Weekly national intelligencer. [volume] (Washington [D.C.]) 1841-1869, 1851-09-13
FROM A SCIENTIFIC CORRESPONDENT.
eaF TO THE EDITORS.

The Pendulum Experiment. which is said prove the
voution Of the earth its axis, will appear simple
examine the elementary principles, by one, which it
combines FIRST the position Of the circular board in
spect the axis Of the EARTH which board marks the variation
of the pendulum secondly the susceptibility Of the pendu
lum to motion, and the forces which act upon it.
circular board, fixed to the earth in the horizon6rs
extremity Of the earths axis secondly, point
the equator and thirdly, at intermediate point
the surface Of the earth, sufficient to explain the rule in
every For in the first case, the board is right angles
the axis of the earth and, having s axis in the
straight line with that Of the eah makes revolution about
its axis in with the earth In the second has
the Of the earth PARALLEL and consequently the revolution
earth about it's axis does produce any revolution Of
the board about its axis but motion Of the WHOLE and
every particle Of the board in the direction and with
the velocity In the third case, intermediate
point has the axis Of the earth obqus and the board is
under the influence of rces the tendency Of Of
which is drive the board round in the first tho
ether 10 the second The force in the second does
not affect at all the revolution Of the board about its
ss in the first it does, and acceerates the revolution d.
recy the angle made by the axis of the earth with the
plane Of the board increases So that have this general
rule 900 is to the latitude which the board is placed
revolution is to the part Of revolution which the board
will make in one day at the given place.
Secondly. The pendulum suspended by.a thread and
is drawn towards the centre Of the earth by the force Of ga
viy The forces upon the pendulum upon the
board and the result is the that s the revolution of
the pendulum upon its axis which is the line Of the
thread n the time that Of the board and forward
motion like that of the board force isl applied to the
pendulum This force becomes expended at the extremity OF
the arc where the pendulum is left to the force OF gravity
alone to kept motion The rule that the force Of gravity
4 froun tho
ire Of the earth increases shows that in whatever plane h
pendulam vbrates the Of gravity is the sameat points
equally distant from tho Of the earth, and therefore
equally distant from the Of the in the n of the
arc whence follows that the force Of gravity des ope
rate Al all to change the direction Of the plane which the
pendulum ybrates although such constan, change eqsed
to make the arc and xed line ihe board correspond for
If should operate change the direction of tia plane the
force Of sravy would be distributed and that Properly called
gravity the measure Of which weight wouldbs danished
contrary to the general rule. al s8i IN
There as ,hen the following fssces whish give motion
to the pendulum FIRST attraction e srsvaon, wAeh
equal force all points equsy distant foaa NJ centre
the eaph and does not therefore, conns the vbs tons of
the pendulum given plane, prevent THEN ch
any plane which passes through the csnsss Of tie earth
and the point Of suspension Of the psnduiuS secondly
the forward motion of the EARTH and the forward motion of
the surface OF the earh IN boan OF Wnscn ns pendulum
carried on by Of attraction Of gavsto and the point
Of suspension being fixed to the earth and thirdly the ro-
ay motion Of the surface Of the earth ii he given point in
common with the board and the pendulum ITSELF which force
il not destroyed continues to act according the laws Of
tay motion the pendulum when detached from the surface
Of the EARTH and therefore cannot affect II oil the position Of
the arc.
IF the above statements accurate, and involve all the
principles which affect the pos Of the arc described by
the pendulum, follows that there force bring and
hold the in the plane with that Of fixed line upon
the board. ,t ss tt L.