On this subject there was no fear of dispute.

"And your servant?" said Phil Evans, pointing to Frycollin, who was puffing like a grampus. "We must set him free."

"Not yet," said Uncle Prudent. "He would overwhelm us with his jeremiads, and we have something else to do than abuse each other."

"What is that, Uncle Prudent?"

"To save ourselves if possible."

"You are right, even if it is impossible."

"And even if it is impossible."

There could be no doubt that this kidnapping was due to Robur, for an ordinary thief would have relieved them of their watches, jewelry, and purses, and thrown their bodies into the Schuyllkill with a good gash in their throats instead of throwing them to the bottom of--Of what? That was a serious question, which would have to be answered before attempting an escape with any chance of success.

"Phil Evans," began Uncle Prudent, "if, when we came away from our meeting, instead of indulging in amenities to which we need not recur, we had kept our eyes more open, this would not have happened. Had we remained in the streets of Philadelphia there would have been none of this. Evidently Robur foresaw what would happen at the club, and had placed some of his bandits on guard at the door. When we left Walnut Street these fellows must have watched us and followed us, and when we imprudently ventured into Fairmount Park they went in for their little game."

"Agreed," said Evans. "We were wrong not to go straight home."

"It is always wrong not to be right," said Prudent.

Here a long-drawn sigh escaped from the darkest corner of the prison. "What is that?" asked Evans.

"Nothing! Frycollin is dreaming."

"Between the moment we were seized a few steps out into the clearing and the moment we were thrown in here only two minutes elapsed. It is thus evident that those people did not take us out of Fairmount Park."

"And if they had done so we should have felt we were being moved."

"Undoubtedly; and consequently we must be in some vehicle, perhaps some of those long prairie wagons, or some show-caravan --"

"Evidently! For if we were in a boat moored on the Schuyllkill we should have noticed the movement due to the current --"

"That is so; and as we are still in the clearing, I think that now is the time to get away, and we can return later to settle with this Robur --"

"And make him pay for this attempt on the liberty of two citizens of the United States."

"And he shall pay pretty dearly!"

"But who is this man? Where does he come from? Is he English, or German, or French --"

"He is a scoundrel, that is enough!" said Uncle Prudent. "Now to work." And then the two men, with their hands stretched out and their fingers wide apart, began to feel round the walls to find a joint or crack.

Nothing. Nothing; not even at the door. It was closely shut and it was impossible to shoot back the lock. All that could be done was to make a hole, and escape through the hole. It remained to be seen if the knives could cut into the walls.

"But whence comes this never-ending rustling?" asked Evans, who was much impressed at the continuous f-r-r-r.

"The wind, doubtless," said Uncle Prudent.

"The wind! But I thought the night was quite calm."

"So it was. But if it isn't the wind, what can it be?"

Phil Evans got out the best blade of his knife and set to work on the wall near the door. Perhaps he might make a hole which would enable him to open it from the outside should it be only bolted or should the key have been left in the lock. He worked away for some minutes. The only result was to nip up his knife, to snip off its point, and transform what was left of the blade into a saw.

"Doesn't it cut?" asked Uncle Prudent.

"No."

"Is the wall made of sheet iron?"

"No; it gives no metallic sound when you hit it."

"Is it of ironwood?"

"No; it isn't iron and it isn't wood."

"What is it then?"

"Impossible to say. But, anyhow, steel doesn't touch it." Uncle Prudent, in a sudden outburst of fury, began to rave and stamp on the sonorous planks, while his hands sought to strangle an imaginary Robur.