ally displacing the fluid poison that
filled the room, and was about to do the work of death. It seemed as
though I was standing at the mouth of a huge sepulcher, in which the
dead were being restored to life. After a short pause, I proceeded with
a few remarks, chiefly, however, on the subject of respiration and
ventilation. The trustees, who had just tested their accuracy and
bearing upon their comfort and health, resolved immediately to provide
for ventilation according to the suggestions in the article on
school-houses in the last chapter of this work.

Before leaving the house on that occasion, I was informed an evening
meeting had been attended there the preceding week, which they were
obliged to dismiss before the ordinary exercises were concluded,
because, as they said, "We all got sick, and the candles went almost
out." Little did they realize, probably, that the light of life became
just as nearly extinct as did the candles. Had they remained there a
little longer, both would have gone out together, and there would have
been reacted the memorable tragedy of the _Black Hole_ in Calcutta, into
which were thrust a garrison of one hundred and forty-six persons, one
hundred and twenty-three of whom perished miserably in a few hours,
being suffocated by the confined air.

What has been said in the preceding pages on the philosophy of
respiration was first given to the public nearly ten years ago, in a
report of the author's in the State of New York. He has since seen the
same sentiments inculcated by many of our most eminent practical
educators, some of whom had written upon the subject at an earlier date.
Allen and Pepy showed by experiment that air which has been once
breathed contains eight and a half per cent. of carbonic acid, and that
no continuance of the respiration of the same air could make it take up
more than ten per cent. Air, then, when once respired, has taken up more
than _four fifths_ of the amount of this noxious gas that it can be made
to by any number of breathings.

Dr. Clark, in his work on Consumption, remarks as follows: "Were I to
select two circumstances which influence the health, especially during
the growth of the body, more than others, and concerning which the
public, ignorant at present, ought to be well informed, they would be
the proper adaptation of food to difference of age and constitution, and
the constant supply of pure air for respiration." Dr. William A. Alcott,
who has gi