s. I have never seen him satisfactorily
myself with such an aperture, but Mr. Grover has not only seen the
above-named features, but even a penumbra to the shadow on the rings
with a 2-inch telescope.

Saturn revolving round the sun in a long period--nearly thirty
years--presents slowly varying changes of appearance (see Plate 7). At
one time the edge of his ring is turned nearly towards the earth; seven
or eight years later his rings are as much open as they can ever be;
then they gradually close up during a corresponding interval; open out
again, exhibiting a different face; and finally close up as first seen.
The last epoch of greatest opening occurred in 1856, the next occurs in
1870: the last epoch of disappearance occurred in 1862-63, the next
occurs in 1879. The successive views obtained are as in Plate 7 in order
from right to left, then back to the right-hand figure (but sloped the
other way); inverting the page we have this figure thus sloped, and the
following changes are now indicated by the other figures in order back
to the first (but sloped the other way and still inverted), thus
returning to the right-hand figure as seen without inversion.

The division in the ring can be seen in a good 2-inch aperture in
favourable weather. The dark ring requires a good 4-inch and good
weather.

Saturn's satellites do not, like Jupiter's, form a system of nearly
equal bodies. Titan, the sixth, is probably larger than any of
Jupiter's satellites. The eighth also (Japetus) is a large body,
probably at least equal to Jupiter's third satellite. But Rhea, Dione,
and Tethys are much less conspicuous, and the other three cannot be seen
without more powerful telescopes than those we are here dealing with.

So far as my own experience goes, I consider that the five larger
satellites may be seen distinctly in good weather with a good 3-1/2-inch
aperture. I have never seen them with such an aperture, but I judge from
the distinctness with which these satellites may be seen with a 4-inch
aperture. Titan is generally to be looked for at a considerable distance
from Saturn--_always_ when the ring is widely open. Japetus is to be
looked for yet farther from the disc. In fact, when Saturn comes to
opposition in perihelion (in winter only this can happen) Japetus may be
as far from Saturn as one-third of the apparent diameter of the moon. I
believe that under these circumstances, or even under less favourable
circumstances, Japetus