One morning mother said, "Polly, will you go to the store for me? I need a can of corn. We must have it for dinner."

"May Peter go, too, mother?"

"Oh, yes, Peter may go, if he wishes. Run and find him."

Now Polly and Peter liked to go to the store. It belonged to their father. Sometimes they helped him unpack goods. Sometimes they sat still and watched the customers.

Sometimes he let them play keeping store. Once Polly had really sold some candy to another little girl.

But to-day they could not stay to play. They must get the can of corn for mother, and come home.

They went down the hill. At the railroad tracks they stopped. They looked for a train. They saw none, so they ran across the tracks.

Then they came to the bridge. You can find it on the map in the front of this book.

They stopped to look over the rail at the water, far below.

"O Polly!" said Peter. "What is on the water?"

"Why, it is ice, Peter. The top of the water is frozen. See, the ice goes nearly across the river."

"Ice, ice!" shouted Peter. "Now winter is almost here. The leaves have gone. The ice has come. Let's run and tell father."

The children ran to the store.

"Father, father," called Peter, "we have seen ice!"

"So have I," said father. "Where did you see it?"

"We saw it from the bridge. The river is frozen at the sides. It is not frozen in the middle."

"Yes," said father. "It freezes first at the edges, because the water flows more slowly there. In the middle it flows faster.

"Every cold night that ice will grow. It will soon cover the middle of the river, too. And at the same time it will grow thicker."

"By and by it will be so thick that we can walk upon it. Then it is time to learn to skate. Perhaps you can learn this winter."

"When the ice is thick enough, men cut it into blocks. What will they do with them?"

"Make houses of them," said Peter.

"O Peter, we are not Eskimos," said Polly. "I know, father. They will put the ice into big ice houses. They will keep it to use in the hot summer. I saw them doing it last winter."

"Right, Polly. That is where our ice comes from in the summer."

"Does all the water in the river freeze, father? Where do the fishes go? Are they in the ice?"

"The ice is lighter than the water, Peter. So it stays on top of the water. The bottom of our river does not freeze. The fishes are there. They do not mind the cold as we do.

"Did you come to the store just to tell me about the ice, chicks?"

"No, father," said Polly. "We came for a can of corn. We saw the ice when we were on the bridge."

"Then here is the corn. Take it to mother and tell her about the ice."

Off went the children. When they came to the bridge, Peter dropped some small stones on the ice. But it did not break.

"It must be thick now, Polly," said he. "I wish we could skate."

"We weigh more than those stones do, Peter. I think the cold will have to make the ice grow more before father will let us. And, anyway, we have no skates."

"Let's tell mother about that, too, Polly. Perhaps she knows where there are some."

So Peter and Polly hurried up the hill to find their mother.