Chapter Four. Tom is Imprisoned

"Well, I must say he's a cool one," remarked Tom, as the echoes of Mr. Berg's steps died away. "The idea of thinking his boat better than ours! I don't like that man, dad. I'm suspicious of him. Do you think he came here to steal some of our ideas?"

"No, I hardly believe so, my son. But how did you discover him?"

"Just as you saw, dad. I heard a noise and went back there to investigate. I found him sneaking around, looking at the electric propeller plates. I went to grab him just as he stumbled over a hoard. At first I thought it was one of the old gang. I'm almost sure he was trying to discover something."

"No, Tom. the firm he works for are good business men, and they would not countenance anything like that. They are heartless competitors, however, and if they saw a legitimate chance to get ahead of me and take advantage, they would do it. But they would not sneak in to steal my ideas. I feel sure of that. Besides, they have a certain type of submarine which they think is the best ever invented, and they would hardly change at this late day. They feel sure of winning the Government prize, and I'm just as glad we're not going to have a contest."

"Do you think our boat is better than theirs?"

"Much better, in many respects."

"I don't like that man Berg, though," went on Tom.

"Nor do I," added his father. "There is something strange about him. He was very anxious that I should compete. Probably he thought his firm's boat would go so far ahead of ours that they would get an extra bonus. But I'm glad he didn't see our new method of propulsion. That is the principal improvement in the Advance over other types of submarines. Well, another week and we will be ready for the test."

"Have you known Mr. Berg long, dad?"

"Not very. I met him in Washington when I was in the patent office. He was taking out papers on a submarine for his firm at the same time I got mine for the Advance. It is rather curious that he should come all the way here from Philadelphia. merely to see if I was going to compete. There is something strange about it, something that I can't understand."

The time was to come when Mr. Swift and his son were to get at the bottom of Mr. Berg's reasons, and they learned to their sorrow that he had penetrated some of their secrets.

Before going to bed that night Tom and Mr. Sharp paid a visit to the shed where the submarine was resting on the ways, ready for launching. They found Mr. Jackson on guard and the engineer said that no one had been around. Nor was anything found disturbed.

"It certainly is a great machine," remarked the lad as he looked up at the cigar-shaped bulk towering over his head. "Dad has outdone himself this trip."

"It looks all right,"