signal he sent vibrating from the steel sides of the tank. When
one arm tired he would use the other. He grew weary, his head was
aching, and there was a ringing in his ears; a ringing that seemed as
if ten thousand bells were jangling out their peals, and he could
barely distinguish his own pounding.

Signal after signal he sounded. It was becoming like a dream to him,
when suddenly, as he paused for a rest, he heard his name called
faintly, as if far away.

"Tom! Tom! Where are you?"

It was the voice of Mr. Sharp. Then followed the tones of the aged
inventor.

"My poor boy! Tom, are you still alive?"

"Yes, dad! In the starboard tank!" the lad gasped out, and then he lost
his senses. When he revived he was lying on a pile of bagging in the
submarine shop, and his father and the aeronaut were bending over him.

"Are you all right, Tom?" asked Mr. Swift.

"Yes--I--I guess so," was the hesitating answer. "Yes," the lad added,
as the fresh air cleared his head. "I'll be all right pretty soon. Have
you seen Andy Foger?"

"Did he shut you in there?" demanded Mr. Swift.

Tom nodded.

"I'll have him arrested!" declared Mr. Swift "I'll go to town as soon
as you're in good shape again and notify the police."

"No, don't," pleaded Tom. "I'll take care of Andy myself. I don't
really believe he knew how serious it was. I'll settle with him later,
though."

"Well, it came mighty near being serious," remarked Mr. Sharp grimly.
"Your father and I came back a little sooner than we expected, and as
soon as I got near the house I heard your signal. I knew what it was in
a moment. There were Mrs. Baggert and Garret talking away, and when I
asked them why they didn't answer your call they said they thought you
were merely tinkering with the machinery. But I knew better. It's the
first time we ever had a use for 'forty-seven,' Tom."

"And I hope it will be the last," replied the young inventor with a
faint smile. "But I'd like to know what Andy Foger is doing in this
neighborhood."

Tom was soon himself again and able to go to the house, where he found
Mrs. Baggert brewing a big basin of catnip tea, under the impression
that it would in some way be good for his. She could not forgive
herself for not having answered his signal, and as for Mr. Jackson, he
had started for a doctor as soon as he learned that Tom was shut up in
the tank. The services of the medical man were canceled by telephone,
as there was no need for h