', p. 47 and 263; Arago, in the 'Annuaire', 1842, p. 412). It is a
renewal of Kepler's views.
Considering the narrow limitation of the Sun's atmosphere, which we have
just described, we may with much probability regard the existence of a very
compressed annulus of nebulous matter,* revolving freely in space between
the orbits of Venus and Mars, as the material cause of the zodiacal light.
[footnote] *Cominicus Cassini was the first to assume, as did subsequently
Laplace, Schubert, and Poisson, the hypothesis of a separate ring to explain
the form of the zodiacal light. He says distinctly, "If the orbits of
Mercury and Venus were visible (throughout their whole extent), we should
invariably observe them with the same figure and in the same position with
regard to the Sun, and at the same time of the year with the zodiacal
light." ('M??m. de l'Acad.', t. viii., 1730, p. 218, and Biot, in the
'Comptes Rendus', 1836, t. iii., p. 666.) Cassini believed that the
nebulous ring of zodiacal light consisted of innumerable small planetary
bodies revolving round the Sun. He even went so far as to believe that the
fall of fire-balls might be connected with the passage of the Earth through
the zodiacal nebulous ring. Olmsted, and especially Biot (op.
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