The plunging monster glided by.—Page [38].

THE BOY AVIATORS

WITH

THE AIR RAIDERS

A Story of the Great World War

BY

CAPTAIN WILBUR LAWTON

AUTHOR OF “THE DREADNOUGHT BOYS’ SERIES,” “THE BOY AVIATORS IN

NICARAGUA,” “THE BOY AVIATORS ON SECRET SERVICE,” “THE

BOY AVIATORS IN AFRICA,” “THE BOY AVIATORS’ TREASURE

QUEST,” “THE BOY AVIATORS IN RECORD FLIGHT,”

“THE BOY AVIATORS’ POLAR DASH,” “THE BOY

AVIATORS’ FLIGHT FOR A FORTUNE,” ETC.

WITH ILLUSTRATIONS BY

CHARLES L. WRENN

NEW YORK

HURST & COMPANY

PUBLISHERS

Copyright, 1915,

BY

HURST & COMPANY

CONTENTS

The Boy Aviators with the Air Raiders.

CHAPTER I.
NOT FAR FROM THE FIRING LINE.

“It seems queer not to have Harry along with us on this trip to the war zone of Europe!”

“Just what Pudge, here, was saying last night, Billy. But you know my brother Harry has been ordered by Doctor Perkins to keep quiet for two whole months.”

“Frank, he was lucky to break only his arm and collar bone, when it might have been his neck, in that nasty fall. But why are you rubbing your eyes like that, I’d like to know, Pudge Perkins?”

“Pirates and parachutes, I’ll tell you why, Billy. Every little while I get to thinking I must be dreaming. So I pinch myself, and dig my knuckles in my eyes to make sure. But it’s the real thing, isn’t it, boys?”

“If you mean that the three of us, here, representing the Sea Eagle Company, Limited, of Brig Island, in Casco Bay, Maine, makers of up-to-date seaplanes, have come over to look up a sample shipment of our manufactures, and find ourselves being pestered by the French and British Governments to take a contract from them, why it certainly is the real thing.”

“It was lucky my father has that arrangement with the French Government to protect our property through thick and thin,” continued the boy called Pudge, who, as his name would signify, was very rotund in build, with a rosy face, and a good-natured twinkle in his eyes.

“Yes, only for that they would have commandeered the boxed seaplane long ago, and by now dozens of fleets made on the same model would be pouncing on the German bases along the Belgian coast,” remarked the boy whose name was Frank, and to whom the other two evidently looked up as though he might be their leader in the enterprise requiring skill and courage.

“But they’ve been mighty good to us since then,” went on Pudge. “They have allowed us to have a substantial hangar built after our own peculiar pattern within reach of the water here at Dunkirk, though we are not so many miles away from where the Allies are fighting the Kaiser’s men who are in Belgian trenches.”

“Yes,” added Billy Barnes, who had once been a lively reporter, now a member of the aëroplane manufacturing company engaged in making the remarkable type of airships invented by Pudge’s scientific father, Doctor Perkins, “and during these weeks we’ve been able to get our machine together, so that right now it’s in prime condition for making a flight on the sea or in the air.”

“Whisper that next time, Billy,” cautioned Frank, casting a quick glance about him as the three boys continued to walk along the road leading out of Dunkirk, which in places even skirted the water’s edge.

“Why, what’s up, Frank?” exclaimed the talkative Billy. “Do you think these bushes and trees have ears?”

“No, but there might be some sharp German spy hanging around this place,” replied the other earnestly. “You know they do say they’re everywhere. I’ve heard British soldiers in Calais and Dunkirk tell of mysterious strangers who disappeared when approached as if they were made of smoke. This spy system the Kaiser’s men have down to a fine point. It’s hard to keep anything from being carried to German Headquarters these days.”

“Still, there are a lot of things they haven’t learned before they happened,” declared Billy. “That first British army of some eighty thousand soldiers came over to France, and nobody knew a thing about it until they were on the firing line. But, Frank, do you reckon the Germans have been watching the three of us working here with our hangar and hydro-aëroplane?”

“I’m as sure of it as I am of my own name,” declared the other firmly. “Why, the very fact that our hangar differed so much from ordinary ones, being so much larger for one thing, would make them suspect. Then there has been a heap of talk going on about this wonderful airship of ours, which was carried, every word of it, to German Headquarters.”

“Batter and butterflies!” spluttered Pudge, who seemed addicted to strange exclamations, especially when excited, “we’ll certainly have to watch out, then, now that our wonderful Sea Eagle is in working order.”

“Yes,” said Billy Barnes earnestly, “it would be a tough joke on the company to have some clever thieves get away with it, just when we are ready to show the French Government that it is away above ordinary seaplanes.”

“There’s the hangar, boys,” remarked Frank, with a vein of relief in his voice, as though grave fears may have been giving him more or less uneasiness. “Stir your stumps, Pudge, and we’ll soon be under our own roof. I may have a suggestion to make after we’ve looked around a bit that I hope both of you will agree with.”

While the three chums are advancing on the strangely elevated building that had been erected to accommodate their seaplane, we may take advantage of the opportunity to glance backward a bit, in order to see who and what they were. We do this for the benefit of those readers who may not have had the good fortune to peruse previous volumes in this series.

Two bright, inventive brothers, New York boys, who had actually built an aëroplane which they named the Golden Eagle, had shipped it to Central America when given a chance to save a plantation owned by their father, and threatened by the revolutionists in Nicaragua. This they had managed to accomplish, through the assistance of a young reporter friend named Billy Barnes. In this book, which was called The Boy Aviators in Nicaragua, were also related the thrilling adventures that befell the young air pilots when their craft was carried out to sea in an electrical storm; and also how they were rescued by means of a wireless apparatus through which they communicated with a steamer.

In the second volume, The Boy Aviators on Secret Service, the reader was taken to the mysterious Everglades region of Florida where the young inventors once more demonstrated their ability to grapple with emergencies. They proved that they were patriotic sons of Uncle Sam by discovering and putting out of commission a factory that was making dangerous explosives without the consent of the Washington Government.

It was a long jump from Florida to the depths of the Dark Continent, but the occasion arose necessitating their taking this trip to Africa. If you want to learn how theirs was virtually the first aëroplane to soar above the trackless heart of Africa, how they found the hidden hoard of priceless ivory secreted by slavers in the wonderful Moon Mountains, what strange things came about through their being hunted by the vindictive Arab slave trader, with many other interesting adventures, you can do so by procuring The Boy Aviators in Africa.

Through the coaxing of their warm chum, Billy Barnes, the boys were next induced to enter in a competitive race across the continent, and it can be easily understood that the pages of this book, The Boy Aviators in Record Flight, fairly teem with exciting incidents and thrilling adventures. Crossing the great Western cow country, they met with many difficulties from sand storms to treacherous cowboys and renegade Indians that threatened to end their game voyage. But the same indomitable spirit that had carried Frank and Harry through so many trials allowed them to meet with the glorious success they so richly deserved.

From one series of adventures like this it was easy for the wide-awake young air pilots to engage in others. A story of an old Spanish galleon caught in the grip of that mysterious Sargasso Sea, where the circling tides have held vessels amidst the floating grass for centuries, fascinated them, and they set out to explore the dismal region that has been the graveyard for countless ships. Of course, the lure lay in the fact that a vast treasure was said to be aboard this old galleon; and the hunt for it, together with the opposition caused by a rival expedition, makes great reading for boys who have red blood in their veins. It is all set down in The Boy Aviators’ Treasure Quest, which has been voted one of the best of the entire series.

The Boy Aviators’ Polar Dash was possibly the most remarkable example of Young America’s nerve ever written. How the brothers came to plan the trip to the Antarctic region, and what amazing things happened to them while carrying it out, you will certainly appreciate when you read the book. The object of the expedition was fairly covered, and they came back in safety; but only for the aëroplane the result could never have been attained, which proved how valuable an airship might be amidst the eternal ice of the frozen zones.

