But this took many hours, and it was not until the second day of their captivity that they had the hole nearly large enough for the passage of one person at a time.  They had not been discovered, they thought.

Meanwhile they had been given food and water at intervals, but to all demands that they be released, or at least told why they were held prisoners, a deaf ear was turned.

They could only guess at the fate of Koku.  Probably the giant was kept bound, for once he got the chance to use his enormous strength it might go hard with the foreigners.

The Mars continued to fly through the air.  Sometimes, as Tom and his friends could tell by the motion, she was almost stationary in the upper regions, and again she seemed to be flying at top speed.  Occasionally there came the sound of firing.

“They’re trying my guns,” observed Tom grimly.

“Do you suppose they are being attacked?” asked Ned, hopefully.

“Hardly,” replied Captain Warner.  “The United States possesses no craft able to cope with this one in aerial warfare, and they are hardly engaging in part of the European war yet.  I think they are just trying Tom’s new guns.”

Later our friends learned that such was the case.

The storm had either passed, or the Mars had run out of the path of it, for, after the first few hours of pitching and tossing, the atmosphere seemed reduced to a state of calm.

All the while they were secretly working to gain their freedom so they might attack and overpower their enemies, they took occasional observations from the small window.  But they could learn nothing of their whereabouts.  They could only view the heaving ocean, far below them, or see a mass of cloud-mist, which hid the earth, if so be that the Mars was sailing over land.

“But how much longer can they keep it up?” asked Ned.

“Well, we have fuel and supplies aboard for nearly two weeks,” Tom answered.

“And by the end of that time we may all be dead,” spoke the young bank clerk despondently.

“No, we’ll be out of here before then!” declared Lieutenant Marbury.

Indeed the hole was now almost large enough to enable them to crawl out one at a time.  They could not, of course, see how it looked from the outside, but Tom had selected a place for its cutting so that the sawdust and the mark of the panel that was being removed, would not ordinarily be noticeable.

Their set night as the time for making the attempt—­late at night, when it was hoped that most of their captors would be asleep.

Finally the last cut was made, and a piece of wood hung over the opening only by a shred, all ready to knock out.

“We’ll do it at midnight,” announced Tom.

Anxious, indeed, were those last hours of waiting.  The time had almost arrived for the attempt, when Tom, who had been nervously pacing to and fro, remarked: