is quite conceivable, and not incredible, that such
a current may be gradually established and thenceforward
permanently maintained by a 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.
* * * *
*
THE RECENT ERUPTION OF ETNA.
On the morning of the 20th of March, a long series
of earthquakes spread alarm throughout all the cities
and numerous villages that are scattered over the
sides of Mt. Etna. The shocks followed each
other at intervals of a few minutes; dull subterranean
rumblings were heard; and a catastrophe was seen to
be impending. Toward evening the ground cracked
at the lower part of the south side of the mountain,
at the limit of the cultivated zone, and at four kilometers
to the north of the village of Nicolosi. There
formed on the earth a large number of very wide fissures,
through which escaped great volumes of steam and gases
which enveloped the mountain in a thick haze; and toward
night, a very bright red light, which, seen from Catania,
seemed to come out in great waves from the foot of
the mountain, announced the coming of the lava.
[Illustration: ERUPTION OF MOUNT ETNA, MARCH
22, 1883.]
Eleven eruptions occurred during the night, and shot
into the air fiery scoriae which, in a short time,
formed three hillocks from forty to fifty meters in
height. The jet of scoriae was accompanied with
strong detonations, and the oscillations of the ground
were of such violence that the bells in the villages
of Nicolosi and Pedara rang of themselves. The
general consternation was the greater in that the