ll known celestial bodies, through being girt around its
equator by what looks like a broad, flat ring of exceeding thinness.
This, however, upon closer examination, is found to be actually composed
of three concentric rings. The outermost of these is nearly of the same
brightness as the body of the planet itself. The ring which comes
immediately within it is also bright, and is separated from the outer
one all the way round by a relatively narrow space, known as "Cassini's
division," because it was discovered by the celebrated French
astronomer, J.D. Cassini, in the year 1675. Inside the second ring, and
merging insensibly into it, is a third one, known as the "crape ring,"
because it is darker in hue than the others and partly transparent, the
body of Saturn being visible through it. The inner boundary of this
third and last ring does not adjoin the planet, but is everywhere
separated from it by a definite space. This ring was discovered
_independently_[23] in 1850 by Bond in America and Dawes in England.

[Illustration: PLATE XV. THE PLANET SATURN

From a drawing made by Professor Barnard with the Great Lick Telescope.
The black band fringing the outer ring, where it crosses the disc, is
portion of the _shadow which the rings cast upon the planet_. The black
wedge-shaped mark, where the rings disappear behind the disc at the
left-hand side, is portion of the _shadow which the planet casts upon
the rings_.

(Page 237)]

As distinguished from the crape ring, the bright rings must have a
considerable closeness of texture; for the shadow of the planet may be
seen projected upon them, and their shadows in turn projected upon the
surface of the planet (see Plate XV., p. 236).

According to Professor Barnard, the entire breadth of the ring system,
that is to say, from one side to the other of the outer ring, is 172,310
miles, or somewhat more than double the planet's diameter.

In the varying views which we get of Saturn, the system of the rings is
presented to us at very different angles. Sometimes we are enabled to
gaze upon its broad expanse; at other times, however, its thin edge is
turned exactly towards us, an occurrence which takes place after
intervals of about fifteen years. When this happened in 1892 the rings
are said to have disappeared entirely from view in the great Lick
telescope. We thus get an idea of their small degree of thickness, which
would appear to be only about 50 miles. The last time the syst