h revolve around him. We
see, nearer home, how the moon revolves around the earth. We see how all
the planetary system revolves around the sun. All these considerations
were present to Huyghens when he came to the conclusion that, whether
the curious appendages were actually attached to the planet or were
physically free from it, they must still be in rotation.

Provided with such reasonings, it soon became easy to conjecture the
true nature of the Saturnian system. We have seen how the appendages
declined to invisibility once every fifteen years, and then gradually
reappeared in the form, at first, of rectilinear arms projecting
outwards from the planet. The progressive development is a slow one, and
for weeks and months, night after night, the same appearance is
presented with but little change. But all this time both Saturn and the
mysterious objects around him are rotating. Whatever these may be, they
present the same appearance to the eye, notwithstanding their ceaseless
motion of rotation.

What must be the shape of an object which satisfies the conditions here
implied? It will obviously not suffice to regard the projections as two
spokes diverging from the planet. They would change from visibility to
invisibility in every rotation, and thus there would be ceaseless
alterations of the appearance instead of that slow and gradual change
which requires fifteen years for a complete period. There are, indeed,
other considerations which preclude the possibility of the objects being
anything of this character, for they are always of the same length as
compared with the diameter of the planet. A little reflection will show
that one supposition--and indeed only one--will meet all the facts of
the case. If there were a thin symmetrical ring rotating in its own
plane around the equator of Saturn, then the persistence of the object
from night to night would be accounted for. This at once removes the
greater part of the difficulty. For the rest, it was only necessary to
suppose that the ring was so thin that when turned actually edgewise to
the earth it became invisible, and then as the illuminated side of the
plane became turned more and more towards the earth the appendages to
the planet gradually increased. The handle-shaped appearance which the
object periodically assumed demonstrated that the ring could not be
attached to the globe.

At length Huyghens found that he had the clue to the great enigma which
had perplexed