called, are more or less the same in each case--carbonic acid and steam.

These facts justify the expression I just made use of--which may have
seemed to some of you fantastical--that the fire and the candles in the
crowded room were breathing the same breath as you were. It is but too
true. An average fire in the grate requires, to keep it burning, as much
oxygen as several human beings do; each candle or lamp must have its
share of oxygen likewise, and that a very considerable one; and an
average gas-burner--pray attend to this, you who live in rooms lighted
with gas--consumes as much oxygen as several candles. All alike are
making carbonic acid. The carbonic acid of the fire happily escapes up
the chimney in the smoke: but the carbonic acid from the human beings and
the candles remains to poison the room, unless it be ventilated.

Now, I think you may understand one of the simplest, and yet most
terrible, cases of want of ventilation--death by the fumes of charcoal. A
human being shut up in a room, of which every crack is closed, with a pan
of burning charcoal, falls asleep, never to wake again. His inward fire
is competing with the fire of the charcoal for the oxygen of the room;
both are making carbonic acid out of it: but the charcoal, being the
stronger of the two, gets all the oxygen to itself, and leaves the human
being nothing to inhale but the carbonic acid which it has made. The
human being, being the weaker, dies first: but the charcoal dies also.
When it has exhausted all the oxygen of the room, it cools, goes out, and
is found in the morning half-consumed beside its victim. If you put a
giant or an elephant, I should conceive, into that room, instead of a
human being, the case would be reversed for a time: the elephant would
put out the burning charcoal by the carbonic acid from his mighty lungs;
and then, when he had exhausted all the air in the room, die likewise of
his own carbonic acid.