[footnote] * "If there should be molecules in the zones diffused by the
atmosphere of the Sun of too volatile a nature either to combine with one
another or with the planets, we must suppose that they would, in circling
round that luminary, present all the appearances of zodiacal light, without
opposing any appreciable resistance to the different bodies composing the
planetary system, either owing to their extreme rarity, or to the similarity
existing between their motion and that of the planets with which they come
in contact." -- Laplace, 'Expos. du Syst. du Monde' (ed. 5), p. 415.
When we consider the complication of variously-formed bodies which revolve
round the Sun in orbits of such dissimilar eccentricity--although we may not
be disposed, with the immortal author of the 'Mecanique Celeste', to regard
the largr number of comets as nebulous stars, passing from one central
system to another,* we yet can not fail to acknowledge that the planetary
system, especially so called (that is, the group of heavenly bodies which,
together with their satellites, revolve with but slightly eccentric orbits
round the Sun), constitutes but a small portion of the whole system with
respect to individual numbers, if not to mass.
[footnote] *Laplace, 'Exp.
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