ame time
that the gravitative force in Jupiter is more than twice as great as in
Saturn, his velocity of rotation is very little greater, so that the
opposition of the centrifugal force to the centripetal is not much more
than half.

But now, not judging more than roughly of the effects of these several
factors, co-operating in various ways and degrees, some to aid
concentration and others to resist it, it is sufficiently manifest that,
other things equal, the larger nebulous spheroids, longer in losing
their heat, will more slowly reach high specific gravities; and that
where the contrasts in size are so immense as those between the greater
and the smaller planets, the smaller may have reached relatively high
specific gravities when the greater have reached but relatively low
ones. Further, it appears that such qualification of the process as
results from the more rapid genesis of heat in the larger masses, will
be countervailed where high velocity of rotation greatly impedes the
circulating currents. Thus interpreted then, the various specific
gravities of the planets may be held to furnish further evidences
supporting the Nebular Hypothesis.

* * * * *

Increase of density and escape of heat are correlated phenomena, and
hence in the foregoing section, treating of the respective densities of
the celestial bodies in connexion with nebular condensation, much has
been said and implied respecting the accompanying genesis and
dissipation of heat. Quite apart, however, from the foregoing arguments
and inferences, there is to be noted the fact that in the present
temperatures of the celestial bodies at large we find additional
supports to the hypothesis; and these, too, of the most substantial
character. For if, as is implied above, heat must inevitably be
generated by the aggregation of diffused matter, we ought to find in all
the heavenly bodies, either present high temperatures or marks of past
high temperatures. This we do, in the places and in the degrees which
the hypothesis requires.

Observations showing that as we descend below the Earth's surface there
is a progressive increase of heat, joined with the conspicuous evidence
furnished by volcanoes, necessitate the conclusion that the temperature
is very high at great depths. Whether, as some believe, the interior of
the Earth is still molten, or whether, as Sir William Thomson contends,
it must be solid; there is agreement in the