l movement of rotation in the direction west to east. As it cooled
it could not fail to experience a gradual condensation, and in
consequence to rotate with greater and greater rapidity. If the nebulous
matter extended originally in the plane of its equator, as far as the
limit where the centrifugal force exactly counterbalanced the attraction
of the nucleus, the molecules situate at this limit ought, during the
process of condensation, to separate from the rest of the atmospheric
matter and to form an equatorial zone, a ring, revolving separately and
with its primitive velocity. We may conceive that analogous separations
were effected in the remoter strata of the nebula at different epochs
and at different distances from the nucleus, and that they gave rise to
a succession of distinct rings, all lying in nearly the same plane, and
all endowed with different velocities.

This being once admitted, it is easy to see that the permanent stability
of the rings would have required a regularity of structure throughout
their whole contour, which is very improbable. Each of them,
accordingly, broke in its turn into several masses, which were obviously
endowed with a movement of rotation coinciding in direction with the
common movement of revolution, and which, in consequence of their
fluidity, assumed spheroidal forms. In order, next, that one of those
spheroids may absorb all the others belonging to the same ring, it is
sufficient to suppose it to have a mass greater than that of any other
spheroid of its group.

Each of the planets, while in this vaporous condition to which we have
just alluded, would manifestly have a central nucleus, gradually
increasing in magnitude and mass, and an atmosphere offering, at its
successive limits, phenomena entirely similar to those which the solar
atmosphere, properly so called, had exhibited. We are here
contemplating the birth of satellites and the birth of the ring
of Saturn.

The Nebular Hypothesis, of which I have just given an imperfect sketch,
has for its object to show how a nebula endowed with a general movement
of rotation must eventually transform itself into a very luminous
central nucleus (a sun), and into a series of distinct spheroidal
planets, situate at considerable distances from one another, all
revolving around the central sun, in the direction of the original
movement of the nebula; how these planets ought also to have movements
of rotation in similar directions; how,