,
a satellite in transit. It seems therefore, on a first view, that the
shadow will hide the satellite, and observers have even said that they
have _seen_ this happen. But they are deceived. It is obvious that _if
one satellite eclipse another, the shadows of both must occupy the same
point on Jupiter's body_. Thus it is the overtaking of one _shadow_ by
another on the disc, and not the overtaking of a _satellite_ by a
shadow, which determines the occurrence of that as yet unrecorded
phenomenon, the eclipse of one satellite by another.[13]

The satellites when far from Jupiter seem to lie in a straight line
through his centre. But as a matter of fact they do not in general lie
in an exact straight line. If their orbits could be seen as lines of
light, they would appear, in general, as very long ellipses. The orbit
of the fourth would frequently be seen to be _quite clear_ of Jupiter's
disc, and the orbit of the third might in some very exceptional
instances pass _just_ clear of the disc. The satellites move most nearly
in a straight line (apparently) when Jupiter comes to opposition in the
beginning of February or August, and they appear to depart most from
rectilinear motion when opposition occurs in the beginning of May and
November. At these epochs the fourth satellite may be seen to pass above
and below Jupiter's disc at a distance equal to about one-sixth of the
disc's radius.

The shadows do not travel in the same apparent paths as the satellites
themselves across the disc, but (in an inverting telescope) _below_ from
August to January, and _above_ from February to July.

We come now to the most charming telescopic object in the heavens--the
planet Saturn. Inferior only to Jupiter in mass and volume, this planet
surpasses him in the magnificence of his system. Seen in a telescope of
adequate power, Saturn is an object of surpassing loveliness. He must be
an unimaginative man who can see Saturn for the first time in such a
telescope, without a feeling of awe and amazement. If there is any
object in the heavens--I except not even the Sun--calculated to impress
one with a sense of the wisdom and omnipotence of the Creator it is
this. "His fashioning hand" is indeed visible throughout space, but in
Saturn's system it is most impressively manifest.

Saturn, to be satisfactorily seen, requires a much more powerful
telescope than Jupiter. A good 2-inch telescope will do much, however,
in exhibiting his rings and belt