Weekly national intelligencer. [volume] (Washington [D.C.]) 1841-1869, 1851-05-31
COMMUNICATIONS.
ROTARY MOTION OF THE EARTH.

Of Wednesday article signed p, in which occurs The
following:
some thing will say that have not noticed in any
the poles the rotary motion Of the earth is shown
by the pendulum and in all intermediate points between the
poles and the EQUATOR and not at the EQUATOR per
sons suppose then the pendulum shows only the rotary
motion Of the earth, but that is round from north to SOUTH
Being myself of those who suppose above stated
should be extremely obliged p, any other learned gentle
man. would be 10 kind for three questions
ls Whether the pendulum vbrates accurately and with
out variation in The line Of the equator
Cd Whether the pendulum vbraes at the poles with uni
form variations and FORM by the lines Of motion,
rays in equal distances from each other and in all directions
from the pole
3D. Whether the figure described by the pendulum at the
poles is reduced the single line at the equator gradually
and SO that by the degree Of the change given place,
may be indicated the latitude Of the place G.
M. FOUCAULTs DEMONSTRATION OF THE
EARTHS ROTATION.
Messrs EDIToRs Rarely has happened that any ques
ton in mechanical philosophy has generally attracted the
attention Of the public has the beautiful pendulum expert
of M Foucault for making the rotation Of the earth
upon its axis visible the eye To many minds however,
as learn from your correspondent "Inquer" and other
the explanations that have been published Of the phe
nomenon entirely satisfactory At the instgaton OF
friend therefore, will the following illustrations,
which you may publish you think them likely to clear up
any difficulties in the minds Of any Of your readers
Let us suppose esden ball to be suspended by thread
from the ceiling Of railroad When the running
straight track this suspended ball may be made to osci-
exactly the rest and if chalk line were
drawn on the floor Of the car the direction Of the osca
TONS il would continue to oscae along that ne But if
the car run on curve is only carried forward, but
oft of
the ball. however, will remain unchanged, and consequently
longer oscillate along the chalk line but will
cross it at ANGLE thus indicating the turning Of the
Now this is precisely analogous to the of Foucaus
experiment. The room, we will say, in which the expert
men is conducted is by the earhs rotation, carried
parallel Of latitude in the the over rail-
road AT the equator the motion straight track
tina, is curvng either the right left the parallel
of latitude does consequently there rotation about
vertical line The equator only in vertical plane
follow the rotundy of the EARTH and this, in Of
making the experiment there, would impar to the room
tng motion, like that which carriage would have in going
the summit Of hill; but it is susceptible OF demonsra-
ton that this fitting notion which also takes place in less
degree parallel Of latitude, has effect in changing the
direction Of the oscillations. If line drawn the
floor table in the direction Of the oscillations, then at the
equator the pendulum would continue osciate along that
line notwithstanding the tilng motion but parallel Of
latitude would depart from it. in consequences Of the hon
zona rotation Of the room above explained and at rate
exactly equal the rapdy Of that horizontal rotations and
such that the line plane Of oscillation would travel COM
petely around circle drawn the floor in % hours Sc
minutes, he sderea real time Of the earths revolution
on It's axis multiplied by the cosecant Of the latitude In
latitude 80 degrees of which the cosecant p the time
would be sdereal days. Az hours 50 minutes In the
latitude Of Washington, which, according to an atlas before
me- is SO degrees 81 minutes, it would be 80 hours
minutes.
There is no such thing as fixed direction in absolute
space in which the pendulum always osclates this being
rendered impossible by the constant fitting motion or change
in the absolute direction Of the perpendicular But this as
lust explained does interfere with the manner in which the
plane Of oscillation makes its way from minute to minute
around the circle on the floor.
In regard the question Of the necessity that the point Of
suspension should be movable about vertical axis has
been well observed that that has nothing to do with deter
mining the direction motion Of the plane Of oscillation, but
can only affect the rotation Of the pendulum about its own
axis which rotation sensby Independent Of the oscillations
of the pendulum This will be readily understood if il is
considered that the pendulum might even spin around with
some rapidty when suspended by twisted thread and
vet oscae and undergo the apparent change in the
direction Of its oscillations, illustrated by the suspended
bullet on the railroad car J. H. -
WASHINGTON, MAI y, 1851.