bodkin, or an Indian club, in which the sun stands for the knob
(disproportionately big), the inner planets for the handle, and the
outer for the blade or body. Again, the average density of the inner
planets exceeds that of the outer by nearly five to one, but the mass of
any planet is greater than the combined masses of all which are smaller
than it. The inner planets derive all their light and heat from the sun,
and have few or no satellites; whereas the outer, to all appearance, are
secondary suns, and have their own retinue of worlds. On the similitude
of a clan or house we may regard the inner planets as the immediate
retainers of the chief, and the outer as the chieftains of their own
septs or families."

"How do you account for the symmetrical arrangement?" I enquired.

"The origin of the solar system is, you know, a mystery," replied the
astronomer. "According to the nebular hypothesis we may imagine that two
or more dark suns, perhaps encircled with planets, have come into
collision. Burst into atoms by the stupendous shock they would fill the
surrounding region with a vast nebula of incandescent gases in a state
of violent agitation. Its luminous fringes would fly immeasurably beyond
the present orbit of Neptune, and then rush inwards to the centre, only
to be driven outwards again. Surging out and in, the fluid mass would
expand and contract alternately, until in course of ages the fiery
tides would cease to ebb and flow. If the impact had been somewhat
indirect it would rotate slowly on its axis, and under the influence of
gravity and centrifugal force acquire a globular shape which would
gradually flatten to a lenticular disc. As it cooled and shrank in
volume it would whirl the faster round its axis, and grow the denser
towards its heart. By and by, as the centrifugal force overcame gravity,
the nebula would part, and the lighter outskirts would be shed one after