small motor flame barely more than enough to overbalance the minimized
friction. This is not a supposed or theoretically inferred fact, like
the facts of ventilation sometimes alleged by theorists. On the
contrary, the theory I have offered is merely an attempt to explain
facts that I have witnessed and that anyone can verify with the
anemometer. But the _theory_ by no means covers the art and mystery of
ventilation; for ventilation is truly an _art_ as well as a mystery.
The art lies in a consummate experience of the sizes, proportions, and
forms of flues, their inlets, expansions, and exits, with many other
incidental adaptations necessary, in order to insure under _all_
circumstances the regular exhaustion of any specific volume of air
required, per minute. And this art has by one man been achieved. It
would be a double injustice if I should neglect from any motive to
inform my audience to whom I am indebted for what I know about
ventilation practically, and even for the knowledge that there is any
such fact as a practicable ventilation of houses; one who is no
theorist, but who has felt his way experimentally with his own hands,
for a lifetime, to a practical mastery of the art to which I have
attempted to fit a theory; every one present who is well informed on
this subject must have anticipated already in mind the name of Henry
A. Gouge.

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THE RECENT ERUPTION OF ETNA.