In the volume following this, the boys again found themselves caught in a swirl of exciting events. They had become engaged to Doctor Perkins, who was not only a scientific gentleman of note but particularly an aviator bent on startling the world through the agency of a monster seaplane which he had invented. He believed that a voyage across the ocean could easily be made in one of his safe aircraft, which combined many features not as yet in common use among the most advanced aviators. On Brig Island in Casco Bay, within sight of the Maine coast, they erected their factory, and manufactured various types of aëroplanes for the market. So far this wonderful seaplane had not been given to the world, for Doctor Perkins was shrewd enough to first get his patents in all foreign countries in order to protect his interests. In The Boy Aviators’ Flight for a Fortune have been related a series of remarkable adventures that befell the young air pilots when trying out the first of these enormous hydro-aëroplanes, that would skim along the water or sail through the air with equal swiftness and safety.

One of these enormous seaplanes had been boxed in sections and shipped over to France, with the design of giving the Government officials an actual exhibition before they would agree to making a large contract with the firm.

Then the terrible world war had broken out, and for some months it was not known just what had become of the precious machine.

Finally word was received that it was safe at Havre, under the protection of the French Government, which would adhere strictly to the letter of the written agreement which they had entered into with the American company.

An urgent request was sent across the sea for some competent aviators to come over and put the several parts together, so that an actual test could be made. The French Government, if the trial proved convincing, stood ready to make almost any kind of contract with the company. This would be either in the way of ordering a large number of seaplanes, providing they could be delivered without breaking the neutrality laws binding the United States, or else giving a royalty on each and every machine manufactured in France under the patents granted to the doctor.

This necessary but brief explanation puts the reader, who may not have previously known Frank and his chums, in possession of facts concerning their past. While Pudge Perkins, the doctor’s son, was not an experienced aviator, he had picked up more or less general knowledge in the factory, and had come abroad with Frank and Billy, as he was accustomed to say, just to “keep them from dying of the blues, in case the French Government kept putting them off from week to week, or if anything else disagreeable happened.”

Indeed, Pudge, with his abounding good nature, his love for fun, and great capacity for eating, might be looked upon as a pretty fine antidote for the dread disease known as the “blues.” No one could long remain depressed in mind when he was around. Besides, Pudge was really smarter than he looked; appearances in his case were apt to be deceptive; for the boy had a fund of native sagacity back of his jolly ways.

Their hangar had been built in a rather lonely spot close to the water. This was done for several purposes, chief among which might be mentioned their desire to avoid publicity.

The obliging French authorities had even placed a guard at the point where the road passed the open spot now enclosed with a high fence; and so effectual had this proved that up to now the Americans had really not been annoyed to any extent.

Frank, however, had known for some time that all their movements were being watched from different elevated stations in the way of hilltops, or the roofs of houses, by men who carried field glasses. He had many times caught the glint of the sun on the lens when a movement was made.

As long as it went no further than that Frank had not cared, because these suspected spies could see next to nothing. But of late serious fears had begun to annoy him. The seaplane was ready for its first trip, and in a condition where it might be stolen, if a band of daring men took it into their heads to make the attempt.

At one end of the hangar a long track with a gradual slope ran down to the water, so that the seaplane could be launched in that way if desired. A narrow stairway on the land side led up to the stout door which they always kept fastened with an odd padlock capable of resisting considerable pressure.

Each one of the three boys had a key for this lock, which they were very careful to keep fastened to a steel pocket chain. Pudge, having mounted the stair first, puffing from the exertion, was about to insert his key in the padlock when he was heard to utter an exclamation. The others saw him look closely, and then turn upon them with an expression of mingled alarm and consternation on his round face.

“As sure as you live, boys,” the stout boy gasped, “that’s a bit of wax sticking to our padlock! Someone’s been taking an impression so as to have a duplicate key made!”

CHAPTER II.
THE WORK OF GERMAN SPIES.

When that astonishing declaration made by Pudge told the other two boys the nature of his discovery, they also glanced at the suspicious atom of wax sticking to the brass padlock.

“Sure enough, Frank; that it is,” gurgled Billy Barnes.

“There’s no question about it,” admitted Frank, as he took the fragment between his thumb and forefinger, and examined it.

“It wasn’t here when we came around this morning, I’d take my affidavy to that,” declared Billy.

“Dories and dingbats, not a bit of it!” exclaimed Pudge. “That padlock was as clean as a whistle, for I rubbed it with my sleeve to brighten it. There’s been some one snooping around here since then; and I guess they must mean to come back again to-night to steal the seaplane!”

“Open up, and let’s make sure things are all right still,” demanded Frank. “We can settle on some sort of plan to upset their scheme by putting on a new lock, or something like that.”

Pudge, with a trembling hand, managed to insert his key, and upon the door being opened the three boys hurried inside the curious elevated hangar. It had been built with a metal roof, though whether this would really prove bombproof in case of a German air raid, such as had occurred several times, was a question.

“Thank goodness! everything seems to be O. K., boys!” cried Billy, after he had taken a swift survey of the interior, including the monster seaplane built on so advanced a model that there was certainly nothing like it known to aviators.

Frank, too, breathed more freely, for he had not known what to expect.

“Yes,” he went on to say earnestly, “and we ought to be mighty thankful that we’ve managed to get along up to now without having our whole outfit wrecked by a bomb, set on fire by a German spy, or raided some night by a party of unknown persons who would have an interest in keeping the French Government from getting this sample seaplane.”

“My idea is this,” remarked Billy soberly. “They could have done the mischief at almost any time, but some one in authority thought it would be a brighter idea for them to wait until we had finished working on the plane, and then steal it, so that the Germans could copy our model for their army.”

“Gatling guns and grasshoppers, but I think you must be right, Billy,” exploded Pudge. “Haven’t we known that they kept a steady watch on us while we worked away here, even if they couldn’t see much? And many a time we disputed whether those chaps were German spies, or Frenchmen set on guard so as to make sure we didn’t take a notion to fly away some day to the enemy.”

Frank was looking unusually serious, and it could be plainly seen that he had a weight on his mind. The afternoon was near its close; and before long the shadows of a dark February night would be closing in around them.

“One thing sure, boys,” he finally said, “we must not leave our seaplane unguarded another night.”

“Do you think they mean to make away with it tonight, Frank?” demanded Billy.

“In some way they seem to know we’ve finished our work,” came the reply. “It puzzles me to guess how they learned it, when we only this noon notified the French authorities in secret that we were ready for any sort of long-distance test they might wish to order.”

“Must be a leak at Headquarters!” suggested Billy quickly.

“Tamales and terrapins, that would be a nice proposition, I should think!” ejaculated Pudge.

“Let’s step out and look around a little,” suggested Frank. “Perhaps we may find some trace of these unwelcome visitors who have managed to get up here to our door in spite of the soldier standing guard by the gate of our stockade.”

“They must have come from the water side, Frank,” Pudge was heard to say as he followed the others down the stairway that led to the ground.

“Be careful how you step around,” cautioned Frank. “Here, both of you plant a foot alongside mine, and in that way we’ll have a set of prints to go by. Now notice just what they look like, and see if you can find any fresh marks that are different in some way from ours.”

It was an easy task he had set them, for almost immediately Billy sang out to the effect that he had made a discovery, and hardly had he ceased speaking when Pudge announced that he, too, wanted Frank’s opinion on a footprint that was much too large to have been made by any of them.

A further hunt revealed the fact that apparently three parties must have been at the foot of the steps leading up to their locked hangar. This important discovery was anything but pleasant to Frank Chester; it told him that a crisis was undoubtedly approaching their enterprise, which would seriously affect its success or failure.

What if, after all their earnest work, just when the wonderful seaplane had been made ready for a flight, those secret emissaries of the Germans managed to steal it away! Doubtless they had prepared for just such a stroke, and had an experienced air pilot hovering around so as to take charge of the hydro-aëroplane after it was successfully launched.

That would be the last the aëroplane boys would ever see of their valuable property. In time of war all devices are recognized as proper, and this theft of the American seaplane would be hailed as one of the most glorious feats of the German arms, as well as a serious blow at the air power of the Allies.

