ituting the known planetoids, varying from some 200 miles in
diameter to little over a dozen, there would be sent out still more
multitudinous portions of the crust, decreasing in size as they
increased in number. And while there would thus result such masses as
occasionally fall through the Earth's atmosphere to its surface, there
would, in an accompanying process, be an adequate cause for the myriads
of far smaller masses which, as shooting stars, are dissipated in
passing through the Earth's atmosphere. Let us figure to ourselves, as
well as we may, the process of explosion.

Assume that the diameter of the missing planet was 20,000 miles; that
its solid crust was a thousand miles thick; that under this came a shell
of molten metallic matter which was another thousand miles thick; and
that the space, 16,000 miles in diameter, within this, was occupied by
the equally dense mass of gases above the "critical point", which,
entering into a proto-chemical combination, caused the destroying
explosion. The primary fissures in the crust must have been far
apart--probably averaging distances between them as great as the
thickness of the crust. Supposing them approximately equidistant, there
would, in the equatorial periphery, be between 60 and 70 fissures. By
the time the primary fragments thus separated had been heaved a mile
outwards, the fissures formed would severally have, at the surface, a
width of 170 odd yards. Of course these great masses, as soon as they
moved, would themselves begin to fall in pieces; especially at their
bounding surfaces. But passing over the resulting complications, we see
that when the masses had been propelled 10 miles outwards, the fissures
between them would be each a mile wide. Notwithstanding the enormous
forces at work, an appreciable interval would elapse before these vast
portions of the crust could be put in motion with any considerable
velocities. Perhaps the estimate will be under the mark if we assume
that it took 10 seconds to propel them through the first mile, and that,
by implication, at the end of 20 seconds they had travelled 4 miles, and
at the end of 30 seconds 9 miles. Supposing this granted, let us ask
what would be taking place in each intervening fissure a thousand miles
deep, which, in the space of half a minute, had opened out to nearly a
mile wide, and in the subsequent half minute to a chasm approaching 3
miles in width. There would first be propelled through it enormo