“Look, Al! What’s that?”

“Why, it looks like—It is! It’s a signal light!

“And calling us—KX!” cried Alex. “Something must be wrong with Wilson!”

“What’ll we do? Back to the train?”

“Have you a match and some paper?” said Alex, going hurriedly through his own pockets.

“Some matches.”

“Here’s a couple of letters. Come on back to the rails, find some chips, and make a fire. See if we can’t answer him, and learn what the trouble is.”

They were already racing for the track, reached it, and quickly gathering together a little pile of dry bark and chips knocked from the ties, made a fire at the track-side, and lit it.

As the flames burst up Alex threw off his coat, and using it as a curtain, raised and lowered it in a flashed “I, I, KX!”

The call twinkled on. Wilson had not seen it. But the next moment, before Alex had completed a second answer, the red light disappeared. Alex again shot forth the gleaming “I, I, KX!” and in blinking response they read: