Staunton spectator. [volume] (Staunton, Va.) 1849-1896, 1851-05-07
THE ROTATION OF THE EARTH VISIBLE.

THE ROTATION OF THE EARTH vlsIBLE
| The experiment now being exhibited in
Paris. by which the diurnal rotation Of the
earth is rendered palpable to the sense, is
one of the most remarkable of the modern
notifications of theory. Although the DEM
onstration by which the rotation ofthe earth
has been established to be such as to carry
conviction to the minds of all who are ca
pable of comprehending it, to which nothing
can be imaginedto add either force or clear
ness, nevertheless even the natural philoso-
pher himself cannot regard the present ex-
pertinent without feelings Of profound inter
est and satisfaction, and to the great mass,
"a. whom The complicated physical phenom-
ena by which the rotation Of the earth has
been established are incomprehensible. this
experiment is invaluable. AT the centre OF
the dome of the Pantheon fine wire is at
tached, from which sphere ofmetal, four
or FIVE inches in diameter, is suspended so
as to hang near the floor of the building
This apparatus is, put in vibration after the
manner of pendulum. Under, and con-
centrical with H. - placsd oireuiM tabte,
some twenty feet in 35aneter, the circmm-
ference of which is divided INTO degrees,
minutes, &C., and the divisions numbered
Now, it can be shown by the most elenen-
tary principles of mechanics, that, suppo-
sing the earth to have the diurnal motion
upon lts axis which is imputed to it, and
which explains the phenomena Of day and
night, &C., the plane IN which this pendn-
lum vibrates will not be affected by this di-
urnal motion, but will maintain strictly the
same direction during twenty-four hours
In this interval, however, the table over
which the pendulum is suspended viii con-
tinually change its position in virtue OF the
diurnal motion, so as to make complete
revolution round its centre.
Since then, the table thus reyolves, and
the pendulum which vibrates over It does
not revolve, the consequence is that line
traced upon the table by point projecting
from the bottom of the ball will change its
direction relatively to the table, from minute
to minute and from hour to hour, 80 that If
such point were pencil and that paper were
spread upon the table, the course formed by
this pencil during twenty-four hours would
form a system Of lines radiating from, the
centre of the table, and the two lines form
ed after the interval of one hour would al
ways form an angle with each other Of 10
deg, being the twenty-fourth part ofthe cir
cumference. Now this is rendered actually
visible to the crowds which daily flock to
the Pantheon to witness this remarkable ex-
pertinent. The practised eye of a correct
observer especially if aided by proper op-
tical instrun ent, may actually see the mo-
ton which the table has, in common with
the earth, under the pendulum, between two
successive vibrations. 1t is, in fact, appa-
rent that the ball, or rather the point attach
ed to the bottom of the ball, does not return
precisely to the same point Of the circumfe-
renee of the table after two successive VI
brations. Thus is rendered visible the mo-
ton which the table has IN common with
the earth. 1t is true that, correctly speak
ing, the table does not turn round its own
centre but turns round the axis Of the
earth nevertheless, the effect of the motion
relatively to the pendulum suspended over
the centre of the table is precisely the same
as it would be if the table moved once in
twenty-four hours round its own centre, for
although the table be turned, in common
with the surface of the earth, round the
earth's axis, the point of suspension Of the
pendulum is turned also in the same time
round the same axis, being continually main
tanned vertical above the centre of the table.
The plane in which the pendulum vibrates
does not, however, partake of this motion,
and consequently, has the appearance ofre.
volving once in twenty-four hours over the
takle, while, in reality, it is the table which
revolves once in twenty hours under
it.-London Globe, .Apr,l s.