Aloft with Tom and Jack were several other fighters, for it was not only considered a great honor to bring down a Zeppelin, but it would save many lives if one or more of the big gas machines could be prevented from dropping bombs on Paris or its environs.

The machines which were used were all of the single type, though of different makes and speeds. Each one was equipped with electric launching tubes. These were a somewhat new device for use against captive Hun balloons and Zeppelins and were installed in many of the fighting scout craft of the Americans and Allies.

Between the knees of Toni and Jack, as well as each of the other pilots, was a small metal tube. This went completely through the floor of the cockpit, so that, had it been large enough to give good vision, one could view through it the ground beneath.

In a little rack at the right of each scout were several small bombs of various kinds. Some were intended to set on fire whatever they came in contact with, being of phosphorus. Others were explosive bombs, pure and simple, while some were flares, intended to light up the scene at night and make getting a target easier.

Included in the rack of death and destruction was a simple stick; not unlike a walking cane, and this seemed so comparatively harmless that an uninitiated observer would almost invariably ask its use.

At the lower end of the launching tube, through which the bombs were dropped, was a “trip,” or sort of catch, that caught on a trigger fastened to each bomb. The trip pulled the trigger, so to speak, and set in operation the firing device.

In the early days, though doubtless the defect was afterwards corrected, the bombs sometimes stuck in the launching tube, and as they were likely to go off in this position at any moment, it was the custom of the pilots to push them on their way with the cane if the missiles jammed. Hence it was an essential part of each flying machine's armament.

Higher and higher mounted the fighting scouts, with Tom and Jack among their number. It was necessary to mount very high in order to get above the Zeppelins, as in this position alone was it possible for the aeroplanes to fight them to any advantage. The Zeppelins carried many machine guns of long range, and for the pigmy planes to attack them on the same level, meant destruction to the smaller craft.

There were several German machines in the raid toward Paris, but Tom and Jack caught sight of only two. The others were either at too great a height to be observed, or else were farther off, lost in the haze.

But the two silver shapes, resembling nothing so much as huge, expensive cigars, wrapped in tinfoil, were flying on their way, now and then dropping bombs, which exploded with dull, muffled reports—an earnest of what they would do when they got over Paris. They were traveling fast, under the impulse of their own powerful motors and propellers, and also aided by a stiff breeze.

Of course conversation was out of the question among Tom, Jack and the other aviators, but they knew the general plan of the fight. They were to get above the Zeppelins—as many of them as could—and drop bombs on the gas envelope. They were also to attack with machine guns if possible, aiming at the rudder controls and machinery. It was the great desire of the Allied commanders to have a Zeppelin brought down as nearly intact as possible.

Up and up climbed the speedy scout machines, and it was seen that some of them would never get in a position to do any damage. The German craft were traveling too speedily. But Tom and Jack managed to get to a height of about twenty thousand feet, which was above the Zeppelins, though by this time the Germans were in advance of them, for they had climbed at rather a steep angle. However, they knew their speed was many times that of the German machine on a straight course.

On and on they went. Then came a mist which hid the enemy from sight. The aviators railed at their luck, and Tom and Jack dropped down a bit, hoping to get through the mist. It lay below them like a great, gray blanket.

Suddenly they fairly plumped through it, and saw, not far away, the two big silver shapes, shining in the searchlights which were now giving good illumination. It was a moonlight night, which seemed a favorite for a German bombing expedition.

Far below them, and beneath the Zepplins, Tom and Jack could see the lights of other aeroplanes, which were flying low to observe lanterns on the ground, set in the shape of arrows, to indicate in which direction the German craft were traveling. Later, if necessary, these observing machines could climb aloft and signal to those higher up.

Nearer and nearer Jack and Tom came to one of the Zeppelins. And now, in the semi-darkness, they became aware that they were being fired at by a long-range gun on the German craft. The bullets sung about them, but though their machines were hit several times, as they learned later, they escaped injury.

Now the battle of the air was on in grim and deadly earnest. Several scout planes flew at the big Zeppelin like hornets attacking a bear. They fired their machine guns, and the Germans replied in kind, but with more terrible effect, for two of the Allied planes were shot down. It was a sad loss, but it was the fortune of war, or, rather, misfortune, for the Zeppelin was not engaged in a fair fight, but seeking to bomb an unfortified city.

Now Tom and Jack, though somewhat separated, were close above the Zeppelin, and in a position where they could not be fired at. They began to drop incendiary bombs through the tubes between their knees.

These bombs were fitted with sharp hooks, so that if they touched the gas bag they would cling fast, and burn until they had ignited the envelope and the vapor inside. And as they circled about, dropping bomb after bomb, the two air service boys saw this happen. Some at least of their bombs reached their target.

The great craft, now on fire in several places, was twisting and turning like some wounded snake, endeavoring to escape. Tom glanced toward the other Zeppelin and saw that this was fairly well surrounded by aeroplanes, but was not, as yet, on fire.

The bees had fatally stung one great German bear, and, a little later, it crashed to the ground where it was nearly all consumed, and of its crew of thirty men, not one was left alive.

The other plane, though greatly damaged by machine gun fire, was not set ablaze, but was forced to turn and sail for the German lines again. So that two were prevented from bombing Paris.

Well satisfied with what they had accomplished, Torn, Jack and the others who had set the Zeppelin on fire, descended. Later they learned, by word from Paris, that on of the German machines was shot down over that city and some of its crew captured. So that though the Huns did considerable damage with their bombs, they paid dearly for that unlawful expedition.

This was the beginning of a series of fierce aerial battles between the German forces and the Allied airmen, though for a long dine no more Zeppelins were seen. Sometimes fortune favored the side on which Tom and Jack fought, and again they were forced to retire, leaving some of their friends in the hands of the enemy.

Once Tom and Tack, keeping close together doing scout work, were cut off from their companions. They had ventured too far over the Hun lines, and were in danger of being shot down. But a squadron of airmen from Pershing's forces made a sortie and drove the Germans to cover, rescuing the two air service boys from an evil fate.

Then followed some weeks of rainy and misty weather, during which there was very little air work on either side. But the fight on land went on, with attacks and repulses, the Allies continually advancing their lines, though ever so little. Slowly but surely they were forcing the Germans back.

Now and then there were night raids, and once Tom and Jack, who had not flown for a week because of rain, were just back of the lines when a captured German patrol was brought in, covered with mud and blood. There had been lively fighting.

“I wish we were in on that!” exclaimed Tom. “I'm getting tired of sitting around.”'

“So am I!” agreed Jack. “Let's ask if we can't go out on patrol some night. It will be better than waiting for it to stop raining.”

To their delight their request was granted, as it had been in a number of other cases of airmen. Temporarily they were allowed to go with the infantry until the weather cleared.

The two air service boys were in the dugout one night, having served their turns at listening post work and general scouting, when an officer came in with a slip of paper. He began reading off some names, and when he had finished, having mentioned Tom and Jack, he said:

“Prepare for patrol duty at once.”

“Good!” whispered Tom to his chum: “Now there'll be something doing.”

He little guessed what it was to be.