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
advantages. It is apparently clean. There are no ashes to be taken
up, no hearths to sweep, no andirons to polish, no stoves to black.
One fire will warm the entire house if well arranged, and, for a trump
card, there may be a supply of fresh air straight from the north pole,
but agreeably warmed, constantly entering the room.

The objections are less numerous but more weighty. The liability to
imperfect construction and careless management often makes a furnace,
especially a cast-iron one, a savor of death unto death rather than of
health and comfort; also, when we are warmed by air thrown into a room
at a high temperature, and dry at that, a greater degree of heat is
necessary for comfort than if our bodies and clothing absorb heat from
a radiating surface. The furnace, in short, compels us to breathe an
atmosphere highly rarefied. We have the most careful and competent
authority for believing this to be gravely injurious.