e that their present
arrangement is derivable in any way from an explosion, and it is certain
that an enormous time must have elapsed since such an event if it ever
occurred.

It is far more probable that they never constituted one body at all, but
are the remains of a cloudy ring thrown off by the solar system in
shrinking past that point: a small ring after the immense effort which
produced Jupiter and his satellites: a ring which has aggregated into a
multitude of little lumps instead of a few big ones. Such an event is
not unique in the solar system; there is a similar ring round Saturn.
At first sight, and to ordinary careful inspection, this differs from
the zone of asteroids in being a solid lump of matter, like a quoit. But
it is easy to show from the theory of gravitation, that a solid ring
could not possibly be stable, but would before long get precipitated
excentrically upon the body of the planet. Devices have been invented,
such as artfully distributed irregularities calculated to act as
satellites and maintain stability; but none of these things really work.
Nor will it do to imagine the rings fluid; they too would destroy each
other. The mechanical behaviour of a system of rings, on different
hypotheses as to their constitution, has been worked out with consummate
skill by Clerk Maxwell; who finds that the only possible constitution
for Saturn's assemblage of rings is a multitude of discrete particles
each pursuing its independent orbit. Saturn's ring is, in fact, a very
concentrated zone of minor asteroids, and there is every reason to
conclude that the origin of the solar asteroids cannot be very unlike
the origin of the Saturnian ones. The nebular hypothesis lends itself
readily to both.

The interlockings and motions of the particles in Saturn's rings are
most beautiful, and have been worked out and stated by Maxwell with
marvellous completeness. His paper constituted what is called "The Adams
Prize Essay" for 1856. Sir George Airy, one of the adjudicators
(recently Astronomer-Royal), characterized it as "one of the most
remarkable applications of mathematics to physics that I have ever
seen."

There are several distinct constituent rings in the entire Saturnian
zone, and each perturbs the other, with the result that they ripple and
pulse in concord. The waves thus formed absorb the effect of the mutual
perturbations, and prevent an accumulation which would be dangerous to
the persistence of the w