“Well, to-morrow, if all goes well, we'll be with Pershing's boys,” remarked Jack, as he and Tom were sitting in their quarters after breakfast, the last day but one they were to spend in the Lafayette Escadrille with which they had so long been associated.

“That's so. We'll soon be on the firing line with Uncle Sam,” agreed Tom. “Of course we've been with him, in a way, ever since we've been fighting, for it's all in the same cause. But there'll be a little more satisfaction in being 'on our own,' as the English say.”

“You're right. What's on for to-day?” asked Jack.

“Haven't the least idea. But here comes a messenger now.”

As Tom spoke he glanced from a window and saw an orderly coming toward their quarters. The man seemed in a hurry.

“Still I'm not giving up,” returned Jack. “I can't explain why, but I have a feeling that, some day, we'll see Harry Leroy again.”

Tom shook his head.

“I wish I could be as hopeful as you,” he said. “Maybe we'll see him again—or his grave. But I want to say, right now, that if ever I have a chance at the Hun who shot him down, that Hun Will get no mercy from me!”

“Same here!” echoed Jack. “But here comes the orderly.”

The man entered and handed Jack a slip of paper. It was from the commander of their squadron, and said, in effect, that though Tom and Jack were no longer under his orders, having been duly transferred to another sector, yet he would be obliged if they would call on him, at his quarters.

“Maybe he has news!” exclaimed Jack, eagerly.

Again Tom shook his head.

“He'd have said so if that was the case,” he remarked as he and his chum prepared to report at headquarters, telling the messenger they would soon follow him.

“Ah, young gentlemen, I am glad to see, you!” exclaimed the commander, and it was as friends that he greeted Tom and Jack and not as military subordinates. “Do you want to do me one last favor?”

“A thousand if we can!” exclaimed Jack, for he and Tom had caught something of the French enthusiasm of manner, from having associated with the brave airmen so long.

“Good! Then I shall feel free to ask. Know then, that I am a little short-handed in experienced airmen. The Huns have taken heavy toll of us these last few days,” he went on sorrowfully, and Torn and Jack knew this to be so, for two aces, as well as some pilots of lesser magnitude, had been shot down. But ample revenge had been taken.

“By all rights you are entitled to a holiday before you join your new command, under the great Pershing,” went on the flight commander. “However, as I need the services of two brave men to do patrol duty, I appeal to you. There is a machine gun nest, somewhere in the Boche lines, that has been doing terrible execution. If you could find the battery, and signal its location, we might destroy it with our artillery, and so save many brave lives for France,” he went on. “I do not like to ask you—”

“Tell 'em to get out the machines!” interrupted Jack. “We were just wishing we could do something to make up for the loss of Harry Leroy, and this may give it to us. You haven't heard anything of him, have you?” he asked.

The commander shook his head.

“I fear we shall never hear from him,” he said. “Though only yesterday we received back some of the effects of one of our men who was shot down behind their lines. I can not understand in Leroy's case.”

“Well, we'll make 'em pay a price all right!” declared Tom. “And now what about this machine gun nest?”

The commander gave them such information as he had. It was not unusual, such work as Tom and Jack were about to undertake. As the officer had said, they were practically exempt now that they were about to be transferred. But they had volunteered, as he probably knew they would.

Two speedy Spad machines were run out for the use of Tom and Jack, each one to have his own, for the work they were to do was dangerous and they would have need of speed.

They looked over the machine guns to see that they were in shape for quick work, and as the one on the machine Tom selected had congealed oil on the mechanism, having lately returned from a high flight, another weapon was quickly attached. Nothing receives more care and attention at an aerodrome than the motor of the plane and the mechanism of the machine gun. The latter are constructed so as to be easily and quickly mounted and dismounted, and at the close of each day's flight the guns are carefully inspected and cleaned ready for the morrow.

“Locate the machine gun battery if you can,” was the parting request to Tom and Jack as they prepared to ascend. “Send back word of the location as nearly as you can to our batteries, and the men there will see to the rest.”

“We will!” cried the Americans.

Locating a machine gun nest is not as easy as picking out a hostile battery of heavier guns, for the former, being smaller, are more easily concealed.

But Tom and Jack would, of course, do their best to help out their friends, the French. Over toward the German lines they flew, and began to scan with eager eyes the ground below them. They could not fly at a very great height, as they needed to be low down in order to see, and in this position they were a mark for the anti-aircraft guns of the Huns.

They had no sooner got over the enemy trenches, and were peering about for the possible location of the machine gun emplacement, when they were greeted with bursts of fire. But by skillfully dodging they escaped being hit themselves, though their machines were struck. The two chums were separated by about a mile, for they wanted to cover as much ground as possible.

At last, to his great delight, Tom saw a burst of smoke from a building that had been so demolished by shell fire that it seemed nothing could now inhabit it. But the truth was soon apparent. The machine gun nest was in the cellar, and from there, well hidden, had been doing terrible execution on the allied forces. Pausing only to make sure of his surmise, Tom began to tap out on his wireless key the location of the hidden machine gun nest.

