New-York daily tribune. [volume] (New-York [N.Y.]) 1842-1866, 1850-11-23
THE EARTH-lTS MOTIONS

BY Professor o NJ NtTcarL Of Cincinnati.
LReported for The Tribugsl

auspices ot tue BROOKLYN Astronomical sg.;,,
was delivered at the Female Academy ~, Tim:
day evening. Previous to tue appearance ~ -.
lecturer, Rev. Dr. Cox in behalf Of ,hs conro;1 IS
the astronomical society, announced that after tho
lecture on next Monday evening there would IA
opportunity for those who had not become
members to subscribe to the association. He said
that though many had already joined in the work
he bad no doubt but many more would gladly Do
so and urged upon the present members aprnnpt
payment OF their subscriptions that Instruments
Of the first class might be at once ordered 20 be
constructed while the other portions Of the work
were accomplished The two lectures IN the
week after next he said were to be on the organ,
ization and wants of an Observatory and the So
ciety did not intend that the Observatory of Cam
bridge which has recently discovered third ring
to Saturn and new satellite to the same planet
shall find all the wonders of the Heavens before
their own Is erected, equipped and manned,
Professor Mitchell commenced by saying that be
wished to direct the attention OF his hearers to
planet first discovered he believed, by Copern
Gus. That planet our own Earth. That the
Earth with its vast oceans streams plains and
population, should really be moving body
wanderer moving around a distant orb with in
mense velocity was a fact hardly to be realized
When we behold a locomotive flying past u.s. a
mile in minute, instmctvely draw back
with dread. But If we could see this great
Earth, with its towns and cities, nations and peo-
pie, sweeping past with a thousand times ereater
yeocity-wlth such speed that even thought
cannot keep pace with tive cannot realize what
emotions wodld be excited. 1t was not strange
that the assertion OF such theory by C0pernicus
astonished the philosophers of his day. The mo-
ton of the Earth could not be seen, heard or
felt the testimony of all the senses was against
it, and it was directly controverted by phioso
ply which had combined with and tostered the
prejudces of men for thousands OF years. All
honor is due to him who broke through the bar.
riers of prejudice united the Earth to the number
of the planets gave her orbit, and assigned her
place in the heavens. His announcement was
of a magnificent discovery 1t reated to motions
and dimensions of immensely. The philosophers
attempted to overthrow it by reasoning They
said &" If the Earth moves, as you assert, in an
orbit of goo 600 of miles in diameter, Its pole
will to pont spot in the heavens which Will move
in circle of the same diameter, whereas the pole
always points to the same star Now this was
conclusive, and there was no way OF evadlng this
reasoning till it was found that If globe as large
as the Earths orbit placed at the distance
of the nearest fixed star 1t would to US appear 50
minute that the most delicate instruments could
show no measurable diameter. How vast the
plan, when the nearest stars are so distant from
each other that 200 100000 miles appears an In
appreciable point
The lecturer announced that he should in this
"a task by no means easy to perform. Though
all might implicitly believe the fact, few could
give reason for such belief, except conf.
dence in the instruction OF others. lie would en-
deavor to show that the Earth had three distincs
motions one, rotation upon its own axis Whlca
always maintains its position, IN the earth-a Fo-
lotion OF this axis describing III space cOncai
fgure-and revolution round the Sun. These
facts be should not attempt to show In the ordl
nary manner by saying that it was impossible to
conceive of all the heavenly bodies revolving
round the Earth for it was possible to conceive OF
amy thing He could prove 1t IN different man
ner.
The lecturer then referred his hearers to those
laws of gravitatOn, and of the composition Of
forces, which he had explained In his previous
lectures. From the operations OF these laws he
would deduce the fact OF the earth's motion upon
its axis.
That the figure of the earth is nearly spherical,
was one of the earliest facts established by ha.
tronomy The eclipses of the Moon show that as
well as various other indications, but its exact
figure and size could be learned by the obserya-
ton of the stars. If we observe the ster directly
over US, and go North, we shall ind 1t TO decline
toward the South, and another star occupies the
zenith. If we continue round the earth our
zenith or the point directly above US, VIII
have passed through the whole circle OF $50
degrees, returning to the same star AGAIN
II, however, we pass but small distance,
the proportionate part OF the heavens between
the earth and the star first Observed will
indicate the portion OF the Earth's circumference
travelled The part thus obtained giyesthe whole
of the Earths circumference and from that by the
aid OF Geometry the diameter is calculated NOW
suppose body composed like the Earth to Do
sperical and at rest, there would be no chenge IN
its form but let it be made to rotate and the cen
trifugal force would cause every particle whicn
was free to move to seek the central portion, az
the greatest distance from the axis. The oceans
would at once leave the Poles and rush 10 Sh9
Equatorial regions By their action upon the iand
they would change its form and it would De acCa-
mulated there and this change would cohehualg
go on increasing the Equatorial crcumierehce aho
1attening the Poles until some coumCefactn3 iotGo
should restore an equilibrium. Ihis would taKe
place when the centrifugal force should be 0a'aa'
ced by the extraction 30 be overcome III rising
the hill made by the inrcre ased diameter at the
eorator What this form would be in a body r0-
tating with given velocity is easily calculated
from the known laws OF attraction and notion
Sir Isaac Newton computed what the Earths
figure ought to be to correspond with the astro'
nomical theory long before it was known, and 1t
has since been found to correspond with hls re-
suits That the figure OF the Earth Is spheroldai
with its polar diameter about 20 miles less than
its equatorial has been tested in the same way
that the Moon was weighed on the principle
that the distance body falls in a second IS ing
measure of the force exerted upon it. pendi'
lum was used as the falling body and the proper
tonate length OF strokes gave the attractive
power. From the difference between that Of
high and low ATTITUDES, the experiments took the
effect Of the difference OF centrifugal force which
was known, and the remainder showed the differ
ence in distance from the center Of the earth.
The figure of the Earth being established, It
becomes certain that it could not remain what u
is if it did not rotate on its axis.
The lecturer stated that there we're no apP[ecia,
Bile causes to interfere with this continued and
Incidentally in this connection he explained
the trade winds as being caused by the dense
centrifugal force, the equator and the still sag.
gine behind the earth in It's motion in consequences
Of he Lesser rate OF speed derived from the mo-
The second .s motion of the Earth is that Of IT,
:.i r,nrt IN the heaYens By which il