Another five hours, and the
water would come tearing and driving over the country, applying its
furious waves and currents to the work of denudation, which would
proceed apace. These high tides of enormously distant past ages
constitute the denuding agent which the geologist required. They are
very ancient--more ancient than the Carboniferous period, for instance,
for no trees could stand the furious storms that must have been
prevalent at this time. It is doubtful whether any but the very lowest
forms of life then existed. It is the strata at the bottom of the
geological scale that are of the most portentous thickness, and the only
organism suspected in them is the doubtful _Eozoon Canadense_. Sir
Robert Ball believes, and several geologists agree with him, that the
mighty tides we are contemplating may have been coaeval with this ancient
Laurentian formation, and others of like nature with it.

But let us leave geology now, and trace the inverted progress of events
as we recede in imagination back through the geological era, beyond,
into the dim vista of the past, when the moon was still closer and
closer to the earth, and was revolving round it quicker and quicker,
before life or water existed on it, and when the rocks were still
molten.

Suppose the moon once touched the earth's surface, it is easy to
calculate, according to the principles of gravitation, and with a
reasonable estimate of its size as then expanded by heat, how fast it
must then have revolved round the earth, so as just to save itself from
falling in. It must have gone round once every three hours. The month
was only three hours long at this initial epoch.

Remember, however, the initial length of the day. We found that it was
just possible for the earth to rotate on its axis in three hours, and
that when it did so, something was liable to separate from it. Here we
find the moon in contact with it, and going round it in this same
three-hour period. Surely the two are connected. Surely the moon was a
part of the earth, and was separating from it.

That is the great discovery--the origin of the moon.

Once, long ages back, at date unknown, but believed to be certainly as
much as fifty million years ago, and quite possibly one hundred million,
there was no moon, only the earth as a molten globe, rapidly spinning on
its axis--spinning in about three hours. Gradually, by reason of some
disturbing causes, a protuberance, a sort of bud, forms at one si