They fail us utterly when most needed, in warm and murky weather, when
the barometer is low, and the thin atmosphere drops, down its damp and
dirty contents, burying us to the chimney tops in a pestilent
congregation of vapors.

Nevertheless, so far as I can discover, these holes and flues, at best
a little fire at the bottom of the latter, are the sole and
all-sufficient expedients of science and architecture for ventilation
to this _day_, in spite of their total failure in experience. I can
find nothing in standard treatises or examples from philosophers or
architects, beyond a theoretical calculation on so much expansion of
air from so many units of heat, and hence so much ascensional force
_inferred_ in the ventilating flue--a result which never comes to
pass, yet none the less continues to be cheerfully relied on.
Unfortunately for the facts, they contradict the philosophy, and are
only to be ignored with silent contempt. A French Academician's report
on the ventilation of a large public building, lately reprinted by the
Smithsonian Institution, states with absolute assurance and exactness
the cubic feet of air changed per minute, with the precise volume and
velocity of its ascension, by burning a peck of coal at the bottom of
the trunk flue. No mention is made of the anemometer or any other
gauge of the result asserted, and we are left to the suspicion that it
is merely a matter of theoretical inference, as usual; for every one
who has had any acquaintance with practical tests in these matters
knows that no such movement of air ever takes place under such
conditions, unless by exceptional favor of the weather.

I have seen a tall steam boiler chimney induce through a four inch
pipe a suction strong enough to exhaust the air from a large room as
fast as perfect ventilation would require. But this, it is well known,