On and on sped Tom, sparing time, now and then, to look back at his pursuers, who were, it could not be doubted, doing their best to get within effective range. And, every now and again, Tom would glance at the motionless form of his churn.

But poor Jack never stirred, and Tom was fearing more and more that his chum had made his last flight. As for the Hun aviators, after using up a drum or so of bullets uselessly, they ceased firing and urged their machine on to the uttermost.

But Tom had the start of them, and he was also on a higher level, so that the Germans must climb at an oblique angle to reach him.

And, thanks to this, Tom saw that, if nothing else happened, he would soon be in comparative safety with the unconscious form of Jack. The anti-aircraft batteries were firing in vain, as he was beyond their range, and, far away, he could see the lines of the French armies, behind which he soon hoped to be.

And then the unexpected happened, or, rather, it had taken place some time since, but it was only then brought to Tom's attention. His engine began missing, and when he sought for a cause he speedily found it.

Nearly all the gasoline had leaked out of the main tank. As he knew that there had been plenty for the return flight, there was but one explanation of this. A Hun bullet had pierced the petrol reservoir, letting the precious fluid leak away.

"Now if the auxiliary tank has any in it, I'm fairly all right," thought Tom. "If it hasn't, I'm all in."

His worst fears were confirmed, for the auxiliary tank had suffered a like fate with the main one. Both were pierced. There were only a few drops left, besides those even then being vaporized in the carburetor.

With despair in his heart, Tom looked back. If the Hun plane chose to rush him now all would be over with him and Jack. He had only enough fuel for another thousand meters or so, and then he must volplane.

He saw a burst of flame and smoke from the enemy plane, and realized that he was being shot at again. But the distance was still too far for effective aim.

And then, to his joy, Tom saw the pursuer turn and start back toward the German territory. The firing had been a last, desperate attempt to end his career, and it had failed. Either the Huns were almost out of petrol themselves, or they did not relish getting too close to the French lines.

"And now, if I can volplane down the rest of the way, I'll be in a fair position to save myself," mused Tom, as he made a calculation of the distance he had yet to go. It was far, but he was at a good height and believed he could do it.

Suddenly his engine stopped, as though with a sigh of regret that it could no longer serve him, and Tom knew that volplaning alone would save him now. He was still over the enemy country, and had his plight been guessed at by the Germans, undoubtedly they would have sent a machine up to attack him. But they were in ignorance.

There was nothing to do but drift along. Gravity alone urged the craft on. As he swept over the German trenches Tom was greeted with a burst of shrapnel, and he was now low enough to be vulnerable to this. But luck was with him, and though the plane was. .h.i.t several times he thought he was unharmed. But in this he was wrong. He received a glancing wound in one leg, but in the excitement he did not notice it, and it was not until he had landed that he saw the blood, and knew what had happened.

On and on, and down and down he volplaned until he was so near his own lines, and so low down, that he could hear the burst of cheers from his former comrades.

Then he aimed his craft for a level, gra.s.sy place to make a landing, and as he came to a gradual stop, and was surrounded by a score of eager aviators, he cried out, as soon as he could speak, "I'm all right! But look after Jack! He's hurt!"

A surgeon bent hastily over the huddled form, and with the aid of some men lifted it from the c.o.c.kpit. Jack's legs were covered with blood, and when the medical man saw whence it came, then and there he set hastily to work to stop the bleeding from a large artery.

"You got back only just in time, my friend," he said to Tom, as Jack was carried to a hospital. "Two minutes more and he would have been bled to death."

CHAPTER XVII. A CRASH

Not until a day or so later, when Jack was able to sit up in bed and greet Tom with rather a pale face, did the latter learn all that had happened. And it was a very close call that Jack had had.

As Tom had guessed, it was some of the bullets from the Hun machine gun that had stricken down his chum. One had struck him a glancing blow on the head, rendering Jack unconscious and sending him down, a crumpled-up heap in the c.o.c.kpit of his machine. Another bullet, coming through the machine later, had found lodgment in Jack's leg, cutting part way through the wall of one of the larger arteries.

It was certain that this bullet, the one in the leg, came after Jack was. .h.i.t on the head, for that first wound was the only one he remembered receiving.

"It was just as though I saw not only stars' but moons, suns, comets, rainbows and northern lights all at once," he explained to his chum.

