Chain'd to one centre whirl'd the kindred spheres,
And mark'd with lunar cycles solar years.


[_When earth recoiling_. l. 84. On supposition that the moon was thrown
from the earth by the explosion of water or the generation of other
vapours of greater power, the remaining part of the globe would recede
from its orbit in one direction as the moon receded in another, and that
in proportion to the respective momentum of each, and would afterwards
revolve round their common centre of gravity.

If the moon rose from any part of the earth except exactly at the line
or poles, the shock would tend to turn the axis of the earth out of its
previous direction. And as a mass of matter rising from deep parts of
the globe would have previously acquired less diurnal velocity than the
earth's surface from whence it rose, it would receive during the time of
its rising additional velocity from the earth's surface, and would
consequently so much retard the motion of the earth round its axis.

When the earth thus receded the shock would overturn all its buildings
and forests, and the water would rush with inconceivable violence over
its surface towards the new satellite, from two causes, both by its not
at first acquiring the velocity with which the earth receded, and by the
attraction of the new moon, as it leaves the earth; on these accounts at
first there would be but one tide till the moon receded to a greater
distance, and the earth moving round a common centre of gravity between
them, the water on the side furthest from the moon would acquire a
centrifugal force in respect to this common centre between itself and
the moon.]