book I picked up in Philadelphia, but I guess the book was more fiction

than fact."

Another silence ensued, and then Herc spoke. He took up the conversation where it had been left off.

"It's worth trying," he said in a matter-of-fact tone.

"What's worth trying?" asked Ned, through the darkness.

"Why Paul Jones' trick--or rather the trick he is supposed to have played."

"Oh, burning himself out of prison?"

"Yes."

"I don't see the connection with our case."

"Then you are a whole lot denser than I gave you credit for being."

"Thanks. But I see you've got an idea of some sort simmering in that massive brain of yours. What is it?"

"Just this, that we duplicate the trick."

"By ginger, Herc, there's nothing slow about you. You mean that we burn ourselves out of here?"

"That's just what I do. See any obstacles in the way?"

"A whole fleet of them. For one thing we'd suffocate ourselves if we tried to burn the door down, which is, I suppose, what you are driving at. Another thing--how about matches?"

"I've got lots of those. Now see here, Ned," went on Herc enthusiastically, "my plan may seem just moonshine, but it's worth trying. You know that little swinging trap at the bottom of the door?"

"Yes."

"Well, we can build our fire _outside_ the door by thrusting our fuel through it and out into the passage. My idea is that the flames will rise against the surface of the door, and if we make them hot enough will burn off the bolts without setting the whole door on fire. The oak is thick enough, I think, to remove all danger of that."

"Humph!" said Ned. "There's only one thing you haven't thought of, Herc."

"What's that?"

"What are we going to build a fire with?"

"With the same stuff as Paul Jones did--or rather stuff somewhat like it--the soft lining of these padded walls."

"Say, Herc, you're a wonder! I always said you had a great brain," cried Ned banteringly, "but hasn't it occurred to you that your fire would burn out the floor of the passage and set the place on fire before it would get the bolts hot enough to make them drop off?"

"It might if the floors and walls were not concrete. I noticed them as we came along," rejoined Herc in a quiet voice.

"Herc, you ought to be director of the Smithsonian Institute or--or something big," declared Ned admiringly. "It does begin to look as if we might have a chance to get out, after all. At any rate, it's worth trying. It will give us something to do."

"Of course it will," responded Herc cheerfully; "and now, if you'll switch on that light of yours, we'll start pulling the materials for our fire off these walls."

It didn't take long to rip out a great pile of the batting and shavings with which the walls were stuffed. These were thrust through the hole in the bottom of the door into the passage outside as fast as they were pulled out. At last the pile was declared large enough, and, with a big heap in reserve for use when the other had burned out, the boys prepared to light the mass of inflammable stuff.

It blazed up fiercely when the match was applied, but, of course, as it was outside the door in the concrete passage, the flames did not bother the boys or imperil the building. On their hands and knees the two young prisoners crouched, feeding the flames assiduously when they showed signs of dying down. There was plenty of fuel, and a roaring fire was maintained.

All at once there was a soft thud outside the door, and something dropped into the flames. It was one of the heavy bolts which had torn loose from its charred and weakened fastenings. A few minutes later another crash announced that the second one had fallen.

The lads waited a few minutes, till the fire died down, and then, with beating hearts, they put their shoulders to the door.

"Heave!" roared Ned, and the next moment, under their united efforts, the remaining bolt tore loose from its blackened foundations, and the two Dreadnought Boys stood outside in the smoke-filled passage.

"Let's give three cheers!" cried Herc.

"Better be careful about making a noise," counselled Ned. "No telling but some of those rascals may be hiding in the building somewhere."

"That's right," agreed Herc. "Another thing has occurred to me, too. All the windows of this delightful place are barred, and if the door has been locked and the place vacated, we're going to have a hard time to get out, even now."

"That's right. Well, we'd better start on our tour of exploration right away."

Guided by Ned, with his torch ready for instant darkening, the two lads began to thread the maze of corridors and passages. They had been doing this for several minutes, and were beginning to get rather bewildered, when Ned stopped suddenly just as they entered a long corridor pierced with doors, with the same monotonous regularity as the others. He extinguished the light in the wink of an eye, and drew Herc swiftly into the embrasure of a doorway as he did so.

Far down the corridor a footstep had sounded, and another light had flashed. As they crouched in the darkness, prepared for any emergency, a sudden voice sounded from the end of the corridor:

"Stop right where you are, or I'll fire!"