We must not fail to mention, however, that there is a rival hypothesis
which commends itself to many astronomers -- viz., that the asteroids
were formed out of a relatively scant ring of matter, situated between
Mars and Jupiter and resembling in composition the immensely more
massive rings from which, according to Laplace's hypothesis, the
planets were born. It is held by the supporters of this theory that
the attraction of the giant Jupiter was sufficient to prevent the
small, nebulous ring that gave birth to the asteroids from condensing
like the others into a single planet.

But if we accept the explosion theory, with its corollary that minor
explosions followed the principal one, we have still an unanswered
question before us: What caused the explosions? The idea of a world
blowing up is too Titanic to be shocking; it rather amuses the
imagination than seriously impresses it; in a word, it seems
essentially chimerical. We can by no appeal to experience form a
mental picture of such an occurrence. Even the moon did not blow up
when it was wrecked by volcanoes. The explosive nebulæ and new stars
are far away in space, and suggest no connection with such a
catastrophe as the bursting of a planet into hundreds of pieces. We
cannot conceive of a great globe thousands of miles in diameter
resembling a pellet of gunpowder only awaiting the touch of a match to
cause its sudden disruption. Somehow the thought of human agency
obtrudes itself in connection with the word ``explosion,'' and we
smile at the idea that giant powder or nitro-glycerine could blow up a
planet. Yet it would only need enough of them to do it.

After all, we may deceive ourselves in thinking, as we are apt to do,
that explosive energies lock themselves up only in small masses of
matter. There are many causes producing explosions in nature, every