l differ from it less.

Here, again, inference to a considerable extent agrees with observation.
Though the progression is irregular, yet, on the average, the
inclinations decrease on approaching the Sun; and this is all we can
expect. For as the portions of the nebulous spheroid must have arrived
with miscellaneous inclinations, its strata must have had planes of
rotation diverging from the average plane in degrees not always
proportionate to their distances from the centre.

* * * * *

Consider next the movements of the planets on their axes. Laplace
alleged as one among other evidences of a common genetic cause, that the
planets rotate in a direction the same as that in which they go round
the Sun, and on axes approximately perpendicular to their orbits. Since
he wrote, an exception to this general rule has been discovered in the
case of Uranus, and another still more recently in the case of
Neptune--judging, at least, from the motions of their respective
satellites. This anomaly has been thought to throw considerable doubt on
his speculation; and at first sight it does so. But a little reflection
shows that the anomaly is not inexplicable, and that Laplace simply went
too far in putting down as a certain result of nebular genesis, what is,
in some instances, only a probable result. The cause he pointed out as
determining the direction of rotation, is the greater absolute velocity
of the outer part of the detached ring. But there are conditions under
which this difference of velocity may be too insignificant, even if it
exists. If a mass of nebulous matter approaching spirally to the central
spheroid, and eventually joining it tangentially, is made up of parts
having the same absolute velocities; then, after joining the equatorial
periphery of the spheroid and being made to rotate with it, the angular
velocity of its outer parts will be smaller than the angular velocity of
its inner parts. Hence, if, when the angular velocities of the outer and
inner parts of a detached ring are the same, there results a tendency to
rotation in the same direction with the orbital motion, it may be
inferred that when the outer parts of the ring have a smaller angular
velocity than the inner parts, a tendency to retrograde rotation will be
the consequence.

Again, the sectional form of the ring is a circumstance of moment; and
this form must have differed more or less in every case. To make this
clear