art
of a circle near the north star as large as the earth's orbit, that
is, 185,000,000 miles in diameter. But, as already shown, that
circle is too small to be discernible at our distance. The wide
circle of the pole through the ages is really made up of the
interlaced curves of the annual curves continued through 25,870
years. The stem of the spinning top wavers, describes a circle, and
finally falls; the axis of the spinning earth wavers, describes a
circle of nearly 28,000 years, and never falls.

The star g Draconis, also called Etanin, is famous in modern astronomy,
because observations on this star led to the discovery of the
_aberration of light_. If we held a glass tube perpendicularly out
of the window of a car at rest, when the rain was falling straight
down, we could see the drops pass directly through. Put the car
in motion, and the drops would seem to start toward us, and the
top of the tube must be bent forward, or the drops entering would
strike on the backside of the tube carried toward them. So our
telescopes are bent forward on the moving earth, to enable the
entered light to reach the eye-piece. Hence the star does not appear
just where it is. As the earth moves faster in some parts of its
orbit than others, this aberration is sometimes greater than at
others. It is fortunate that light moves with a uniform velocity,
or this difficult, problem would be still further complicated.
The displacement of a star from this course is about 20".43.

[Page 200]
On the side of Polaris, opposite to Ursa Major, is King Cepheus,
made of a few dim stars in the form of the letter K. Near by is
his brilliant wife Cassiopeia, sitting on her throne of state.
They were the graceless parents who chained their daughter to a
rock for the sea-monster to devour; but Perseus, swift with the
winged sandals of Mercury, terrible with his avenging sword, and
invincible with the severed head of Medusa, whose horrid aspect of
snaky hair and scaly body turned to stone every beholder, rescues
the maiden from chains, and leads her away by the bands of love.
Nothing could be more poetical than the life of Perseus. When he
went to destroy the dreadful Gorgon, Medusa, Pluto lent him his
helmet, which would make him invisible at will; Minerva loaned
her buckler, impenetrable, and polished like a mirror; Mercury
gave him a dagger of diamonds, and his winged sandals, which would
carry him through the air. Coming to the loathsome thing, h