Yet we build and furnish more wisely than our ancestors. They
ventilated because they couldn't help it, couldn't afford to build as
we do, and could afford to burn an acre of woodland every year.

It is no light task you have set me preliminary to an honorable
discharge. Next to theology and government finance there is no subject
on which the doctors differ and dogmatize as in this matter of warming
and ventilating, most of them preferring that the universe should
suffocate rather than their pet theories and furnaces be found
wanting. (I'm not speaking of the theologians.)

Let me restate a few general principles, simple and obvious, yet so
important that we must not risk forgetting them. Air runs away with
heat fast enough if allowed to move. Confined it is a more effectual
barrier than granite walls and plates of steel. Hence the spaces in
the wall should not extend its whole height unless for local
ventilation. Cut them off surely at each floor, and as much oftener as
you please; also make the floors tight and warm. Deafen with mortar if
you can afford it, and do not allow the open spaces between the
floor-timbers to extend unbroken through the house, or fail to close
them between the rafters when the ceiling of the highest story is
above the plates. If you wish to warm the entire house, it will be
good economy to lath and plaster along the under side of the rafters
quite to the ridgepole. Finally put on your double windows, and you
are ready for winter quarters.

In theory, the house being once warmed, the temperature within should
scarcely change, even if the fire goes out. Practically, the walls
cannot hold this subtile caloric, however scientifically they are