erture being that of
the great telescope of the Washington Observatory (the largest refractor
in the world).

He has noted in the first place that the interior edge of the outer
bright ring, which marks the outer limit of the great division, is
irregular, but whether the irregularity is permanent or not he does not
know. The great division itself is found not to be actually black, but,
as was long since noted by Captain Jacob, of the Madras Observatory, a
very dark brown, as though a few scattered satellites travelled along
this relatively vacant zone of the system. Mr. Trouvelot has further
noticed that the shadow of the planet upon the rings, and especially
upon the outer ring, changes continually in shape, a circumstance which
he attributes to irregularities in the surface of the rings. For my own
part, I should be disposed to attribute these changes in the shape of
the planet's shadow (noted by other observers also) to rapid changes in
the deep cloud-laden atmosphere of the planet. Passing on, however, to
less doubtful observations, we find that the whole system of rings has
presented a clouded and spotted aspect during the last four years. Mr.
Trouvelot specially describes this appearance as observed on the parts
of the ring outside the disc, called by astronomers the _ansae_ (because
of their resemblance to handles), and it would seem, therefore, that the
spotted and cloudy portions are seen only where the background on which
the rings are projected is black. This circumstance clearly suggests
that the darkness of these parts is due to the background, or, in other
words, that the sky is in reality seen through those parts of the
ring-system, just as the darkness of the slate-coloured interior ring is
attributed, on the satellite theory, to the background of sky visible
through the scattered flight of satellites forming the dark ring. The
matter composing the dark ring has been observed by Mr. Trouvelot to be
gathered in places into compact masses, which prevent the light of the
planet from being seen through those portions of the dark ring where the
matter is thus massed together. It is clear that such peculiarities
could not possibly present themselves in the case of a continuous solid
or fluid ring-system, whereas they would naturally occur in a ring
formed of multitudes of minute bodies travelling freely around the
planet.

The point next to be mentioned is still more decisive. When the dark
ring was carefull