“There’s only one thing to be done,” said Frank, turning to the stout chum, “if you are game to tackle it, Pudge.”

The fat boy winced but set his teeth hard together.

“Rifles and rattlesnakes, just try me, Frank, that’s all!” he chortled, squaring his shoulders aggressively in a manner the others both knew meant that his fighting blood had been aroused.

“While Billy and I stay here to guard the machine, you must go back to town and get another kind of padlock, Pudge!” exclaimed Frank. “Pick out one that will hold as securely as this does. If we have to change it every day, we’ve got to make a sure thing of it.”

“Was it that you said you meant to speak about after we got inside the hangar, Frank?” inquired Billy as Pudge prepared to start bravely away through the gathering shadows of evening.

“Well, it was something along the same lines,” explained Frank; “in fact, I meant to suggest that one of us stay here nights until we had word from Headquarters that the hour had come to make our test, and prove that the Sea Eagle could stand up against a gale when common seaplanes would go to smash, or have to stay at their moorings.”

“Mumps and mathematics, but I agree with you there, Frank!” cried Pudge. “And for one I’m in favor of camping out here right along. We could rig up a little stove, and cook our meals. It would be good fun at that, because then we’d have the real old-fashioned Yankee grub instead of this French fool stuff that never satisfies a healthy appetite.”

The others looked at Pudge and exchanged nods. They knew his failing, and could sympathize with the poor fellow. Pudge was patriotic enough to prefer the American style of cooking, which always spelled abundance according to his way of thinking.

“I’m off, fellows,” he now announced. “Look for me inside of an hour or so. Of course, it’ll be about dark by then, but I know every stone on the road between here and town, I’ve traveled along the way so often. So long!”

With a genial wave of his hand, Pudge left them. The other pair looked after him with considerable solicitude; there was only one Pudge after all, according to their opinion, and he had a happy faculty for wrapping himself in the affections of his mates.

“You don’t think anything could happen to him going or coming, do you, Frank?” asked Billy Barnes, as they saw Pudge vanish through the partly open gate of the high stockade.

“Why, no; I hardly think so,” replied the other slowly. “Perhaps I should have gone for the padlock myself. If I had thought twice, I would have done that.”

“Too late—Pudge is on the way,” remarked Billy. “Let’s go up and take a peep around once more to see that everything is in apple-pie shape—each wire-stay keyed up to the right tune for efficiency, the motors ready to do business, the gas pump lubricated, and, in fact, our machine fit to toe the scratch as if there were a race on.”

Once they were inside the hangar, Frank fastened the door with a bar that had been arranged for just such a purpose. Then, turning on a flood of light from an acetylene gas battery, they examined every part of the big seaplane. It had something of the appearance of a gigantic sleeping bat as it lay there motionless, but with all the attributes of tremendous power for skimming along on the surface of the water or soaring among the clouds.

“In perfect condition, as far as I can make out!” remarked Frank, after they had completed this careful survey.

“Yes,” added the other, with a glow of excusable enthusiasm on his face, “and if there was any necessity for doing it we could be off with a minute’s notice.”

“I took pains to make sure that there was a clear and uninterrupted stretch of water in front of our hangar,” said Frank. “No vessels are allowed to anchor on this side of the harbor, though there are many transports from Great Britain across the way that have brought men and war material and stores over.”

“Oughtn’t Pudge be about due by now, Frank? It’s pitch dark outside, and I should think a full hour must have crept by since he left us?”

“I was thinking of that myself, Billy. Still, we must remember that our chum is a bit slow on his legs, compared with the way you and I get over the ground. Besides, he may have been delayed at the store where he expects to get the new padlock.”

“Yes, I hadn’t thought of that,” admitted Billy. “But we might use the ’phone we have installed, and find out if he’s started back. It would make our minds a little more easy, you know.”

“Just as you say, Billy. And suppose you call them up while I do something I want to alter here—nothing of consequence, of course, but the change would strike my eye better.”

“All right, Frank.” With which remark Billy turned to one end of the hangar close by, where a telephone apparatus could be seen attached to the wooden wall.

Frank went at his little task with his customary vim. It mattered nothing to him that the flight of the great seaplane would be neither hindered nor assisted by its consummation. He simply liked to see things shipshape at all times.

“What’s the matter, Billy?” he called out presently, on hearing the other ring for the third time, and also muttering to himself as though annoyed.

“Why, Frank, I don’t seem able to get Central,” replied Billy, once more energetically working the handle of the apparatus.

Apparently Frank was enough interested to cross over so as to see for himself what was wrong. He sat down on the box Billy vacated and tried to get in touch with the operator at the central switchboard. After testing it in several ways, Frank replaced the receiver and looked up at his chum.

“Have they disconnected our wire at Central, do you think, Frank; or is the hello girl flirting with her beau, and not paying attention to business?” asked Billy.

“Neither,” answered the other soberly; “but I’m afraid somebody has cut our wire so as to keep us from calling for help if anything happens here to-night!”

CHAPTER III.
SAVING THE GREAT SEAPLANE.

“Gee whillikins! that sounds like a serious proposition, Frank!” exclaimed Billy Barnes, when he heard the opinion of his companion.

“It looks as though we’re up against something,” admitted the other grimly. “They’ve evidently set out to capture this seaplane, and mean to do it, no matter at what cost.”

“A compliment from the Kaiser to the ingenuity of Yankee inventors, I’d call it,” said Billy; “but all the same I don’t feel like throwing up my hands and letting them raid our shop here. It’s a good thing we made that discovery, thanks to Pudge and his sharp eyes.”

“Yes, and that you thought to use the wire, which showed us how somebody had been meddling so as to cut us off from the city,” Frank remarked.

“What if they come in force, knowing we’re here, Frank?”

“That door would not be able to stand much of an attack if they carried axes along with them, I’m afraid,” Billy was told.

“My stars! do you think they’d be apt to do that sort of thing?” demanded the astonished assistant, as he looked around for some sort of weapon with which he might defend the passage of the doorway, should it come to a question of fighting.

“If they want this plane as badly as we think they do,” said Frank, “there is little that desperate men might attempt that they would not try.”

“And still there’s no sign of poor Pudge!” ventured Billy, putting considerable emphasis on the adjective, as though he could almost imagine the happy-go-lucky Pudge lying on his back somewhere along the road, groaning in pain after having been struck down by a cowardly blow.

“I’m sorry to agree with you,” Frank admitted slowly, “but at the worst we’ll hope they’re only detaining our chum, and that he hasn’t been hurt.”

“How about my slipping out and trying to go for help, Frank? If they only knew at Headquarters about this, they would send a whole regiment of British Tommies on the run to patrol our works here. Say the word and I’m off.”

Frank, however, shook his head as though the idea did not appeal to him.

“The chances are they would be on the lookout for something like that, Billy.”

“And lay for me, you mean, don’t you, Frank? Well, then, if it wasn’t so cold I’d propose slipping down to the water and doing a little swimming stunt. Too bad we didn’t think to have a boat of some kind with us.”

“I was just thinking,” ventured Frank, “that only on account of our being rushed for time we would have installed a wireless plant here, as we’ve often done before. Then we could send all the messages we wanted, and these spies wouldn’t be able to bother with them.”

“Yes, if we had only thought we’d run against a snag like this, Frank, we could have done that as easy as falling off a log. But it’s too late now to bother. The question is, what can we do about it?”

“There’s always one last resort that I know of, Billy.”

“Glad to know it, but please inform me as to its nature, won’t you, Frank? I would give half of my year’s salary just to be able to snap my fingers in the faces of these smart secret agents of the envious Germans who want to steal our thunder.”

Frank turned and pointed straight at the big seaplane.

“There’s the answer, Billy!” he said shortly.

At first the other simply stared as though unable to grasp the meaning of Frank’s words. Then a sudden gleam of gathering intelligence began to show itself in his eyes; he emphatically brought down his fist in the open palm of his other hand.

