Then he told them of the curious variable, or "winking" stars, which turn bright and faint alternately on a regular schedule, so many hours bright, and so many hours faint. Also he described the beauty of the planet _Jupiter_, surrounded by its four little moons, all of which could be seen with a small telescope. Then the children began to feel more cheerful, for they saw that being introduced to the creatures and people of Skyland was only the beginning of the study of astronomy. "So," finished Uncle Henry, "we don't need to feel that there is no more fun coming, for there are lots more faint constellations which are all beautiful, even though not plain enough for us to find easily in the beginning. Besides, if you ever journey to the South, beyond the earth's equator, you will find a whole new sky full of marvelous people, and creatures, and objects--all pictured in the flashing southern heavens." "Well," said Peter briskly, "what do we find to-night, Uncle Hen?" "We'll begin," replied Uncle Henry, "with a person you may have heard of--_Perseus_, who killed the terrible Gorgon _Medusa_." "Oh, I know him," cried Paul, "we read all 'bout him last year." "Quite right," said Uncle Henry, "then you remember that when he had killed _Medusa_, and cut off her head with his sword, he had to hold the head with the terrible face away from him, because everybody who looked at that face was instantly turned to stone." "Yes, yes, we know!" chorused the Society. "Well, now we'll find _Perseus_, his sword, and the head of _Medusa_," promised Uncle Henry. "All you have to do is to extend the line of _Andromeda's_ left leg and prolong it from her foot, straight out for about her whole length. (30) There you will find _Algenib_, the brightest star in _Perseus_. It is right in his neck, between his shoulders. From _Algenib_ you can trace a row of stars downward, almost to the _Pleiades_ in the bull's shoulder. This row of stars is _Perseus'_ body and legs. Then find two stars above _Algenib_, one over the other, and you have his head and helmet. "After that it is easy to start at _Algenib_ and trace out his right arm, with the sword. A line drawn toward _Perseus_ through the stars in _Andromeda's_ head and left hip points out the star _Algol_, which is the head of _Medusa_, held in _Perseus'_ left hand. (31) _Algol_ is a famous variable star, which the ancients named 'the dragon of the slowly winking eye.'" The children soon found all of _Perseus_, and all took part in drawing his skeleton on the blackboard. Then they watched _Algol_ in the sky, and expected to see it wink, until Uncle Henry told them that the wink is so slow that it takes seven hours for _Algol_ to become faint and bright again, and that then two and three-quarter days pass before _Algol_ winks again. This being the case the Society decided not to wait, and finished _Perseus_ up so that he looked this way: [Illustration]