These kept them quiet for a little while, but the books were soon finished, even when Bunny took Sue's and gave her his, to change about.
"You come back and sit in my seat, Bunny," Sue invited her brother after a while.
"No, you come with me," said Bunny. So Sue got in with him, but she wanted to sit next to the window, and as Bunny wanted that place himself, they were not satisfied, until Sue went back in her own seat.
About this time Bunny looked up and saw a long cord stretched overhead in the car, like a clothes line. It hung down from the car ceiling, and ran over little brass wheels, or pulleys, like those on Mr. Brown's boats, only much smaller.
"Do you see that cord, Sue?" asked Bunny.
"Yes," answered the little girl. "What's it for?"
"That's what holds the cars together," Bunny said. "The cars are tied to the engine with that cord."
Of course this was not so, for it takes strong iron chains and bars to hold the railroad cars one to another, and to the engine. But Bunny thought the cord, that blew a whistle in the engine, kept the train from coming apart.
"Is that what it's for?" asked Sue. "It isn't a very big string for to hold a train."
"Oh, it's very strong," Bunny said. "Nobody could break it."