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 sh.e.l.l 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 sh.e.l.l 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 sh.e.l.ls 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 compa.s.s, 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 sh.e.l.ls. 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 G.o.d-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.

CHAPTER VI. IN PARIS

Attired in their natty uniforms of the La Fayette Escadrille, which they had not discarded, with the double wings showing that they were fully qualified pilots and aviators, Jack Parmly and Tom Raymond attracted no little attention as, several hours after leaving their places on the battle front, they arrived in Paris. They were to have a few days rest before joining the newly formed American aviation section which, as yet, was hardly ready for active work.

"Well, they're here!" suddenly cried Tom, as he and Jack made their way out of the station to seek a modest hotel where they might stay until time for them to report.

"Who? Where? I don't see 'em!" exclaimed Jack, as he crowded to the side of his chum, murmurs from a group of French persons testifying to the esteem in which the American lads were held.

"There!" went on Tom, pointing. "See some of our doughboys! And maybe the crowds aren't glad to have 'em here! It's great, I tell you, great!"

As he spoke he pointed to several khaki-clad infantrymen, some of the first of the ten thousand Americans lads that were sent over to "take the germ out of Germany." The Americans were rather at a loss, but they seemed masters of themselves, and laughed and talked with glee as they gazed on the unfamiliar scenes. They, too, were enjoying a holiday before being sent on to be billeted with the French or British troops.

"Come on, let's talk to 'em!" cried Tom, enthusiastically. "It's as good as a letter from home to see 'em!"

"I thought you meant you saw--er--Bessie and her mother," returned Jack, and there was a little disappointment in his voice.

"Oh, we'll see them soon enough, if they're still in Paris," said Tom, gazing curiously at his chum. "But they don't know we are coming here."

"Yes, they do," said Jack, quietly.

"They do? Then you must have written."

"Of course. Don't you want to see them before we get shipped off to a new sector?"

"Why, yes. Just now, though, I'm anxious to hear some good, old United States talk. Come on, let's speak to 'em. There's one bunch that seems to be in trouble."

But the trouble was only because some of Pershing's boys--as they were generally called wanted to make some purchases at a candy shop and did not know enough of the language to make their meaning clear. It was a good-natured misunderstanding, and both the French shop-keeper and his helper and the doughboys were laughing over it.