“Wow! that’s sure the ticket, Frank!” he burst out with, his enthusiasm spreading until his face was one solid grin. “We’ve got a way of escape right in our grip, and I was so blind as not to see it. Run off in the plane, of course, and leave the smarties to bite their fingernails. Great head, Frank! These German spies may think themselves wide-awake, but they’ll have to get up bright and early in the morning to catch two Yankee boys napping, believe me!”

“Listen, Billy!”

“Did you think you heard something then, Frank?”

“There’s someone at the door yonder; I saw it move, but the bar kept it from giving way,” Frank went on in a low tone. “Don’t act as though you suspected anything out of the way. They may be watching us through some peep-holes that have been bored in the walls. It would be foolish for us to give our plan away.”

“I understand what you are aiming at, Frank,” remarked the other, trying hard to appear perfectly natural, immediately adding under his breath: “There, I saw the door quiver again. They must wonder why it refuses to give way. That bar is our salvation, because like as not there’s a number of them out there who would flock in with all sorts of weapons, meaning to keep us quiet while their aviators examine the machine and get ready for a launching. Whee! then good-by to our bully Sea Eagle forever.”

“That’ll never happen as long as we can lift a hand to prevent it,” said Frank.

“Say, you don’t think that could be Pudge trying the door?” suggested Billy, as though struck by a sudden bright idea.

“Not very likely,” came the reply; “but we can easily tell. If he hears me give our old signal, Pudge will answer on the dot. Listen and see if anything comes of it.”

The whistle Frank emitted was of a peculiar character. It was immediately imitated from without, and so exactly that one might think it an echo. Frank shook his head on hearing this.

“Pudge isn’t there,” he said decisively. “If he was, as you very well know, Billy, he would have sent back the other call, entirely different from the one I gave.”

“Then some fellow answered for Pudge, thinking we might open up, when they could rush the place and get possession—is that the way it stands, Frank?”

“As near as I can make out, it covers the ground,” the young air pilot replied. “Now I’m going to put out this light. We don’t really need it any longer, and if they are watching us through any peep-holes, it would give our plan away.”

“We ought to know every part of this coop, Frank. As for the machine itself, I warrant you could find any stay or guy while it’s pitch dark. Let it go. There, they are trying the door again. Seems as if they can’t understand why it doesn’t give way. If it keeps on shutting them out, sooner or later they’ll try to batter it down. Oh! if I only had a gun here.”

“I intended having one with the seaplane, but thought I wouldn’t bother until we meant to start on a trip,” explained Frank, keen regret in his voice.

“Seems to me it’s always the unexpected that keeps cropping up with us,” complained Billy. “I can look back to lots of times when things happened just as suddenly and without warning as this has.”

“But they didn’t down us, you want to remember,” advised the other, in that confident way of his that always made his chums feel so much better.

“Now they’re starting to pry at the doors, Frank, which means business. Hadn’t we better be getting ready to make a start?”

“First of all I want you to stand by, and when I give the word fling both the large doors wide open,” Frank told him. “After that, as I switch on the searchlight, so as to see what lies ahead, climb aboard to your regular place. And, Billy, please don’t have any hitch in the program if you can help it!”

“Depend on me, Frank,” said the other, slipping away in the darkness that now filled the interior of the big hangar.

Frank mounted to his seat. As no flight of consequence was intended, he did not bother donning the head shield he always carried with the machine, his gloves alone being deemed necessary for the occasion, though both of them had wisely secured their fleece-lined leather jackets. Just as Billy had said, Frank was so familiar with every lever and stay, as well as with the engine, that, with his eyes blindfolded, he could have manipulated the intricate working parts.

Quickly he adjusted things to his liking with a deftness that left nothing to be desired. The fact that those unseen parties on the other side of the door were becoming more insistent with every passing second did not seem to disturb Frank at all; for he knew very well they could not stop his departure now.

When, presently, he had finished his simple preparations and everything was ready for the grand finale, he gave the signal that Billy was expectantly awaiting.

“Open up, Billy!”

Immediately both wide doors flew back, for the boys had arranged things so that it required but a simple movement to accomplish this. Then Billy hustled toward the seaplane, which no longer stood there like a black shadow; for Frank had, with the pressure of his finger, caused the powerful searchlight placed in the bow of the remarkable craft to flood the space in front of the hangar down to and out on the water of the harbor.

Billy swung himself aboard almost in the twinkling of an eye. Then a lever was manipulated and with a rush the monster seaplane started. Even as it left the shelter of the building, Billy, hanging on with nervous hands, could see several figures in the dazzling flood of white light spring wildly aside so as to avoid being crushed by the oncoming giant seaplane as it tore down the inclined track leading to the water.

CHAPTER IV.
THE ESCAPE.

Ahead of them lay that track of dazzling light. Every fragment of timber used in the construction of the inclined trestle upon which the seaplane was expected to reach the water was as plainly visible as at midday, with the sun shining above.

Billy fairly held his breath in fear lest the swift rush of the hydro-aëroplane should catch the two men on the slope unprepared, and hurl them into space. Just in the nick of time they threw themselves to one side, and the plunging monster glided by, so close that had he so willed, Billy could have thrust out a hand and touched one of the shrinking figures.

Then came a tremendous splash as they struck the water. Frank had made his calculations so carefully that there was not the slightest danger of a mishap. The boat was descending at such an angle that it instantly shot off the wheels that were underneath, and skimmed along the surface of the water like a great duck.

Billy drew his breath again, for it seemed as though they had actually run the gauntlet in safety. He heard the familiar throb of the reliable motors beginning to take up their sweet song, which told that Frank had started the machinery at the proper second, so that they did not lose any of the impetus gained in that rush down the slope.

From up in the quarter where they knew the hangar must be, came loud cries of anger. Those who had planned to capture the seaplane when it was in prime condition for a flight to the German lines had evidently met with a most aggravating disappointment.

Suddenly the brilliant light vanished, shutting them in a pall of darkness that was all the more dense because of their having been staring into that illuminated avenue ahead, along which the seaplane was rushing at fair speed.

“It’s all clear in front, Billy,” Frank hastened to say, knowing that his companion must naturally think of the danger of a collision the first thing.

“Listen to ’em growl!” chuckled Billy, who had evidently been greatly amused as well as interested in the remarkable dash of the Sea Eagle. “But, after all, that was what I’d call a close shave, Frank. Didn’t you hear the door being smashed in as we started?”

“I thought I did,” replied the other, “but I knew that nothing up there could give us any trouble. The only chance of our being wrecked was for those on the inclined plane to place some obstruction on the track that would throw the wheels of our carriage off, and dump us in a heap below.”

“They didn’t want to wreck the seaplane, which was what saved us from that smashup,” ventured Billy, and then quickly adding: “Hello! shut her off, did you, Frank?”

The musical hum of the twin motors and the whir of the revolving propellers had suddenly ceased, though the boat still continued to move along the top of the little waves coming in from the Channel.

“Yes, we have gone far enough for the present,” replied the pilot.

They sat there for a little while, listening to the various sounds that reached their ears from the shore. Not far away the lights of Dunkirk could be seen, though these were by no means as brilliant as they might have been before the war broke out. This was on account of the fact that at any hour a raid from German aëroplanes might be expected in and around the encampment of the British troops.

“This is about the queerest situation we’ve ever found ourselves in, Frank,” ventured Billy presently, as he felt the boat moving up and down gently on the bosom of the sea. “It’s an experience we’ll never forget. I’m wondering what the next move on the program is going to be? How can we get ashore tonight in this terrible darkness?”

“We may make up our minds not to try it,” Frank told him quietly, as though he had some sort of plan in his mind, hatched on the spur of the moment.

“What’s the idea, Frank?” asked Billy eagerly. “No matter how you figure it I’m game to stand by you.”

“I’d never question that, Billy,” declared the other warmly. “You’ve proved your grit many a time in the past. But here’s the way the case stands. We could make an ascent from the water if we wanted, but on such a pitch-dark night that would mean trouble about coming down again. So what’s to hinder our staying here until morning—lying on the water like a duck?”

“If the wind doesn’t come up with the change in the tide, we could do it as easy as anything,” assented Billy. “She rides like a duck, and could stand a lot more rough water than we’re getting now. Frank, let’s call it a go.”