Most of the aeroplanes carry a wireless outfit. An aerial trails after them, and the electric impulses, dripping off this, so to speak, reach the battery headquarters. Owing to the noise caused by the motor of the airship, no message can be sent to the airman in return, and he has to depend on signs made on the ground, arrows or circles in white by day and lighted signals at night, to make sure that his messages are being received and understood.

The Allies, of course, possess maps of every sector of the enemy's front, so that by reference to these maps the aircraft observer can send back word as to almost the precise location of the battery which it is desired to destroy.

Quickly tapping out word where the battery was located, Tom awaited developments, circling around the spot in his machine. He was fired at from guns on the ground below, but, to his delight, no hostile planes rose to give him combat. A glance across the expanse, however, showed that Jack was engaging two.

“He's keeping them from me!” thought Tom, and his heart was heavy, for he realized that Jack might be killed. However, it was the fortune of war. As long as the Hun planes were fighting Jack they would not molest him, and he might have time to send word to the French battery that would result in the destruction of the Hun machine nest.

There came a burst of fire from the Allied lines he had left, and Tom saw a shell land to the left and far beyond the Hun battery hidden in the old ruins. He at once sent back a correcting signal.

The more a gun is elevated up to a certain point, the farther it shoots. Forty-three degrees is about the maximum elevation. Again, if a gun is elevated too high it shoots over instead of directly at the target aimed at. It is then necessary to lower the elevation. Tom has seen that the guns of the French battery, which were seeking to destroy the machine gun nest were shooting beyond the mark. Accordingly they were told to depress their muzzles.

This was done, but still the shells fell to the left, and an additional correction was necessary. It is comparatively easy to make corrections in elevation or depression that will rectify errors in shooting short of or beyond a mark. It is not so easy to make the same corrections in what, for the sake of simplicity, may be called right or left errors, that is horizontal firing. To make these corrections it becomes needful to inscribe imaginary circles about the target, in this case the machine gun nest.

These circles are named from the letters of the alphabet. For instance, a circle drawn three hundred yards around a Hun battery as a center might be designated A. The next circle, two hundred yards less in size, would be B and so on, down to perhaps five yards, and that is getting very close.

The circles are further divided, as a piece of pie is cut, into twelve sectors, and numbered from 1 to 12. The last sector is due north, while 6 would be due south, 3 east, and 9 west, with the other figures for northeast, southwest, and so on.

If a shot falls in the fifty-yard circle, indicated by the letter D, but to the southwest of the mark, it is necessary to indicate that by sending the message “D-7,” which would mean that, speaking according to the points of the compass, the missile had fallen within fifty yards of the mark, but to the south-southwest of it, and correction must be made accordingly.

Tom watched the falling shells. They came nearer and nearer to the hidden battery and at last he saw one fall plump where it was needed. There was a great puff of smoke, and when it had blown away there was only a hole in the ground where the ruins had been hiding the machine guns.

Tom's work was done, and he flew off to the aid of Jack, who had overcome one Hun, sending his plane crashing to earth. But the other, an expert fighter, was pressing him hard until Ton opened up on him with his machine gun. Then the German, having no stomach for odds, turned tail and flew toward his own lines.

“Good for you, Tom!” yelled Jack, though he knew his chum could not hear him because of the noise of the motor.

Together the two lads, who had engaged in their last battle strictly with the French, made for their aerodrome, reaching it safely, though, as it was learned when Jack dismounted, he had received a slight bullet wound in one side from a missile sent by one of the attacking planes. But the hurt was only a flesh wound; though, had it gone an inch to one side, it would have ended Jack's fighting days.

Hearty and enthusiastic were the congratulations that greeted the exploit of Torn in finding the German machine gun nest that had been such a menace, nor were the thanks to Jack any less warm, for without his help Tom could never have maintained his position, and sent back corrections to the battery which brought about the desired result.

“It is a glorious end to your stay with us,” said the commander, with shining eyes, as he congratulated them.

There was a little impromptu banquet in the quarters that night, and Tom and Jack were bidden God-speed to their new quarters.

“There's only one thing I want to say!” said Jack quietly, as he rose in response to a demand that he talk.

“Let us hear it, my slice of bacon!” called a jolly ace.

“It's this,” went on Jack. “That I hereby resolve that if we—I mean Tom and I—can't rescue our comrade, Harry Leroy, from the Huns—provided he's alive—that we'll take a toll of five Germans for him—or as many, up to that number, as we can shoot down before they get us. Five German fliers is the price of Harry Leroy, who was worth a hundred of them!”

“Bravo! Hurrah! So he was! Death to the Huns!” were the cries.

Torn Raymond sprang to his feet

“What Jack says I say!” he cried. “But I double the toll. If Harry Leroy is dead he leaves a sister. You all saw her here! Well, I'll get five Huns for her, and that makes ten between Jack and me!”

“Success to you!” cried several.

With this resolve to spur them on, Tom and Jack bade their bravo comrades farewell and started for Paris, whence they were to journey to the headquarters of General Pershing and his men.