"That's what you meant when you said the river worked," said Frank. "Did these boulders come down the river too?"
"The story of the boulders," said Uncle Robert, "is different from the story of the pebbles. The water helped grind the pebbles, but it took ice to make the boulders."
"Ice!" the children all exclaimed.
"Yes, ice. A long, long while ago this land was covered by a great river, or sea of ice, and that was the time these boulders were made," said Uncle Robert.
"Can we read about that in the Big Book?" asked Donald.
"Some of it," said Uncle Robert. "There are many wonderful stories in this beautiful world—stories more wonderful than any fairy tale. But we must go home now, children; it's getting late."
The setting sun threw long shadows of the trees over the river as they rowed home, and the happy day was done.
CHAPTER XIII.
A RAINY DAY.
It was raining, but no one was surprised. They had expected it.