rbit round the earth.

There are astronomers who think that other cosmic bodies, besides our
moon, may have been formed in this way. Possibly it is true of some of
the double stars, but we will not return to that question. The further
story of the moon, as it is known to astronomers, may be given in a few
words. The rotational movement of the earth is becoming gradually slower
on account of tidal influence; our day, in fact, becomes an hour longer
every few million years. It can be shown that this had the effect of
increasing the speed, and therefore enlarging the orbit, of the moon,
as it revolved round the earth. As a result, the moon drew further and
further away from the earth until it reached its present position, about
240,000 miles away. At the same time the tidal influence of the earth
was lessening the rotational movement of the moon. This went on until
it turned on its axis in the same period in which it revolves round
the earth, and on this account it always presents the same face to the
earth.

Through what chapters of life the moon may have passed in the meantime
it is impossible to say. Its relatively small mass may have been unable
to keep the lighter gases at its surface, or its air and water may, as
some think, have been absorbed. It is to-day practically an airless and
waterless desert, alternating between the heat of its long day and the
intense cold of its long night. Careful observers, such as Professor
Pickering, think that it may still have a shallow layer of heavy gases
at its surface, and that this may permit the growth of some stunted
vegetation during the day. Certain changes of colour, which are observed
on its surface, have been interpreted in that sense. We can hardly
conceive any other kind of life on it. In the dark even the gases will
freeze on its surface, as there is no atmosphere to retain the heat.
Indeed, some students of the moon (Fauth, etc.) believe that it is an
unchanging desert of ice, bombarded by the projectiles of space.

An ingenious speculation as to the effect on the earth of this
dislodgment of 5,000,000,000 cubic miles of its substance is worth
noting. It supposes that the bed of the Pacific Ocean represents the
enormous gap torn in its side by the delivery of the moon. At each side
of this chasm the two continents, the Old World and the New, would
be left floating on their molten ocean; and some have even seen a
confirmation of this in the lines of crustal weakness