t if the theory were the correct explanation,
the various orbits of the planets would be much more nearly circular
than they are.

It is also thought that such interlaced paths, as those in which the
asteroids and the little planet Eros move, are most unlikely to have
been produced as a result of Laplace's nebula.

Further, while each of the rings was sweeping up its matter into a body
of respectable dimensions, its gravitative power would have been for the
time being so weak, through being thus spread out, that any lighter
elements, as, for instance, those of the gaseous order, would have
escaped into space in accordance with the principles of the kinetic
theory.

_The idea that rings would at all be left behind at certain intervals
during the contraction of the nebula is, perhaps, one of the weakest
points in Laplace's hypothesis._

Mathematical investigation does not go to show that the rings, presuming
they could be left behind during the contraction of the mass, would have
aggregated into planetary bodies. Indeed, it rather points to the
reverse.

Lastly, such a discovery as that the ninth satellite of Saturn revolves
in a _retrograde_ direction--that is to say, in a direction contrary to
the other revolutions and rotations in our solar system--appears
directly to contradict the hypothesis.

Although Laplace's hypothesis seems to break down under the keen
criticism to which it has been subjected, yet astronomers have not
relinquished the idea that our solar system has probably had its origin
from a nebulous mass. But the apparent failure of the Laplacian theory
is emphasised by the fact, that _not a single example of a nebula, in
the course of breaking up into concentric rings, is known to exist in
the entire heaven_. Indeed, as we saw in Chapter XXIV., there seems to
be no reliable example of even a "ring" nebula at all. Mr. Gore has
pointed this out very succinctly in his recently published work,
_Astronomical Essays_, where he says:--"To any one who still persists in
maintaining the hypothesis of ring formation in nebulae, it may be said
that the whole heavens are against him."

The conclusions of Keeler already alluded to, that the spiral is the
normal type of nebula, has led during the past few years to a new theory
by the American astronomers, Professors Chamberlin and Moulton. In the
detailed account of it which they have set forth, they show that those
anomalies which were stumbling-blocks to Lapla