American citizen. [volume] (Butler, Butler County, Pa.) 1863-1872, 1864-03-23
Educational Department,
The Rotation of the Earth,
DEMONSTRATED BY THE PENDULUM

DEMONSTRATED BY THE PENDULUM.
In 1851, the scientific world were much
occupied with discussing the merits of "a
new mode of demonstrating the earth 5
diurnal revolution, discovered by VI. Leon
Foucault, of Paris. Although the very
general interest which his discovery then
elected, has long since given place to the
excitement incident to fresh discoveries,
yet we are confident that some (particn-
larly Teachers) may still be interested, if
not benefit, by repetition of the expert
ment of NJ. Foucault, and review of the
demonstration based upon it.
The simplicity and conclusiveness of
the latter, commend it to all, indeed, who
appreciate the Baconian orinductive meth
cd of investigating nature; whilst its
mechanical character renders it invalu,,-
bic to the Teacher or Lecturer, as a means
of exhk2ting ocularly a fact already fully
established by abstract reasoning, based
upon the known principles of physics
These considerations are our justification
for again calling the attention of educa-
tors and others to this subject.
The fact underlying said demonstra-
tion is, like all important facts in science
simple; inasmuch as to excite considera-
BILE wonder that it should so long have re
mained unnoticed 1t is as follows: A
pendulum so suspended as to move freely
IN all directio Is, will, if made to vibrate
across graduated circular table, continu
ally change its path in reference to the
plane over which it is moving; so that in
a certain period, of which the length is
determined by the latitude of the place
where the experiment is made, it will. ap-
parently have described complete revo-
luton around the circle across which it
has been vibrating; and the devotion will
be uniform for each degree of latitude,
but its rate will regularly diminish. from
the poles to the eXuator, where it be
comes equal to O. whereas the time of one
completerevolution of the pendulum rcgu
larlp increases from the poles, where it l.
"A hours, to the equator; where it equals
infnity Furthermore, the deviation is
in opposite direction on opposite sides Of
the equator; being. in the northern hem
sphere, from west to east, q. e. in the d..
rection of the hands of watch) an
from east to west in the southern.
The reader may be readily. convinced
Of the reality of thefe interesting phe
nomena, by instituting the following sim
pie experiment.
From the ceiling of high room, sus
pen globular weight of about six pounds
by means of a slender wire, Of such lenth
that the weight, wH6n at rest, may stand
about one inch above the floor The wire
should be so attached to the ceiling as not
to prevent the gyratcry motion Of the
pendulum. Next, describe upon the floor
a circle of convenient dimensions, say from
to 16 feet in diameter, having its centre
directly under the point of SUSPENSION
| Divide the circle into certain number of
equal parts, dy lines passing through the
centre and terminating at both extremi-
ties in the circumference; or (Which is
better divide the circumference, or por-
tion of it, into degrees, minutes, ETC., num-
bering the divisions.
Things being thus arranged, let the ex-
perimenter carefully draw the pendulum
to convenient point in the circumfer-.
ence, and by means of slender thread,
fasten it to some object, say or block, stand
ing outside the circle. When it has come
to a state of perfect rest, he may then
suddenly, but dexterously sever the thred
by burning it. The pendulum will, OF
course, descend along one Of the diane
,ers of the circle, pass over the centre
point opposite to that from which is star
ted From thence it will apparently re
turn, by the same path, to the same point
Of rest but after few vibrations, it will
become evident that the pendulum con-
stantly changes its path In reference to
the circle; always cutting the circnmfer-
ence on the right OF the point of rest to
an observer on the opposite side, and on
the LEFT of that point to an observer on
the same side. With large circle, tel
minutes of time is sufficient to show de-
Walton of several inches but if the Vi
brations be continued without Interrupt
ton, in about SO hours Gin our latitude
the pendulum, after having passed sue
cessively over every portion Of the cir
cumference, will move along the first di-
ameter again. By this movement-sub
lime, because compelled by the omnipc-
fence of Divine LAWS chronicled the
hourly motion of the earth upon her axis