"Thank you," he gasped out, in one last despairing effort. "Things
look very black; but while there's life there's hope. They may even
still, perhaps, come up with us."

As he spoke, a sound broke unexpectedly on the silence of their
prison. A dull thud seemed to make itself faintly heard from beyond
the thick wall of sand that cut them off from the daylight. Cyril
stared with surprise. It was a noise like a pick-axe. Stooping
hastily down, he laid his ear against the rail beside the shattered
carriage.

"They're digging!" he cried earnestly, finding words in his joy.
"They're digging to reach us! I can hear them! I can hear them!"

Elma glanced up at him with a certain tinge of half-incredulous
surprise.

"Yes, they're digging, of course," she said quickly. "I knew they'd
dig for us, naturally, as soon as they missed us. But how far off
are they yet? That's the real question. Will they reach us in time?
Are they near or distant?"

Cyril knelt down on the ground as before, in an agony of suspense,
and struck the rail three times distinctly with his walking-stick.
Then he put his ear to it and listened, and waited. In less than
half a minute three answering knocks rang, dim but unmistakable,
along the buried rail. He could even feel the vibration on the iron
with his face.