is removed; and if we grant an explosion at
all, there seems to be nothing improbable in the hypothesis that the
fragments formed by the bursting of the parent mass would carry away
within themselves the same forces and reactions which caused the
original bursting, so that they themselves would be likely enough to
explode at some time in their later history."[8]

[Footnote 8: General Astronomy, by Charles A. Young. Revised edition,
1898, p. 372.]

The rival theory of the origin of the asteroids is that which assumes
that the planetary ring originally left off from the contracting solar
nebula between the orbits of Mars and Jupiter was so violently perturbed
by the attraction of the latter planet that, instead of being shaped
into a single globe, it was broken up into many fragments. Either
hypothesis presents an attractive picture; but that which presupposes
the bursting asunder of a large planet, which might at least have borne
the germs of life, and the subsequent shattering of its parts into
smaller fragments, like the secondary explosions of the pieces of a
pyrotechnic bomb, certainly is by far the more impressive in its appeal
to the imagination, and would seem to offer excellent material for some
of the extra-terrestrial romances now so popular. It is a startling
thought that a world can possibly carry within itself, like a dynamite
cartridge, the means of its own disruption; but the idea does not appear
so extremely improbable when we recall the evidence of collisions or
explosions, happening on a tremendous scale, in the case of new or
temporary stars.[9]

[Footnote 9: "Since the discovery of Eros, the extraordinary position of
its orbit has led to the suggestion that possibly Mars itself, instead
of being regarded as primarily a major planet, belonging to the
terrestrial group, ought rather to be considered as the greatest of the
asteroids, and a part of the original body from which the asteroidal
system was formed."--J. Bauschinger, Astronomische Nachrichten, No.
3542.]

Coming to the question of life upon the asteroids, it seems clear that
they must be excluded from the list of habitable worlds, whatever we
may choose to think of the possible habitability of the original planet
through whose destruction they may have come into existence. The largest
of them possesses a force of gravity far too slight to enable it to
retain any of the gases or vapors that are recognized as constituting an
atmosphere. But