The bullet in the leg had cut only part way through the wall of an artery. At first the tissues held the blood back from spurting out in a stream that would soon have carried life with it. But either some unconscious motion on Jack's part, or a jarring of the plane, broke the half-severed wall, and, just before Tom landed, his chum began to bleed dangerously. Then it was the surgeon had made his remark, and acted in time to save Jack's life.

"Well, I guess we made good all right," remarked Jack, as his chum visited him in the hospital.

"I reckon so," was the answer, "though the Huns haven't sent us any love letters to say so. But we surely did drop the packages in the prison camp, though whether Harry got them or not is another story. But we did our part."

"That's right," agreed Jack. "Now the next thing is to get busy and bring Harry out of there if we can."

"The next thing for you to do is to keep quiet until that wound in your leg heals," said the doctor, with a smile. "If you don't, you won't do any more flying, to say nothing of making any rescues. Be content with what you did. The whole camp is talking of your exploit. It was n.o.ble!"

"Shucks!" exclaimed Tom, in English, for they had been speaking French for the benefit of the surgeon, who was of that nationality.

"Ah, and what may that mean?" he asked.

"I mean it wasn't anything," translated Tom. "Anybody could have done what we did."

But of this the surgeon had his doubts.

In spite of the dangerous character of his wound, Jack made a quick recovery. He was in excellent condition, and the wound was a clean one, so, as soon as the walls of the artery had healed, he was able to be about, though he was weak from loss of blood. However, that was soon made good, and he and Tom, bidding farewell to their late comrades, returned to the American lines. They had been obliged to get an extension of leave--at least Jack had--though Tom could report back on time, and he spent the interim between that and Jack's return to duty, serving as instructor to the "huns" of his own camp. They were eager to learn, and anxious to do things for themselves.

Before long Jack returned, though he was not a.s.signed to duty, and he and Tom visited Paris and told Nellie, Bessie and Mrs. Gleason the result of their mission.

"You didn't see Harry, of course?" asked Nellie, negatively, though really hoping that the answer would be in the affirmative.

"Oh, no, we couldn't make out any individual prisoner," said Tom. "There was a bunch of 'em--I mean a whole lot--there."

"Poor fellows!" said Mrs. Gleason kindly, "Let us hope that they will soon be released."

"Tom and I have been trying to hit on some plan to rescue Harry," put in Jack. "And we'd help any others to get away that we could. But is isn't going to be easy."

"Oh, I don't see how you can do it!" exclaimed Nellie. "Of course I would give anything in the world to have Harry back with me, but I must not ask you to run into needless danger on his account. That would be too much. Your lives are needed here to beat back the Huns. Harry may live to see the day of victory, and then all will be well."

"I don't believe in waiting, if anything can be done before that." Tom spoke grimly. "But, as Jack says, it isn't going to be easy," he went on. "However, we haven't given up. The only thing is to hit on some plan that's feasible."

They talked of this, but could arrive at nothing. They were not even sure--which made it all the harder to bear--that Harry had received the packages dropped in the prison camp at such risk. The only thing that could be done was to wait and see if he wrote to his sister or his former chums. Letters occasionally did come from German prisoners, but they were rare, and could be depended on neither as to time of delivery nor as to authenticity of contents.

So it was a case of waiting and hoping.

Jack was not yet permitted to fly, so Tom had to go alone. But he served as an instructor, leaving the more dangerous work of patrol, fighting, and reconnaissance to others until he was fit to stand the strain of flying and of fighting once more.

"Sergeant Raymond, you will take up Martin to-day," said the flight lieutenant to Tom one morning. "Let him manage the plane himself unless you see that he is going to get into trouble. And give him a good flight."

"Yes, sir," answered Tom, as he turned away, after saluting.

He found his pupil, a young American from the Middle West, who was not as old as he and Jack, awaiting him impatiently.

"I'm to get my second wing soon, and I want to show that I can manage a plane all by myself, even if you're in it," said the lad, whose name was d.i.c.k Martin. "They say I can make a solo flight to-morrow if I do well to-day."

"Well, go to it!" exclaimed Tom with a laugh. "I'm willing."

Soon they were in a double-seater of fairly safe construction--that is, it was not freakish nor speedy, and was what was usually used in this instructive work.