Yorkville enquirer. [volume] (Yorkville, S.C.) 1855-2006, 1897-09-08
aMistellanepns 8eading.
EARTHQUAKES.

sometimes interfere with the comfort
of man and occasionally imperil his
existence-food, drought, winds, tides,
frost heat, thunder and lightning-not
one is to be classed with earthquakes
in the degree of apprehension and
terror which they create during their
actual happening.
Fortunately in most parts OF the
world they occur only at long inter-
walls, and probably only very small
number of the people of the United
States have any notion, based on actu-
al experience, of the nature of an
earthquake.
Curiously enough, those who have
resided in "earthquake countries" and
have felt many shocks, are the most
easily frightened by any disturbance
which resembles, and which may be,
an earthquake. One does not "become
accustomed" to earthquakes for the
reason that, while experience nas
taught US that flood, wind, tide, frost
and heat reach maximum of intensi-
ty and duration, beyond which it is
extremely improbable that they will
ever go, it is impossible to know how
an earthquake will end. Beside, as
yet we are without hint as to any
principles upon which an earthquake
may be predicted.
The motion of the surface of the
earth during an earthquake is general
ly somewhat like that of the surface OF
water disturbed by waves. 1t is not
exactly the same, for the principal
movement of any particular drop or
mass of water in wave motion is up
and down, while that of particular
part of the earth during the passage of
earthquake waves is generally all up
and down motion combined with to-
Promotion in q horizontal plane,
and often the latter will largely pre-
dominate.
An earthquake is sometimes accom-
panied by a dull, roaring sound. The
sound may even precede the sensible
disturbance of the surface. as happen
ed many times in the series OF shocks
which followed the great Charleston
earthquake of 1886.
Earthquakes of even moderate inten-
sity often cause men and women to
suffer from a kind of sickness closely
resembling seasickness.
Like other wave motions an earth
quake is produced by some more or
less violent disturbance in the medium
in which it occurs. This is often a
sudden displacement of a part of it,
as portion of water is displaced when
stone is dropped into quiet pond.
In the earth this disturbance or dis
placement generally occurs at con-
siderable depth below the surface, Of
ten many miles. From this point
waves are transmitted in all direc-
tions, coming to the surface at various
angles, according to the distance from
the point vertically above the centre
of disturbance where the motion is
mostly vertical.
Not much is yet known of the causes
to which the original disturbance may
be attributed, but ingenious instru-
ments have been devised within the
past few years by means Of which an
earthquake is made to leave written
record of its very complex motion, to
tell its own story, in fact, and in this
way much is being learned.
"Although there is no great Seismic
activity" in that part of the earth di-
rectly below the United States, yet an
earthquake may occur at any point ;
but we may be tolerable sure that over
most of the country the disturbances
will be of great intensity.
Some idea of the energy involved is
suggested by the results of study of
the destructive japanese earthquake
of 1891. Considering only that part
of the wave which reached the surface,
the crate of working" during one
minute could not have been less than
five hundred thousand million horse
power Youths Companion.