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, he would not look upon her, lest he, too, be turned to stone; but, guided by the reflection in the buckler, smote off her head, carried it high over Libya, the dropping blood turning to serpents, which have infested those deserts ever since.

[Illustration:  Fig. 67.—­Circumpolar Constellations.  Always visible.  In this position.—­January 20th, at 10 o’clock; February 4th, at 9 o’clock; and February 19th, at 8 o’clock.]

The human mind has always been ready to deify and throne in the skies the heroes that labor for others.  Both Perseus and Hercules are divine by one parent, and human by the other.  They go up and down the earth, giving deliverance to captives, and breaking every yoke.  They also seek to purge away all evil; they slay dragons, gorgons, devouring monsters, cleanse the foul places of earth, and one of them so wrestles with death as to win a victim from his grasp.  Finally, by [Page 201] an ascension in light, they go up to be in light forever.  They are not ideally perfect.  They right wrong by