“We will find it pretty cold, of course, you understand, Billy?”

“Shucks! haven’t we got on our leather jackets that are lined with fleece that have given us solid comfort many a time when we were six thousand feet and more up in the cold air? Why, Frank, we can strap ourselves to our seats, you know, and one of us can get a few winks of sleep while the other watches, ready to switch on the searchlight if anything threatens.”

“It’s plain to be seen that you’re set on trying a night of it,” said Frank, no doubt well pleased to have it so. “I’m worrying more about Pudge than of myself. Wish we knew he was all right.”

“The same here,” said Billy. “Frank, we must keep listening all through the night to catch his signal, if ever he makes it. You know we’ve got that code for communicating by means of fish horns. If Pudge gets to the hangar and finds that we’re not around, the first thing he’ll think will be that the seaplane has been stolen.”

“Unless,” Frank hastily interrupted, “he happened to be near enough to hear something of the row, when he ought to be able to guess what really happened. In that case I expect that later on, when he thinks the coast may be clear, Pudge will try to communicate with us. As you say, we must keep on the alert. If you hear a sound that comes stealing from far away on the shore and resembles the bawl of a bull, answer it. Pudge will be in a stew about us, of course.”

They sat there for some time listening, and exchanging occasional remarks. Then, at Billy’s suggestion, they made use of the stout straps that were attached to each seat, intended to enable the navigators of the air to reduce to a minimum the risk of falling from a dizzy height.

“Take your choice, Frank, first watch or second,” was the next proposition advanced by the one-time reporter. “I’m used to be up at all hours of the night—that was my busy time on the paper. So turn in, and I’ll take charge of the deck.”

“It’ll only be a cat nap then, Billy,” said the other, settling himself as comfortably as the conditions allowed, which was not saying much. “See that bright star over there in the west; it will drop behind the horizon in about an hour or so. Shake me then if I happen to be asleep.”

“All right, Frank. And if anything crops up in the meantime that bothers me, I’m going to disturb you in a hurry.”

“I hope you will, Billy; we can’t afford to take any chances, understand, for the sake of a little sleep. Listen for signs of Pudge. It would relieve me a whole lot if I knew that he was safe.”

After that Billy sat there and kept watch. The buoyant craft that had been so cleverly constructed so as to be equally at home on the water or in the air, rode the lazy billows that came rolling in from the Channel. The only sounds Billy could hear close by were the constant lapping of the waves against the side of the craft; though further off, toward the city, there was a half subdued murmur, such as might accompany the gathering of thousands of men in camp.

The lights had almost wholly vanished by this time, showing the strict discipline that was in vogue in these stirring times. Frequently had daring German aviators appeared above Dunkirk to drop their bombs in the endeavor to damage the congested stores of the British troops, or strike a note of terror among the inhabitants of the Channel city.

Billy every little while twisted his head around and looked in different directions. But thick darkness lay about the floating seaplane, utterly concealing the shore as well as all vessels that lay further along in the harbor.

Possibly half an hour had passed in this way when Billy felt a sudden thrill. He started up, straining his hearing, as though to catch the repetition of some sound he believed he had heard.

Then, leaning over, he shook Frank.

“It’s Pudge signaling, Frank, or else I’m away off my base. Listen!” was what he told the other, in excited tones.

A minute later and they both caught the far-away sound of what seemed to be the winding blast of an Alpine hunter’s horn.

“Yes, it’s Pudge, all right, and he wants to hear from us if we’re within reach of the sound of his signal. Answer him, Billy!”

Already Billy had taken the horn from its fastenings, and no sooner had Frank given the order than he applied it to his lips. The sound that went forth, coming as it did from the blackness of the sea beyond, must have astonished any sailor on board the various steamers in the harbor.

Once, twice, three times did Billy give the peculiar note that Pudge knew so well. It must tell the absent chum that they were safe, and in the language of their secret code ask how things were going with him.

“There, he’s given us back the message word for word!” cried Billy, as they caught the faint but positive reply from the unseen shore, perhaps at the deserted hangar. “Frank, he’s all right! That takes a big load off our minds.”

“Yes, now I can rest easy!” declared the other. “As that star isn’t close to the sea as yet, Billy, if you don’t mind, I think I’ll try for a few more winks of sleep. Pudge will go back to town and stay at our lodgings until we turn up, or send him a message. Everything is working finely.”

“For us,” added Billy, chuckling. “But think how mad those spies must be over losing the prize they thought was sure to fall into their hands. Why, I wouldn’t be surprised if they discounted the capture of our seaplane, and over in Belgium were ready to start to work making copies of the same as soon as the sample could be delivered.”

Billy appeared to be highly amused, for he chuckled to himself for several minutes while picturing the disappointment of the baffled plotters. Then once more he settled down to his task of serving as “officer of the watch.”

As the minutes crept on, Billy began to observe the gradual approach of the star to the vague region where sea and heavens merged in one. In fact, Billy was yawning quite frequently now. He found himself fairly comfortable, thanks to the warmth of that leather fleece-lined jacket, and the hood which he had drawn partly over his head. Still, it was not very delightful, sitting there on the water; and perhaps the boy’s thoughts frequently turned toward the bed he was missing.

“I wonder which way we’re drifting now?” he suddenly asked himself; he immediately set to work trying to answer his question by observing the direction of the tide, as well as by the light current of air.

When next he thought to turn his head so as to glance backward, Billy received a bit of a shock. A sort of thin haze had settled down on the water by now, but through this he had discovered two moving lights. They looked very queer as seen in that foggy atmosphere; but Billy was smart enough to know what they stood for.

He immediately awoke Frank, whispering the astonishing news in his ear.

CHAPTER V.
A NIGHT ON THE CHANNEL.

“They’re looking for us, and they’ve got lanterns, Frank!” was what the one on guard said in a low tone as he pulled his chum’s sleeve.

Frank was wide-awake instantly, and one quick glance showed him the approaching peril.

“Yes, you’re right about it, Billy,” he observed cautiously, and if there was a little quiver to his voice that was no more than might be expected under the exciting conditions by which they were surrounded.

“How queer the lights look swinging along close to the water, and in that fog, too. They are heading out this way, I’m afraid, Frank.”

“It seems so, Billy.”

“Hadn’t we better get under way, then?” continued the nervous one.

“No hurry,” Frank told him. “They may happen to swing around one way or the other and miss us. We’ll wait and find out. You know we can get moving with a second’s warning. Now let’s watch and see what happens.”

Billy could be heard sighing every now and then. Doubtless, as he sat there with his head turned halfway around, observing the creeping movements of those two strange lights through the fog that hugged the surface of the water, he was thinking it the most exciting moment of his whole career.

Then a new idea seemed to have lodged in his brain, for again he whispered to his companion.

“There may be more than those two boats, Frank!”

“Possible but not probable,” Frank replied.

“What if, when we started off with a rush, one happened to get in the way?” pursued Billy.

“I’d be sorry for the men in that boat, that’s all, Billy!” was the laconic reply he received, and apparently it satisfied the other, for he did not pursue the subject any further.

Meanwhile it became apparent that the searching boats were gradually drawing nearer the floating seaplane. Unless they changed their course very soon those in the hostile craft would be likely to make a discovery that must fill them with delight.

“Are we headed right for a start, Frank?” asked Billy, a minute later.

Frank himself had been considering that very thing. The influence of the tide seemed to have swung the seaplane around a little more than he liked; but then this could be easily remedied, for they were prepared for such a possibility when on the water.

There was a little paddle within reach of Frank’s hand; all he had to do was to pull a couple of cords, and it was in his possession.

Softly he worked it through the water. Frank had spent many happy hours in a canoe when on his outing trips, and knew how to wield a paddle like an expert. He had even taken lessons from one of those old-time guides accustomed, in years gone by, to using a birch bark canoe in stealing up on deer when jacklight hunting was not banned by the law.

Consequently he now used his paddle without making the slightest noise; and under its magic influence the clumsy craft gradually veered until he had its spoon-shaped bow heading just where he wanted it. Then he handed the paddle to Billy to replace as best he might.

