'§2 A! Hinrichs on the Density, Rotation, and Age of the Planets. 
The planets near the sun, A>c, have a DIRECT rotation, which 
disappears at a certain distance from the sun (A=c) and is followed — 
by @ RETROGRADE motion of all the more distant planets (having 
a<¢). ; 
: The great discovery of Herschel, far from being opposed to the : 
nebular hypothesis of Kant and Laplace, on the contrary affords. 
a most interesting and decisive confirmation of it, and makes ib 
even similar to a most remarkable proposition in the theory of 
gravitation. For in the latter the orbit will be an ellipse, 4 
rabola or a hyperbola, according as the centrifugal force was 
ess, equal to, or greater than a definite quantity ; so here we Se 
the direction of rotation determined in the very same manner, 
he motion of the moons of Uranus is consequently for the ; 
nebular hypothesis exactly what the nearly parabolic orbits of, 
comets are for the hypothesis of gravitation. If the density 4 
ad been excessively small, all the planets might have beet 
retrograde in their rotation, although they would have had @ 
direct revolution. a 
The velocity of rotation depends upon W and the mass of a 
planet; we cannot here determine it. But we can show how the 
position of the axis of rotation will vary. For if—as is highly 
probable—the ring was not quite symmetric with regard to the 
lane of the orbit, then there will be a difference of vis viva W, 
tween these two sides, tending to produce rotation around af 
axis in the plane of the orbit. Hence the position of the axis of 
rotation of a planet will be determined by 
tani) (25) 
t being the angle between the equator and orbit of the planet, 
As the direction of the axis W, only determines the position of 
the nodes of the equator, we must here consider W , a8 positives 
as been found to change sign at a certain distance in becom: 
ing negative; so that we see: all planets inferior to Uranus have 
tdcute, superior to Uranus i must be obtuse. The determination 
of the exact position of the axis of Neptune” will therefore be 
of great importance as a test of this remarkable Jaw. __ 
rigin of the tangential force—As now the contradictions bof 
tween observations and the theory of Kant and Laplace prove Lt 
be but apparent,-founded in the neglect of the theory by mathe 
maticians; we may inquire into the cause of the primitive | 
motion of the nebulous sphere. ma 
_ Attractive particles (m) alone cannot give rise to a couple ¢ 
forces; neither can repulsive particles (u) do it—but by t® 
' ™* Humboldt gives i=84° 7’ for Neptune, but does not state whether the mete 
is direct or not, It must be retrograde or i=145° 53’‘—Cosmos, iv, 181. (Ha 
