"They must be running without power," answered Dunston Porter.
"If they are going down a really steep hill, it's a wonder we don't hear some squeak from the brakes," was Phil's comment.
"Listen!" cried Dave, suddenly, and held up his hand.
All strained their ears once more, and now far below them they heard several cries mingled with a shriek. Then came a sudden crash, followed by more shrieks.
"They've had an accident!"
"Wonder what it was?"
"We'll have to go and see!" cried Dave, and put on the power once more.
"That's right!" cried Dunston Porter: "Get down there as fast as you can, Dave. But be careful—we don't want to run into them, or have any accident of our own. There must be something wrong down there!"