Bristol news. [volume] (Bristol, Va. & Tenn.) 1867-189?, 1871-02-24

cohOl, OF which the lower strata are
heavier than the oil, while the upper
strata are lighter. The oil, when poured
in, descends until it reaches the stratum
of the same density, when being freed
from the action Of terrestrial gravity,
and subjected only to the mutual al
traction of its own molecules, il as
sumeS Il spherical cOntriVanCe, NJ.
Plateau now causes the sphere of oil
t. rotate about its own centre of graV.-
ty. While the movement Is slow, the
excess Of centrifugal force at t1.e equ2-
tor Of the Oil-globe causes a bulging Of
the equator and corresponding flatten-
ing OF the poles, like that OF served
in the sun and III all the plane Is
From sphere the oil-glObe becomes
"spheroid of revolution" If now
the movement is considerably accelcr;-
ted, the equatorial portion of the oil
globe becomes detached, and sur
rounds the central sphere of oil in the
shape of a nearly circular ring, like
Saturn's ring system. Finally, if the
movement is kept up for Il sut1i-
cient length OF time, the OF ring breaks
into fragments, which revolve like s;,-
elites about the Oil-glObe, and each o.
which Keeps up for a time its ov n
movement of rotation ia the same Ill
rection with the revolution of the rim"
The common origin of tie plane :
from the suns equator, AZ thus Strik
ingly illustrated, explains at once the
otherwise ineXplicable coincidence o.
their rotations, their revolutions, and
their Orbital planes. At single glance
we see why the planetary orbits are al
ways nearly cOnccI tric, and nearly in
Il plane with the solar equator; and
we SET that since the sun has rotated
from west to east since the beginning.
the planets formed from him must
have kept upa revolution, and acquired
a rotation, in tEe same diTCt ton.
But the evidence i'm favor of lap
lace's theory is not restricted u tie G.
general condolences between OlscFva-
ton ana deduction, and Laplacc him
self 10y 10 means stopped short at this
part Of the inquiry. Many striking
miner details in the present structure
of the solar system, otherwise appaT-
emily ineXplicable, are beautifully eX-
plained by the theory OF nebular gene
sis. For example, Uranus rs already
observed, while revolving in the same
direction with othe- planets, has aS a
backward rotation, 80 that To an iHhah.-
tant of Uranus the sun would sttm 10
rise in the vest and set in the east. His
moons revOlvc about him in the same
r,trOeade direction and his axis. /, o.
stead of sta ding at a great angle to
his Orbit-planC, rs is the case with She
other planets, lies down almost uEoI.
the Orbit-plaue. These pcculiarijjc>
are probably shared by Neptune. Why,
then, are the two outermost p ancts t!I-
ped over i'm this uusremiy way? Mr..
Spencer has shown that the earlier
rings detached from the solar sphcToid
must have been shaped like very thin
hoops, 81 that the VelOcitieS of their
inner and outer surfaces must have
been nearly equal : and the resulting
planets consequently having Their
greatest diametCrS al right angles to
the plane Of their orbits, must have
had Il tendency to rotate in a plane
nearly perpendicular to their orbits,
and in Il direction not related to thciI
orbitual, revolutions. But as the solar
spheTOid continued to contract its i'll
creasing equatorial velocity rendered
it more and more Oblate in figure, 80
that the later rings detached from il
were qu0it-shaped. and the result
ing planets appeared with their great
est diametcrs but little inclined to tie
planes of their orbits and were hence
preserved from any tendency to Il ret
rogade rotation. BY this brilliant eX-
PLANTATION, an apparent difficulty in
the way o. the Nebula Hypothesis is
converted into a powerful argument in
its favor. But still further valuable
service i rendered by Mr.. Spencr's
suggestion.
According 20 the Nebular Hypothe-
sis the outer planets ought in general
to be much larger than the inner
planets ; and for very simple reason.
The ancestral ring which coiucided
with the immense orbits of Uranus
and Neptune must, Of course, have
been larger than the ancestral rings
which conceded with the comparative
ly small orbits of Mars and the Earth.
The ring which resulted in Neptune
was nearly eighteen billions Of miles
in circumference. while the ring which
resulted in the Earth had circum-
of less than six hundred millions of
miles. Obviously, therefore, Neptune
ought to he larger than the Earth, as
in fact it is.
But this explanation is not COM
plete As our case now stands, there
ought TO he regular gradatiOn i'm thc
sizes of the planets. The OutermOst
one shonld be the largest, and the
innermOst one the smallest. The facts
do not quite correspond With this re-
quirement. The four outer planets are
indeed much larger Nhan the four in
ner ones; but of the inner group the
largest is not Mars, but the Earth;
while in the outer group we find Ju-
piter three and half times as large as
Saturn, which in turn is seven times
larger than Uranus. The cause of these
apparent anomalies in the outer group
is to be sought in the excessive thin
ness of the hOop-like rings from which
the two oldest planets were formed.
On the.Other hand, the ancestral rings
of Jupiter and Saturn. though many
times smaller in circumference. must
have been exceedingly broad and rath-
ct thickquOit-shaped rings, con-
tanning more planetary matter than
the extensive but slender hoops which
had preceded them. Thus the size of
the planets depends on at least two
factOrs-the ciTcumfeTeHces Of their or
bits and the shapes Of the rings
from which they were formed. The
extreme smslln0ss of the inner plan
Earth, VeTus, and Mercury
is due to the smallness Of their o.
bits, combined with the slightly hoop
ed shapes of their ancestral rings; that
Of Mars being probably the most sleE-
der OF the four
Curiously enough, if we examine
the different systems OF satellites, we
find the same general contrast in size
between the members Of oJtcr and in
Her groups. Uranus and Jupiter have
each four satellites; and IN each case
the two outer ones are much larger |
titan the two inncrO ones. or the eight |
satellites Of Saturn, the three outer |
ones are very large, while the five iu-
ner ones are small. Moreover the !
largest Of Jupiter's moons is not The |
eighth. bu the sixth, which has a di- |
ametCr considerably greater than that |
Of Mars. These curious condolences |
point 10 a common mode Of nebular |
genesis. They appear 10 show ihat. |
A. a general rule, the rings, successive