The two
discs were perfectly rounded and separately discernible until they
touched. Moreover, I was able to distinguish upon one of the darker
bands the disc of the satellite itself, while upon a lighter band its
round black shadow was at the same time perfectly defined. This
wonderfully clear presentation of one of the most interesting of
astronomical phenomena so absorbed my attention that I watched the
satellite and shadow during their whole course, though the former,
passing after a time on to a light band, became comparatively
indistinct. The moment, however, that the outer edge passed off the
disc of Jupiter, its outline became perfectly visible against the
black background of sky. What was still more novel was the occultation
for some little time of a star, apparently of the tenth magnitude, not
by the planet but by the satellite, almost immediately after it passed
off the disc of the former. Whether the star actually disappeared at
once, as if instantaneously extinguished, or whether, as I thought at
the moment, it remained for some tenth of a second partially visible,
as if refracted by an atmosphere belonging to the satellite, I will
not venture to say.
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