impossible, especially
when it is considered that nebulous materials were in question.

The reform proposed by M. Faye consists in admitting that all the
planets inside Uranus are of pre-solar origin--that they took globular
form in the bosom of a nearly homogeneous nebula, revolving in a single
period, with motion accelerated from centre to circumference, and hence
agglomerating into masses with a direct rotation. Uranus and Neptune owe
their exceptional characteristics to their later birth. When they came
into existence, the development of the sun was already far advanced,
central force had acquired virtually its present strength, unity of
period had been abolished by its predominance, and motion was retarded
outward.

Thus, what we may call the relative chronology of the solar system is
thrown once more into confusion. The order of seniority of the planets
is now no easier to determine than the "Who first, who last?" among the
victims of Hector's spear. For M. Faye's arrangements, notwithstanding
the skill with which he has presented them, cannot be unreservedly
accepted. The objections to them, thoughtfully urged by M. C. Wolf[1170]
and Professor Darwin,[1171] are grave. Not the least so is his omission
to take account of an agency of change presently to be noticed.

A further valuable discussion of the matter was published by M. du
Ligondes in 1897.[1172] His views are those of Faye, modified to disarm
the criticisms they had encountered; and special attention may be
claimed for his weighty remark that each planet has a life-history of
its own, essentially distinct from those of the others, and, despite
original unity, not to be confounded with them. The drift of recent
investigations seems, indeed, to be to find the embryonic solar system
already potentially complete in the parent nebula, like the oak in an
acorn, and to relegate detailed explanations of its peculiarities to the
dim pre-nebular fore-time.

We now come to a most remarkable investigation--one, indeed, unique in
its profession to lead us back with mathematical certainty towards the
origin of a heavenly body. We refer to Professor Darwin's inquiries into
the former relations of the earth and moon.[1173]

They deal exclusively with the effects of tidal friction, and primarily
with those resulting, not from oceanic, but from "bodily" tides, such as
the sun and moon must have raised in past ages on a liquid or viscous
earth. The immediate effect of