"They last six and seven weeks at a time," replied Mary, "so that Jupiter would scarcely be a comfortable world to live on yet. Besides, it is still in the fiery stage." "Won't you tell me some more about the little moons of Jupiter?" asked Harry. THE MOONS OF JUPITER. "They are not so little, after all, brother, except the first one, which is only one hundred miles wide. It is such a shy little moon that it keeps hiding behind Jupiter, or gets so close to him that it is lost in the glare of light from the giant planet. We had no idea it was there at all until an American astronomer, Professor Barnard, caught sight of it one evening. It was playing hide-and-seek as usual, but Professor Barnard, with his keen eyes, spied the little speck of light. It is now known as the fifth moon of Jupiter. It was only discovered in 1892, and just think, that for the hundreds and hundreds of years it has been there, yet no one had seen it. The French people were so delighted because Professor Barnard caught sight of the little truant that they gave him a beautiful gold medal." [Illustration: JUPITER AND HIS MOONS.] "Won't you show the little moon to me sometime?" said Harry. "I should like to see it so much." "You can only see it through a very large telescope; but I can show you the other four moons if Uncle Robert will lend us his telescope." "Here he comes," said Harry, in great glee, as he saw Uncle Robert crossing the meadow. "Won't you bring over your telescope this evening?" said Harry pleadingly, as he told him what Mary had just said. "Certainly, my little man," his uncle replied; "but we can only see three of the moons this evening as one of them is eclipsed." "What's that?" said Harry, in surprise at the strange word. "Eclipsed means hidden," said Mary, laughing. "If Uncle Robert stands right in front of you, as he is doing just now, he hides me from you, so I am eclipsed." "Very true," said Uncle Robert, laughing heartily at the hint. "Planet Mary is eclipsed by Uncle Robert, and poor little Planet Harry cannot see her till Uncle Robert gets out of the way." This he immediately proceeded to do, and next moment he was pursuing Fido, who was having a not over-friendly encounter with a strange cat in a neighbor's garden. "Oh, dear," said Harry, in distress, "where were we? We were up in the sky among the planets, and now Uncle Robert has brought us back again to earth. Do listen to poor Fido." He certainly seemed to be getting the worse of the encounter with Pussy; but when Uncle Robert came to the rescue the enemy vanished, and Fido, nothing daunted, went in search of other prey. When peace and quiet were once more restored, Mary resumed her story. ECLIPSE OF JUPITER'S MOONS.