improve it out of existence, or even to
interfere seriously with either its shape or the position in the
living room from which it sheds its genial warmth and cheerfulness
around the family circle. A recognition of this ineradicable popular
feeling was involved in the adoption of the grate, filled with glowing
balls of asbestos composition, by the makers of gas-heating apparatus.
The imitation of the coal-filled grate is in some cases almost
perfect; and yet it is in this close approximation to the real article
that some lovers of the domestic fuel-fire find their chief objection,
just as the tricks of anthropoid animals--so strongly reminiscent of
human beings and yet distinct--have the effect of repelling some
people far more than the ways of creatures utterly unlike man in form
and feature.

Taking count of the domestic attachment to a real fuel-filled
fireplace or grate as one of the principal factors in the problem of
domestic heating, it is plain that one way of obviating the waste of
heat which is at present incurred, without doing violence to that
sentiment, is by making better use of the chimney. The hot-air pipes
and coils which are already so largely used for indoor heating offer
in themselves a hint in this direction. Long pipes or coils inserted
in the course taken by the heated air in ascending a chimney become
warm, and it is possible, by taking such a pipe from one part of the
room up the passage and back again, to cause, by means of a small
rotating fan or other ventilating apparatus, the whole of the air in
the chamber to circulate up the chimney and back again every few
minutes, gathering warmth as it goes. In this way, and by exposing as
much heating surface to the warm air in the chimney as possible, the
warmth derived by an ordinary room from a fuel fire can be more than
doubled.

At the same time the risk of spreading "smuts" over the room can be
entirely avoided first by keeping