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Half-hours with the Telescope - Being a Popular Guide to the Use of the Telescope as a - Means of Amusement and Instruction. by Richard Anthony Proctor
page 91 of 115 (79%)

In transit the first satellite moves fastest, the fourth slowest, the
others in their order. The shadow moves just as fast (appreciably) as
the satellite it belongs to. Sometimes the shadow of the satellite may
be seen to overtake (apparently) the disc of another. In such a case the
shadow does not pass over the disc, but the disc conceals the shadow.
This is explained by the fact that the shadow, if visible throughout its
length, would be a line reaching slantwise from the satellite it belongs
to, and the end of the shadow (that is, the point where it meets the
disc) is _not_ the point where the shadow crosses the orbit of any inner
satellite. Thus the latter may be interposed between the end of the
shadow--the only part of the shadow really visible--and the eye; but the
end of the shadow _cannot_ be interposed between the satellite and the
eye. If a satellite _on the disc_ were eclipsed by another satellite,
the black spot thus formed would be in another place from the black spot
on the planet's body. I mention all this because, simple as the question
may seem, I have known careful observers to make mistakes on this
subject. A shadow is seen crossing the disc and overtaking, apparently,
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
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