Burlington free press. [volume] (Burlington, Vt.) 1827-1865, 1851-05-09


The experiment now being exhibiting il
Paris, by which the diurna rotation of the
eattll is rendered paIrabIe to the senses, is one
! OF Tie most remarkable Of The modern verfca.
u9ns OF theory. Although the demonstration
by which the rota lion of the earh has been es.
ta0llshed be such as to c.rry a conviction ,c
the minds of all who arc capable of compre.
hPndlng it, to which nothing can be imagined
to add either force or clearness, nevertheless
even the natural philosopher himself cannot re-
gard the present experiment without feelings OF
profound interest and satisfaction, and to the
great mass, to whom the complicated physical
phenomena by which the rotation of the earth
has been established are incomprehensbe th S
experiment is invaluable.
AT the centre of the dome Of the Pantheon a
fhe wire is attached, from which sphere OF
metal, tour or five inches in diameter, is sus-
pended SO as to hang near the floor Of the build
ing. This apparatus is put in vibration after
the manner OF pendulum. Under, and con-
centrlcal with il, is placed a circular table.
some twenty feet in diameter the crcumter-
ence of which is divided into degrees, minutes,
&C, and the divisions numbered. Now, it can
be shown by the most elementary principles of
mechanics, that supposing the earth 10 have
the dlurual motion upon its axis which is i'm.
puted to il, and which explains tho phenomena
OF day and night, &c, the plane in which this
pendulum viOra'cs will not be affected by this
dIurna motion, hut will maintain strictly the
same direction during twenty-tonr hours. In
lhls interval, however, the table over which the
pendulum is suspended will continually change
Its position in virtue Of the diurnal motion, so
as 10 make complete revolution round its
centre.
Since, then, the table thus revolves and the
pendulum which vibrates over it does not re-
solve, 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 10 minute and from
hour to hour, 50 that if such point were a pen
cll and that paper were spread upon the table,
the course formed by this pencil during twenty-
four hours would form a system of lines radia-
lng from the centre of the table, and the two
lines formed after the interval Of one hour wond
always tnrm an angle with each other of Is : :,
being the cath part Of the circumference Now
this is rendered actually visible to the crowds
which daily flock to the Pantheon to witness
TINS remarkable experiment. The practiscd
eye of correct observer, especially if aided bv
proper optical instrument NAV actually see
the motion which the table has in common
''''' '''N '"''', "i'ut' lIlc ptHuuIuIl, DelWeeU
two successive vibrations. Il is, in fact, appa-
rent that the ball, or rather the point attached
TO the ball, does not return precisely to the
same point OF the circumference of the table
ai'er two successive vibrations. Thus is rem
dered visible the motion which the table has in
common with the earth.
1t is true that, correctly speaking, the table
does not turn round its own centre but turns
round the axis of the earth; nevertheless, the
effect of the motion relatively L. the pendulum
suspended over the centre of the table, is pre-.
cIseIy the same as it would be il 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 eartb's axis, the point Of Suspension of the
pendulum is turned also IN the same time round
the same axis, teing continually maintained
vertical above the centre of the table The
plane in which the pendulum vibrates does not,
however, partaEe Of this motion, and, conse-
quent!y, has the appearance of revolving once
in twenty.iour hours over the table, while, in
reality it is the table which reyolves once in
twenty-iour hours under it.