The answer came in a hollow, echoing sound, which indicated that Harry Girdwood had made some considerable progress.
This increased his eagerness greatly.
* * * * *
"Harry."
No answer.
He was too far for young Jack's voice to reach him.
Quitting his post at the door, young Jack ran back to the hole in the wall, and called out eagerly to his exploring comrade—
"Harry, Harry!"
"Hullo!"
"Come back, quick! I can hear someone coming."