rmost planets.
At successive stages of the concentration, rings after the manner of
those of Saturn separated from the disklike mass, each breaking up and
consolidating into a body of nebulous matter which followed in the
same path, generally forming rings which became by the same process
the moons or satellites of the sphere. In this way the sun produced
eight planets which are known, and possibly others of small size on
the outer verge of the system which have eluded discovery. According
to this view, the planetary masses were born in succession, the
farthest away being the oldest. It is, however, held by an able
authority that the mass of the solar system would first form a rather
flat disk, the several rings forming and breaking into planets at
about the same time. The conditions in Saturn, where the inner ring
remains parted, favours the view just stated.

Before making a brief statement of the several planets, the asteroids,
and the satellites, it will be well to consider in a general way the
motions of these bodies about their centres and about the sun. The
most characteristic and invariable of these movements is that by which
each of the planetary spheres, as well as the satellites, describes an
orbit around the gravitative centre which has the most influence upon
it--the sun. To conceive the nature of this movement, it will be well
to imagine a single planet revolving around the sun, each of these
bodies being perfect spheres, and the two the only members of the
solar system. In this condition the attraction of the two bodies would
cause them to circle around a common centre of gravity, which, if the
planet were not larger or the sun smaller than is the case in our
solar system, would lie within the mass of the sun. In proportion as
the two bodies might approach each other in size, the centre of
gravity would come the nearer to the middle point in a line connecting
the two spheres. In this condition of a sun with a single planet,
whatever were the relative size of sun and planet, the orbits which
they traverse would be circular. In this state of affairs it should be
noted that each of the two bodies would have its plane of rotation
permanently in the same position. Even if the spheres were more or
less flattened about the poles of their axes, as is the case with all
the planets which we have been able carefully to measure, as well as
with the sun, provided the axes of rotation were precisely parallel to
each o