can scarcely be accidental.

Professor Darwin's first researches on this subject were communicated to
the Royal Society, December 18, 1879. They were followed, January 20,
1881,[1178] by an inquiry on the same principles into the earlier
condition of the entire solar system. The results were a warning against
hasty generalisation. They showed that the lunar-terrestrial system, far
from being a pattern for their development, was a singular exception
among the bodies swayed by the sun. Its peculiarity resides in the fact
that the moon is _proportionately_ by far the most massive attendant
upon any known planet. Its disturbing power over its primary is thus
abnormally great, and tidal friction has, in consequence, played a
predominant part in bringing their mutual relations into their present
state.

The comparatively late birth of the moon tends to ratify this inference.
The dimensions of the earth did not differ (according to our present
authority) very greatly from what they now are when her solitary
offspring came, somehow, into existence. This is found not to have been
the case with any other of the planets. It is unlikely that the
satellites of Jupiter, Saturn, or Mars (we may safely add, of Uranus or
Neptune) ever revolved in much narrower orbits than those they now
traverse; it is practically certain that they did not, like our moon,
originate very near the _present_ surfaces of their primaries.[1179]
What follows? The tide-raising power of a body grows with vicinity in a
rapidly accelerated ratio. Lunar tides must then have been on an
enormous scale when the moon swung round at a fraction of its actual
distance from the earth. But no other satellite with which we are
acquainted occupied at any time a corresponding position. Hence no other
satellite ever possessed tide-raising capabilities in the least
comparable to those of the moon. We conclude once more that tidal
friction had an influence here very different from its influence
elsewhere. Quite possibly, however, that influence may be more nearly
spent than in less advanced combinations of revolving globes. Mr. Nolan
concluded in 1895[1180] that it still retains appreciable efficacy in
the several domains of the outer planets. The moons of Jupiter and
Saturn are, by his calculations, in course of sensible retreat, under
compulsion of the perennial ripples raised by them on the surfaces of
their gigantic primaries. He thus connects the interior position of the