corresponding data for the shadows.

The eclipses of the satellites in Jupiter's shadow, and their
occultations by his disc, are also given in 'Dietrichsen's Almanac.'

In the inverting telescope the satellites move from right to left in the
nearer parts of their orbit, and therefore transit Jupiter's disc in
that direction, and from left to right in the farther parts. Also note
that _before_ opposition, (i.) the shadows travel in front of the
satellites in transiting the disc; (ii.) the satellites are eclipsed in
Jupiter's _shadow_; (iii.) they reappear from behind his _disc_. On the
other hand, _after_ opposition, (i.) the shadows travel _behind_ the
satellites in transiting the disc; (ii.) the satellites are occulted by
the _disc_; (iii.) they reappear from eclipse in Jupiter's _shadow_.

Conjunctions of the satellites are common phenomena, and may be waited
for by the observer who sees the chance. An eclipse of one satellite by
the shadow of another is not a common phenomenon; in fact, I have never
heard of such an eclipse being seen. That a satellite should be quite
extinguished by another's shadow is a phenomenon not absolutely
impossible, but which cannot happen save at long intervals.

The shadows are not _black spots_ as is erroneously stated in nearly all
popular works on astronomy. The shadow of the fourth, for instance, is
nearly all penumbra, the really black part being quite minute by
comparison. The shadow of the third has a considerable penumbra, and
even that of the first is not wholly black. These penumbras may not be
perceptible, but they affect the appearance of the shadows. For
instance, the shadow of the fourth is perceptibly larger but less black
than that of the third, though the third is the larger satellite.