They could by this time vaguely make out the nearer boat, and also the indistinct figures of two men. One of these was rowing, while the other held up the lantern.

Of course, there was nothing to tell Frank who they might be. Perhaps, in these stirring times, the waters of the harbor had to be patrolled by guards on the watch for submarines or other perils. These protectors of shipping may have heard or seen enough that was suspicious to warrant a search of the adjacent waters.

He was more inclined to believe, however, that the German spies, rendered furious by the escape of the coveted American seaplane had, as a last resort, started out to scour the water nearby in hopes of locating it.

“Frank!” whispered Billy again, “I think he glimpses the seaplane through the fog!”

The actions of the man holding the lantern indicated this, for he was plainly much excited, turning to his companion at the oars as though urging him to make more haste.

“Then it’s high time we were off!” said Frank.

Again did Billy hold his breath as the possibility of the motors failing them in this great emergency flashed through his mind. But he need not have allowed himself this mental anxiety, for no such calamity befell them.

A shrill whistle was heard, evidently a signal to those in the second boat to inform them that the object of their search had been discovered. Then came the cheery whirr of the motors, accompanied by the churn of the busy propellers, and like a giant, double-winged dragonfly, the seaplane started along the surface of the water, followed by another burst of angry shouts.

“Duck! they may be going to shoot!” exclaimed Frank, suiting his actions to his own words.

That was just what did happen, for a volley of shots sounded, and had the motors not been making so much noise the boys might have heard the whistle of the passing leaden messengers.

There was no harm done, for, unable to longer see the speeding seaplane, those who used their weapons with such reckless abandon had to fire at random. Skimming the water like an aquatic bird, with a gradual but rapid increase to their speed, the seaplane soon began to rise.

Billy realized from that that Frank meant to make an ascension, possibly deeming it wise to get away from such a dangerous neighborhood as quickly as possible. And, as they anticipated, the reliable Sea Eagle was doing her prettiest when called upon to show her fine points.

Once free from the sea, they rose until Frank felt sure of his position. He had switched on the electric searchlight, and the storage battery was of sufficient power to send the ray of white light far ahead. It could be turned to any quarter of the compass.

“Well, here we are off on our trial trip sooner than we expected,” said Billy, meaning to draw the other out, for he was consumed by curiosity to know what was coming next.

“Two narrow squeaks on one night ought to be enough, don’t you think, Billy?” asked the pilot, as he started out into that avenue of light, and then glanced at the handy compass so as to fix their course on his mind.

“Well, we’ve been pretty lucky so far,” admitted the other. “It wouldn’t pay to keep up that sort of racket. They say, you know, that the pitcher may go to the well just once too often. It might be three times and out for us.”

“And neither of us feels like accommodating those anxious German secret agents whose one business in Dunkirk is to steal our thunder, do we, Billy?”

“Not much,” replied the other boy with decided emphasis. “I’d sooner see the airship smashed to pieces than know it had fallen into the hands of the Kaiser’s men.”

“Hold on, Billy! You know we’re supposed to be neutral in this fighting business. We’ve got some mighty good friends who are of German blood, and we think a whole lot of them, too.”

“Oh! I’m not saying a word against Germans; they’re as fine a people as any in all the world; but, Frank, what we’ve met with in Northern France and in the little of Belgium we saw that day Major Nixon took us out in his motor car, somehow set me against the invaders. Anyway, we’ve been treated splendidly by the French here, and our business has been with them.”

“That’s understood, Billy, and I agree with you in all you say. But let’s talk now about our chances of dropping down again to the water.”

“Oh! then you don’t mean to stay up here, Frank? Will it be safe to descend, do you think?” asked Billy, a new sense of anxiety gripping him.

“So far as the plane is concerned we can do almost anything with it,” Frank assured him. “Our light will tell us whether the sea is too rough for alighting. We’re heading downward as it is right now. Steady, Billy, and keep on the watch.”

Having taken his course, Frank knew that they must be out on the channel some miles from the harbor. On nine nights out of ten he would have hesitated about attempting such a risky proceeding as he now had in view; but the calmness that prevailed encouraged him to take the chances of a descent in the darkness.

“I can see the water all right, Frank!” exclaimed Billy a minute later, as the wonderful air and water craft continued to head downward, though with but a gradual descent.

“It looks good to me,” ventured the pilot, with confidence in his tone.

Presently they were so close to the surface of the water that both of the boys could see that it was fairly quiet. The long rollers were steadily moving toward the southeast, as though the night air influenced them, but then Frank had before now dropped down on the sea when it was much more boisterous.

“Here goes!” he remarked, as he deflected the rudder just a trifle more, and immediately they struck the water.

The Sea Eagle, being especially constructed for this sort of work, and having a spoon bow that would not allow her to dip deeply, started along on the surface, with the motors working at almost their lightest speed. Then Frank cut off all power.

“We did it handsomely, Frank!” exulted Billy Barnes, feeling quite relieved now that the seaplane had proven fit and right for the business it had been built to demonstrate.

“And here we are floating again,” said Frank, “but this time so far away from the harbor of Dunkirk that there’s no longer any danger from spies. Billy, since that star has dipped behind the horizon, suppose you take your little twenty winks of sleep.”

“You think it’s perfectly safe to lie here the rest of the night, do you, Frank?”

“Why not, when we can get away if the wind should come up, and the sea prove too rough for us? Make your mind easy on that score, Billy.”

“But how about steamers crossing from the other side of the channel?” asked Billy. “I think I heard that they generally take the night to make the trip these times, so as to keep the German aviators from learning how many transports loaded with troops come over. Besides, they avoid danger from submarines, and bombs dropped from Zeppelins that way.”

“Oh! the chances of our being run down are so small that we needn’t bother about them,” Frank assured the nervous chum. “I promise you that if I see a moving light, or hear the propeller of a steamer, I’ll wake you up, and we can stand by, ready to go aloft in case the worst threatens.”

That seemed to appease Billy, for he gave a satisfied grunt and proceeded to settle himself for a nap.

“This is being ‘rocked in the cradle of the deep,’ all right,” he remarked, as the floating seaplane rose and fell on the swell. Frank made no reply, so that presently Billy relapsed into silence, his regular breathing telling the other he was sound asleep.

So the long night crept on. The boys managed to catch more or less sleep, for nothing arose to alarm them. Naturally, their position was far from a comfortable one, and therefore Frank, who happened to be on duty at the time, felt pleased more than words could tell when he eventually glimpsed a light in the eastern sky that proclaimed the coming of dawn.

CHAPTER VI.
UNDER SHRAPNEL FIRE.

“Have we anything to eat along with us, Frank?”

“Why, hello! are you awake, Billy? I was just thinking of calling you, or sending a bell hop up to pound on your door. It’s morning, you see.”

“Yes, I noticed that light over there in the east, and was thinking how the poor fellows in the trenches must feel when they see it creeping on, knowing as they do that it means another day of hard work and fighting. But how about my question, Frank? Did we think to fetch that pouch of ship-biscuit along with us?”

“Yes, it’s tied just back of you,” the other informed him with a laugh. “But I’m surprised to hear you so keen for a bite, Billy. If it had been Pudge, now, I wouldn’t have thought so much about it, because he’s always ready for six meals a day.”

“I don’t know what ails me,” acknowledged the other, as he reached for the little waterproof bag in which Frank always tried to keep a pound or so of hardtack, with some cheese as well, to provide for any emergency like the present, “it may be this sea air, or perhaps it’s due to the excitement we’ve gone through; but I’m as hungry as a wolf in winter.”

“Perhaps I may take your appetite away then,” suggested Frank, with a chuckle.

“In what way?” demanded Billy, with a round ship biscuit halfway to his mouth.

“Oh! by making a stunning proposition I’ve been considering while I sat here, that’s all.”

“Gee! it takes you to think up things, Frank. Now, as for me, I’ve been badgering my poor brains about how we would astonish the people of Dunkirk when we came sailing into the harbor and made for our hangar. There’d be as much excitement as if a dozen of those little Taube aëroplanes of the Germans had hove in sight, just as they did on that day of the last air raid. Now tell me what the game is, please, Frank.”

