as Tom was rather tired, he went directly to his own room, and, a
little later got into bed.

It was shortly after midnight when he was awakened by hearing a
rattling on the window of his room. The reason he was able to fix
the time so accurately was because as soon as he awakened he
pressed a little electric button, and it illuminated the face of
a small clock on his bureau. The hands pointed to five minutes
past twelve.

"Humph! That sounds like hail!" exclaimed Tom, as he arose, and
looked out of the casement. "I wonder if any of the skylights of
the airship shed are open? There might be some damage. Guess I'd
better go out and take a look."

He had mentally reasoned this far before he had looked out, and
when he saw that the moon was brightly shining in a clear sky, he
was a bit surprised.

"Why--that wasn't hail," he murmured. "It isn't even raining. I
wonder what it was?"

He was answered a moment later, for a shower of fine gravel
from the walk flew up and clattered against the glass. With a
start, Tom looked down, and saw a dark figure standing under an
apple tree.

"Hello! Who's there?" called the lad, after he had raised the
sash.