here they were. They slowly formed and changed, and by moving all
together showed him that the sun rotated about once a month.

Before taking leave of Galileo's astronomical researches, I must
mention an observation made at the end of 1612, that the apparent
triplicity of Saturn (Fig. 46) had vanished.

[Illustration: FIG. 49.--A portion of the sun's disk as seen in a
powerful modern telescope.]

"Looking on Saturn within these few days, I found it solitary,
without the assistance of its accustomed stars, and in short
perfectly round and defined, like Jupiter, and such it still
remains. Now what can be said of so strange a metamorphosis? Are
perhaps the two smaller stars consumed like spots on the sun? Have
they suddenly vanished and fled? Or has Saturn devoured his own
children? Or was the appearance indeed fraud and illusion, with
which the glasses have so long time mocked me and so many others
who have so often observed with me? Now perhaps the time is come to
revive the withering hopes of those, who, guided by more profound
contemplations, have fathomed all the fallacies of the new
observations and recognized their impossibility! I cannot resolve
what to say in a chance so strange, so new, so unexpected. The
shortness of time, the unexampled occurrence, the weakness of my
intellect, the terror of being mistaken, have greatly confounded
me."

However, he plucked up courage, and conjectured that the two attendants
would reappear, by revolving round the planet.

[Illustration: FIG. 50.--Saturn and his rings, as seen under the most
favourable circumstances.]

The real reason of their disappearance is well known to us now. The
plane of Saturn's rings oscillates slowly about our line of sight, and
so we sometimes see them edgeways and sometimes with a moderate amount
of obliquity. The rings are so thin that, when turned precisely
edgeways, they become invisible. The two imaginary attendants were the
most conspicuous portions of the ring, subsequently called _ansae_.

I have thought it better not to interrupt this catalogue of brilliant
discoveries by any biographical details; but we must now retrace our
steps to the years 1609 and 1610, the era of the invention of the
telescope.

By this time Galileo had been eighteen years at Padua, and like many
another man in like case, was getting rather tired of continual
lecturing. Moreover, he