Jim, with his father, goes to see his grandfather. In the train Jim often puts his head out of the window. His father says, “Jim! Don’t put your head out of the window!” But Jim goes on putting his head out of the window.    
    Here his father takes Jim’s cap quietly, hides it behind his back and says, “You see your cap is gone.” Jim is afraid.
    His father says, “Well, whistle（吹口哨）once. Perhaps your cap will come back.” Jim whistles. His father puts quickly the cap on Jim’s head.
    Oh! It’s wonderful! Jim laughs. He quickly takes his father’s cap and throws it out of the window. “Now it’s your turn to whistle, Dad!” He says happily.