summer. It will also be seen that
the side of the ring towards this half of the ball is now in the light,
so that a small insect on this half of the ball would see the bright
side of the ring. A Saturnian correspondingly placed would get reflected
sunlight from the ring system _both by day and by night_. Moving the
ball and ring so that the shadow returns to its first position, an
entire Saturnian year will have been illustrated. These changes can be
still better shown with a Saturnian orrery (see plate viii. of my
Saturn), which can be very easily constructed.

[31] Not 'of course' because Tycho used it, for, like other able
students of science, he made mistakes from time to time. Thus he argued
that the earth cannot rotate on her axis, because if she did bodies
raised above her surface would be left behind--an argument which even
the mechanical knowledge of his own time should have sufficed to
invalidate, though it is still used from time to time by paradoxers of
our own day.

[32] Chinese chronicles contain other references to new stars. The
annals of Ma-touan-lin, which contain the official records of remarkable
appearances in the heavens, include some phenomena which manifestly
belong to this class. Thus they record that in the year 173 a star
appeared between the stars which mark the hind feet of the Centaur. This
star remained visible from December in that year until July in the next
(about the same time as Tycho Brahe's and Kepler's new stars, presently
to be described). Another star, assigned by these annals to the year
1011, seems to be the same as a star referred to by Hepidannus as
appearing A.D. 1012. It was of extraordinary brilliancy, and remained
visible in the southern part of the heavens during three months. The
annals of Ma-touan-lin assign to it a position low down in Sagittarius.

[33] Still a circumstance must be mentioned which tends to show that the
star may have been visible a few hours earlier than Dr. Schmidt
supposed. Mr. M. Walter, surgeon of the 4th regiment, then stationed in
North India, wrote (oddly enough, on May 12, 1867, the first anniversary
of Mr. Birmingham's discovery) as follows to Mr. Stone:--'I am certain
that this same conflagration was distinctly perceptible here at least
six hours earlier. My knowledge of the fact came about in this wise. The
night of the 12th of May last year was exceedingly sultry, and about
eight o'clock on that evening I got up from the tea-table and r