40 D. Trowbridge on the Nebular Hypothesis. 
much flattened about the poles. If the rings of Saturn are Aid, 
they exist as such in consequence of the friction of es 
particles. | 
58. It is an interesting fact, and one confirmatory of our the 
ory, that the rings of Saturn have a longer period of rotation 
than the planet itself, as required by the nebular hypothesis. 
According to the observations of Sir William Herschel, the 
rings of Saturn revolve around the planet in the space of 108 e 
32 158." The period of rotation of Saturn is 10h 29m 1788 
We thus see that the rings require 2™ 58s longer Son to revol¥e 
ans sasigait ve the latter does to turn on his axis. Here 
agai appear to have obtained conclusive evidence in n favor 
of the ee don seni ey Had the period of Saturn’s rotation 
been greater than that of the rings, it would have been Mas 
difficult to reconcile it with the nebular hypothesis. 
59. The rings of Saturn are either fluid or composed of un 
connected particles. According to Maxwell, even a fluid ring 
would be broken up into small ‘satellites ; but it does not follow 
that these satellites may not still be fluid and unite again into @ 
ring—or perhaps several nearly concentric rings—after having 
been separate a sufficient length of time to restore the equilib 
rium by counteracting the disturbances to which the ri ngs are 
subject. We are thus reduced to the very probable conclusion | 
that eon rings of Saturn are fluid (liquid). We are thus ca 
reat step toward the gaseous condition from which 
- have sspposed all the planets a their satellites to have beet” 
ob 
60. Observation shows that the satellites of Uranus revolveia 
a retrograde order. But we do not know in what direction, not” 
clination to the plane of the orbits of the satellites differing con 
siderably from a right-angle, the difficulty will not be insuper 
able.“ But since the nebular hypothesis accounts so satisfae . 
torily for so many of the phenomena of the solar system, W' we 
may venture to predict that the rotation of the planet will bi 
to be retrograde, or closely Fg ws that direction, i 
we may so express ourselves. But our theory, as we hawt 
Grant’s 2 
= eect 
gc — ificial glo be a motion of rotation on its axis, and then md 
the gg fer how | sama the direction of rotation is angel to = 
opposite direction. impetus carries it in the op) 
a ee eee 
Pehiiee eM als 
