“But smoke doesn’t always mean a campfire. Come on, let’s have a look at the engine.”

They went carefully over the machinery, the perfect working of which was so vital to their safety. It did not take Jerry long to discover what the trouble was.

“Look!” he cried. “One of the carburetors is smashed.”

“Smashed!” echoed Ned.

“Yes. No wonder we couldn’t get any explosions, even when the self starter spun the propellers. She wasn’t getting any gas, and the spare carburetor wasn’t in service.”

“But what would make it break?” asked Ned.

“That’s what we’ve got to find out,” Jerry stated. “Did you hear a sort of click just before the machinery stopped working?”

“Yes,” assented Ned, “and I wondered what caused it.”

Jerry was looking with careful and eager eyes over different parts of the powerful motor.