"Quite sure, my little brother," she said, kissing him tenderly; "for hundreds and hundreds of years must pass away before anyone will have any idea that the earth is growing old."
"And what will become of the poor little fishes when the oceans dry up?" asked Nellie sadly, as she clasped her dollie closely in her arms, as though to protect it from the coming trouble.
"I expect they will all die," said Harry wisely; "because you know, Nellie, they can't live out of water. Can they?"
"Or else that fish Uncle Robert caught would have lived," said Nellie. "But please tell us a story about Mercury, Cousin Mary, and the other little planets."
"Well, Mercury is a very little planet, and instead of taking a year of three hundred and sixty-five days, it goes around the sun in eighty-eight days. That is, it goes round the sun four times while we go round it only once. Some think Mercury always keeps the same side turned to the sun, so that it is always day on one side and night on the other, but we are not quite sure about this yet."
"I should like to live on Mercury, wouldn't you, Harry?" said Nellie, clapping her hands with glee. "Just think of day all the time, and never having to go to sleep!"
"But you would get very tired of that," said Mary, "and long for the night to come. And, besides, would you not miss seeing the moon and the beautiful stars?"
"I would live on the edge of Mercury," said Harry thoughtfully, "so that when I was tired of day I might slip around it and have night. It must be very cold on the other side, where the sun does not shine, if Mercury gets all its heat from the sun."
"I suspect it is," said Mary, "and I don't believe we should like to live on Mercury, after all; so let us try the next planet, which is called Venus."