Staunton spectator. [volume] (Staunton, Va.) 1849-1896, 1851-07-02
AGRICULTURAL. SCIENTIFIC.
aoT.Tros OF THE EARTH VISIBLE.

The pendulum within the well in the In
t.r;or of Bunker Hill Monument, arranged
under the direction of Prof. Horstord, for
the purpose of exhibiting Foucaulfs curious
and interesting experiment, for rendering
visible the rotation of the Earth, has been
completed. and will be opened to the public
ON Monday. We were kindly permitted to
witness its operation yesterday afternoon in
anticipation.
The pendulum consists of heavy iron
cannon ball, suspended in brass frame
from light wire ZIG feet in length, OF the
size known as Piano No. 90. The pendu-
hum is swung over circle placed at 'he
bottom of the well u feet IN diameter
which is divided into degrees, numbering
from to $50. The apparatus is set II. mo-
ton by drawing the pendulum aside care
fully. fixing it by string which is then
burnt of, thus leaving it free to vibrate to
and fro, across the centre of the floor. A
single vibration of the pendulum occupies
about seven seconds. After few vibra-
tons, it is distinctly visible to the eye that
it continually returns to point in the cir
Gle upon the floor, little to the left of that
where it last was, so that in about SIX MIN
utes at the end of about fifty vibrations, 1t
has advanced one degree to the left, and in
about an hour, ten degrees. The effect is
still more clearly shown by sight which
is so arranged, that the eye can at any CIV
en- instant, BIO brought to range with the
plane in which the pendulum moves at that
instant. By keeping the sight stationary,
and then again looking through it, the
change of position of the pendulum is clear
ly apparent.
The wire of the pendulum admits of such
torsion as to allow the pendulum to follow
its own direction, uninauenced by any cir
cumstances connected with its support. 1t
is suspended without any escapement, but
will swing for upwards of five hours con-
tinuously without stopping.
Some persons have difficulty in under
standing the cause of the phenomenon, on
account of the acknowledged motion of the
point of suspension of the pendulum, which
1t is evident must take place at this lati-
tsle, and at all points of the earth except
the poles. AT the poles, if the pendulum
be suspended directly above the earth at
point which is the line of its axis, this point
will remain immovable, notwithstanding
the rotation of the earth. The centre of
the earth which attracts the pendulum and
causes its motion, is also unmoved by its
rotation. There is no reason, then, why
the pendulum should ever vibrate in any
other plane than that in which it is first
started-its own inertia will prevent its
ever vibrating out of that plane. While
then the pendulum vibrates continuously in
one fixed direction, the earth being rotating
under it, the line over which the pendulum
vibrates will appear to be in continuous mo-
ton and will return to its original place at
the expiration Of "a hours.
The reason then why the earth can be
seen to rotate at Bunker Hill is this: PEN
dulum is started, which continues to swing
In plane which, although not fixed, yet
moves with. motion only partially connect
ed with that of the earth while the earth
is moving under it with a regular continuous
motion.
Prof. Horsford has prepared globe at
4he monument, which, in connection with
the pendulum itself, furnishes an opportuni-
~ for witnessing and comprehending this
curious and instructive experiment, which
should not be neglected.-Boston Daily I'd
Sertiser.