her minor
planets) as a possible source of the meteorites. Firstly, that
notwithstanding the small mass of the planet a very powerful volcano
would still be required; and secondly, that we are obliged to assume
that for every one which ever reached the earth at least 50,000 must
have been ejected. It is thus plain that if the meteorites have really
been driven from some planet of the solar system, large or small, the
volcano must, from one cause or another, have been a very powerful one.
We are thus led to enquire which planet possesses on other grounds the
greatest probability in its favour.

We admit of course that at the present time the volcanoes on the earth
are utterly devoid of the necessary power; but were the terrestrial
volcanoes always so feeble as they are in these later days? Grounds are
not wanting for the belief that in the very early days of geological
time the volcanic energy on the earth was much greater than at present.
We admit fully the difficulties of the view that the meteorites have
really come from the earth; but they must have some origin, and it is
reasonable to indicate the source which seems to have most probability
in its favour. Grant for a moment that in the primaeval days of volcanic
activity there were some mighty throes which hurled forth missiles with
the adequate velocity: these missiles would ascend, they would pass from
the gravitation of the earth, they would be seized by the gravitation of
the sun, and they would be compelled to revolve around the sun for ever
after. No doubt the resistance of the air would be a very great
difficulty, but this resistance would be greatly lessened were the
crater at a very high elevation above the sea level, while, if a vast
volume of ejected gases or vapours accompanied the more solid material,
the effect of the resistance of the air would be still further reduced.
Some of these objects might perhaps revolve in hyperbolic orbits, and
retreat never to return; while others would be driven into elliptic
paths. Round the sun these objects would revolve for ages, but at each
revolution--and here is the important point--they would traverse the
point from which they were originally launched. In other words, every
object so projected from the earth would at each revolution cross the
track of the earth. We have in this fact an enormous probability in
favour of the earth as contrasted with Ceres. Only one Ceres-ejected
meteorite out of every 50,000 would p