"What's the surprise, Uncle Billy?" asked Beth. "Why are you stopping?"
"I don't know myself," said Uncle Billy with a frown on his forehead, as the car gradually came to a stop, "but I'll have to find out."
"Whatever's the matter?" cried Jerry. "Do you think we're having engine trouble?" and she hopped out and stood by the roadside gazing at the car.
"Nothing so easy as that," answered Uncle Billy, in great disgust; "it's gas. We have run out of it. Looks as though they didn't fill up the tank in the garage before we started, as I told them to do."
"Gasoline!" gasped Beth, "and that's what makes it go."