“Suppose, then, we weren’t in such a big hurry to go back to our moorings?” said the other. “Suppose, that having broken away, we took that trial spin we’ve always been promising ourselves when things were ready!”

Billy became so excited that he actually forgot to eat.

“Wow! that’s a brilliant scheme, Frank, let me tell you!” he exclaimed. “Say, for a wonder, all the conditions favor aëroplane work. The wind that has kept up during the last three days seems to have blown itself out, and we’re likely to have a quiet spell. They’ll be on the watch for another raid of those Taubes from up Antwerp way on such a calm day as this. Frank, shall we try it?”

“Wait for another half hour,” replied the other. “By then it will be broad daylight, and we can see what the signs promise. If things look good we’ll start up and take a run to the northeast.”

“Over the trenches, do you mean, and perhaps far into Belgium?” cried Billy, to whom the prospect of seeing something of the terrible fighting that was daily taking place in the lowlands along the canal appealed with irresistible force; for the old reporter spirit had never been killed when he gave up newspaper work for aëroplane building.

“We’ll see how the land lies,” was all Frank would say. Billy knew very well the other was bound to be just as keenly interested in the warlike scenes below them as he could be, hence he was willing to check his impatience, leaving everything to Frank.

Both of them munched away on the ship-biscuit and cheese. It was pretty dry fare, but then there was a bottle of water at hand if they felt choking at any time.

The half hour passed and they could see from the growing light in the eastern sky that the sun would soon be making its appearance. Around them there was nothing but an endless succession of rollers, upon which the buoyant seaplane rose and fell with a continual gurgling sound.

“If this low-hanging fog would only lift,” remarked Billy, as he put away the hardtack bags, “we could tell just where we were. As it is, there’s no such thing as seeing land, which must be over there to the east.”

“The sea fog is rising and will disappear as soon as the breeze comes,” Frank observed sagaciously. “By then we want to be several thousand feet up, and taking a look through the glasses at the picture we’ll have spread out below us.”

“Let’s start now,” suggested Billy. “I’m wild to see what the country up across the border of Belgium looks like. To think of us being able to glimpse all the German defenses as we go sailing over so smoothly.”

Frank laughed.

“You are counting your chickens again before they’re hatched, Billy, an old failing of yours. It may not be the smooth sailing you think. Remember that the Germans are always ready-primed with their wonderful anti-aëroplane guns for hostile raiders. We may have a dozen Taubes, too, buzzing after us, or find ourselves chased into the clouds by a big Zeppelin.”

If Frank thought to alarm Billy by saying this, he immediately saw that he had failed to shake the other’s nerve.

“Gee! that would make it interesting, for a fact!” the other exclaimed, his face beaming with eagerness. “Frank, you can take my word for it, no Taube, or Zeppelin either, for that matter, can catch up with our good old Sea Eagle, once you crack on all of her two thousand revolutions a minute with both motors. They haven’t got a thing over on this side of the big pond that is in the same class with Doctor Perkins’s invention.”

“I think you’re pretty near right there, Billy,” said the pilot, as he proceeded to press the button that would start things humming.

Immediately they were beginning to move along on the surface, the peculiar spoon-shaped bow preventing the water from coming aboard. Faster went the huge seaplane as Frank gave increased power, until when he tilted the ascending rudder they left the water just as a frightened duck does after attaining sufficient momentum.

“Hurrah!” exclaimed the delighted Billy, as soon as he realized, from the change in motion, that they no longer rested on the water, but were cleaving the air.

Mounting in spirals, as usual, the two boys soon began to have a splendid view, not only of the sea, but of the nearby land as well.

“Oh! look, Frank, over there in the west; those must be the famous white chalk cliffs of Dover across the channel we see. To think that we are looking down at France, and even Belgium, and on England at the same time.”

“That’s about where the Kaiser is aiming to throw those monster shells from his big forty-two centimeter guns, after he has captured Calais, you know,” remarked Frank.

“I guess that dream’s been smashed by now, and there’s nothing in it,” Billy was saying. “Not that the Germans didn’t try mighty hard to get there, and tens of thousands of their brave fellows gave up their lives to carry out a whim of the commander, which might not have amounted to much, after all. Oh! Frank, with the glass here I can see our hangar as easy as anything.”

“That’s good, Billy. I was just going to ask you to look and see if those disappointed spies had done anything to it. I’m glad to hear you say it’s still there in good shape. I expect we’ll have more or less need of that shed from time to time.”

“Well, we don’t mean to spend many nights paddling around on the sea,” affirmed Billy, now beginning to turn his glass upon the country they were approaching, and which lay to the north of Dunkirk.

Frank had changed their course so that they were now over the land. They could easily see the camps of the British troops, though they were so far above them that moving companies looked like marching ants. The tents could not be concealed, and there were besides numerous low sheds, which doubtless sheltered supplies of every description, needed by the army fighting in the trenches further north.

As Frank drew more upon the motors that were keeping up a noisy chorus, the huge seaplane rushed through the air and gave them a change of landscape every little while.

The sun was in plain sight, although just beginning to touch things below with golden fingers. Covering land and water, they could see over a radius that must have been far more than fifty miles.

Billy kept uttering exclamations, intended to express the rapture that filled his breast. In all his experience he had never gazed upon anything to compare with what he now saw spread out below him as though upon a monster checkerboard. African wilds, Western deserts and Polar regions of eternal ice were all dwarfed in interest by this spectacle.

Again and again did he call the attention of his chum to certain features of the wonderful picture that especially appealed to him. Now it was the snakelike movements of what appeared to be a new army heading toward the front, accompanied by a long line of big guns that were drawn by traction engines. Then the irregular line of what he made out to be the opposing trenches riveted his attention. He was thrilled when he actually saw a rush made by an attacking party of Germans, to be met with volleys that must have sadly decimated their ranks, for as Billy gazed with bated breath he saw the remnant of the gallant band reel back and vanish amidst their own trenches.

“Am I awake, Frank, or asleep and dreaming all this?” Billy exclaimed, as he handed the glasses to his chum.

This Frank could readily do because they were running along as smoothly as velvet, and long habit had made him perfectly at home in handling the working parts of the seaplane.

“I wonder what they think of us?” wondered Billy. “You may be sure that every field glass and pair of binoculars they own is leveled at us right now. They must think the French or the British have sprung one on them, to beat out their old Zeppelins at the raiding business! Oh! wouldn’t I give something to be close enough to the commanding general to see the look on his face.”

Frank was looking for something else just then. Although they were flying at such a great height, he fancied that the present security would hardly last. The Germans were only waiting until they had gone on a certain distance; then probably a dozen of their hustling little Taube machines would spring upward and chase after the singular stranger like a swarm of hornets, seeking to cut off escape, and hoping by some lucky shot to bring it down.

The barograph was in plain sight from where Frank sat, and perhaps the quick glance he gave at its readings just then had some connection with this expectation of coming trouble.

Billy interpreted it otherwise. He was afraid Frank, thinking they had gone far enough, was sweeping around to start back toward the British trench line.

“Just a little further, Frank,” pleaded Billy. “There’s a big move on over yonder, seems like, where that army is coming along; and I’d like to see enough to interest our good friend Major Nixon when we get back.”

“I don’t know whether I’ll let you say a single word, Billy,” the air pilot told him, as he relinquished the glasses to the eager one. “That wouldn’t be acting neutral, you know. Besides, there are plenty of the Allies’ machines able to fly, and those airmen like Graham-White ought to be able to pick up news of any big movement.”

They could see patches of snow in places, and much water in others where the low country had been inundated by the Belgians. This was done in hopes of hastening the retreat of the invaders, who despite all had stuck to their trenches and the unfinished canal for months, as though rooted there.

All at once there sounded a loud crash not far below the young air pilots, and a puff of white smoke told where a shrapnel shell had burst.

“Frank, they’re firing at us!” exclaimed Billy, who had made an involuntary ducking movement with his head as the sharp discharge burst upon his ears.

