"Ha!" exclaimed the doctor suddenly, "I smell petrol."
All of us at once stopped and raised our heads. There certainly was a strange taint in the air but it was not that of petrol, I was certain.
"Poof," I said, frowning as if I were puzzled. "It's not petrol. It's oil."
"Well, it's all the same," exclaimed the doctor excitedly, "a car's been here."
But I knew what had happened. When I had thrown the machine over to file out the engine number some of the oil must have trickled away down in the sand, and now the intense heat was volatilising it.
The doctor let go my arm, and began frenziedly rushing round searching for wheel marks, when suddenly a vivid flash of lightning leapt through the gloom and immediately a violent clap of thunder followed.
"Quick!" shouted Willoughby, "back to
