hich the warm air will escape. But
replenishing this inevitable loss would be a small matter, if the
breath of life were a needless luxury. Unless, however, we are willing
to suck poison into our veins with every breath we draw, slow but
sure,--poison expired from our lungs and emanating from our bodies,
poisonous gases liberated by the combustion of fuel, poison dust and
decay from the waste of inorganic material,--we must have a
never-ceasing supply of fresh air around us everywhere and always. Now
this incoming fluid, cold as ice, eats fuel like a hungry giant, yet
we must receive it with open arms, and, as soon as fairly warmed, send
it off through the ventilating flue, bearing whatever noxious
elements may chance to be afloat, and, of course, much of the warmth
we love and buy so dearly. We have then to supply these three sources
of loss. Obviously for economy the two former must be prevented to the
utmost, the latter rigidly controlled.

Thus far, except the old fogies who don't believe in ventilation, we
can all travel together harmoniously. Now our way divides, the doctors
begin to differ, and the patients begin to die.

The first fork is at the two modes of warming, direct and indirect.
The former includes stoves of all sorts,--sheet or cast iron,
porcelain, soapstone, brick or pottery, box or cylinder, for wood or
coal, air-tight, Franklin, "cannon," or base-burner, parlor cook or
kitchen cook, charcoal basin, warming-pan or foot-stove,--anything in
which you can build a fire. It includes open grates and fireplaces,
ancient or modern, large or small; it includes steam-pipes, hot-water
pipes, and stove-pipes; and last, but not least, steam-radiators, than
which it has never entered into the heart of man to conceive anything
more surprising and unaccountable,--flat, pin-cushiony things, big as
a bedquilt, dangerous-looking hedgehoggy affairs, some huge and
bungling, others frail and leaky, but radiators still. In brief, the
heating apparatus, whatever it may be, stands in the room to be
warmed.

By the indirect mode it is enclosed in a chamber more or less remote,
commonly called a furnace, and made of brick, sheet-iron, or wood
lined with tin. Into this chamber cold air is admitted from some
source, and escapes by its own levity, usually through tin pipes, to
the rooms where the heat is needed. Sometimes it is driven out by
mechanical means.

The advocates of the latter indirect mode claim for it many
adv