Even as he spoke another, and still a third crash told that the Germans had determined the time was at hand to try their anti-aëroplane guns on the strange seaplane that was soaring above the camps.

CHAPTER VII.
THE “SEA EAGLE” ON PARADE.

“That means we’ll have to climb higher, so that their guns can’t reach!” Frank immediately decided.

It was indeed getting rather warm around them, Billy thought. The shrapnel puffs seemed to be above, below, and on every side, and it was a wonder that neither of them received a wound.

“Only for the speed we’re hitting up, the story might be a whole lot different, according to my notion, Frank. They have a hard job to get our range, you see.”

“Yes, most of it bursts back of us, showing a faulty figuring,” the pilot explained, as he started a corkscrew movement of the seaplane calculated to cause the aircraft to bore upward in spirals.

The guns, far below, kept up a merry chorus. Billy could hear the faint noise made by the continuous discharges, and the puffs of smoke that seemed to rise in a score of places at the same time told him how eagerly the German gunners were trying to strike that elevated mark.

Now the shrapnel ceased to worry Billy, for he saw that none of it seemed to be bursting around them as before. The limits or range of the anti-aircraft guns had apparently been reached.

“We’re safe from the iron rain up at this height, Frank. What does the barometer say?” he asked, with that spirit of curiosity that had made him a good reporter in the old days.

“That’s too bad,” replied Frank, as he bent forward to look.

“Don’t tell me that the only fragment of a shell that’s struck home ruined our fine barometer!” cried Billy.

“Just what happened,” he was told. “At any rate, it’s knocked to flinders; and I think I must have had a pretty close shave. But we can buy a new one when we get back to Dunkirk. As near as I can give a rough guess we must be between three and four thousand feet high.”

“I should say it was a lot more than that,” Billy declared. “But so long as they can’t reach us any longer, why dispute over a few thousand feet?”

He thereupon once more started to make use of the glasses, and had hardly settled them to his eyes than he gave a startled cry.

“Frank, they’re coming up like a swarm of angry bees!” Billy exclaimed.

“Do you mean Taube aëroplanes, Billy?”

“Yes, I can see as many as six right now in different directions, and others are going to follow, if looks count for anything. The word must have been given to attack us.”

“I’m not worrying any,” Frank told him calmly. “In fact, I don’t believe they’ll try to tackle such a strange hybrid aircraft. They can see how differently constructed the Sea Eagle is from all other hydro-aëroplanes, and expect that we must mount at least one quick-firing gun.”

“Then what are they climbing for, Frank? I can hear the buzz of their propellers right now, and let me tell you it sounds like ‘strictly business’ to me!”

“They are meaning to get close enough to let the pilots see what kind of a queer contrivance it is that’s hanging over their camps,” Frank continued in a reassuring manner. “When we choose to turn tail and clear out, there isn’t one in the lot that can tag on after us.”

“I know that, Frank, thanks to those wonderful motors, and the clever construction of Dr. Perkins’ model. But now here’s new trouble looming up ahead.”

“I can see what you mean, Billy. Yes, that is a Zeppelin moving along down there, one of the older type, I should say, without having used the glasses.”

“But surely it will make for us, Frank. A real Zeppelin wouldn’t think of sheering off from any sort of aëroplane.”

“Watch and see what happens,” Billy was told, as Frank changed their course so as to head straight for the great dirigible that was floating in space halfway between their present altitude and the earth that lay thousands of feet below.

The firing had stopped. Probably the German gunners, having realized the utter futility of trying to reach the Sea Eagle while it remained at such a dizzy height, were now watching to see what was about to take place. Many of them may have pinned great faith in the ability of their aircraft to out-maneuver any similar fliers manipulated by the pilots of the Allies. They may even have expected to see a stern chase, with their air fleet in hot pursuit of this remarkable stranger.

If this were really the case, those same observers were doomed to meet with a bitter disappointment.

“Well, what does it look like now?” Frank asked presently, while his companion continued to keep the glasses glued to his eyes as though fairly fascinated by all he saw.

“The Zeppelin has put on full steam, I should say, Frank,” admitted Billy.

“Coming to attack us?” chuckled the other, though the motors were humming at such a lively rate that Billy barely caught the words.

“Gee whillikins, I should say not!” he cried exultantly. “Why, they’re on the run, Frank, and going like hot cakes. I bet you that Zeppelin never made faster time since the day it was launched. They act as though they thought we wanted to get above them so as to bombard the big dirigible with bombs.”

“And that’s just what they do fear,” said Frank positively. “That’s the greatest weakness of those big dirigibles, they offer such a wide surface for being hit. While an ordinary shell might pass straight through, and only tear one of the many compartments, let a bomb be dropped from above, and explode on the gas bag, and the chances are the Zeppelin would go to the scrap-heap.”

“They’re dropping down in a hurry!” declared Billy. “There, I can see a great big shed off yonder, and it must be this that the dirigible is aiming to reach. We could, however, bombard the shed as easily, and destroy it together with its contents. Frank, it makes me think of an ostrich trying to hide its head in a little patch of grass or weeds, and because it can’t see anything, believes itself completely hidden.”

“Well, as we haven’t even a gun along with us the Zeppelin is pretty safe from our attack,” remarked Frank. “We’ve proved one thing by coming out to-day.”

“I guess you mean that we’ve given the Germans something to puzzle their wits over, eh, Frank? They know now that no matter what big yarns have been told about the new Yankee seaplane they tried to steal, it’s all true, every single word of it.”

Billy seemed to be quite merry over it. The fact that the dangerous Zeppelin had fled in such wild haste, shunning an encounter, while the vicious little Taube aëroplanes darted about like angry hornets, yet always kept a respectable distance away from the majestic soaring Sea Eagle was enough to make anyone feel satisfied.

“I admit that at first I was kind of shaky about defying the whole lot, but I’ve changed my mind some, Frank,” he called out a minute later. “Yes, the shoe is on the other foot now. They’re afraid of us! Makes a fellow puff out with pride. There’s only one thing I feel sorry about.”

“What might that be?” asked the other.

“If only Harry could have been along to enjoy this wonderful triumph with us, or Dr. Perkins either. It would have completed our victory. But from here I can see that army on the move as plain as anything. They’re meaning to make one of their terrible drives somewhere along the Yser Canal, perhaps when that air raid comes off that we heard so much quiet talk about.”

“Well, that raid may be held up a while,” Frank told him. “They must believe that French or British pilots are aboard the Sea Eagle right now; and for all they know there are half a dozen just such big aircraft waiting to engage their fleet if it hove in sight of Dunkirk or Calais.”

“Every time we make a sweep around you can see the nearest Taube scuttle off in a big hurry,” ventured Billy. “Why, Frank, some of those machines are carrying a quick-firer with them, but they’ve had orders not to take risks. What would you do if they actually started to close in on us?”

Frank laughed as though that did not worry him very much.

“Why, there are several things we could do, Billy. In the first place we can go higher with the Sea Eagle than any of those flimsy Taubes would dare to venture, though I’d hate to risk it in this bitter cold air.”

“Yes, that’s true, Frank, and like you I hope we will not have to climb any further. It isn’t so bad in the summer, but excuse me from doing it now. We would need two more coats on top of the ones we’ve got, and another hood to keep our ears from being frozen stiff. What’s the other idea?”

“A straight run-away,” explained Frank. “If I really saw that any of them meant business, I could crack on all speed until we were making the entire two thousand revolutions per minute. That would leave them far behind.”

“I should think so,” admitted Billy, who had the greatest possible faith in the ability of the seaplane, as well as the cleverness of its young pilot. “Once we got to going our prettiest and they would look as if they might be standing still. Who’s afraid? Set ’em up in the other alley!”

“I think I’ll show them something to start them guessing,” Frank was saying a minute later. “They haven’t yet seen what she can do under forced pressure.”

“Let her out to the limit then,” pleaded the passenger, who could never experience too much excitement.

So Frank began to turn on full speed, and the wonderful creation of Dr. Perkins’ inventive brain was soon swooping along in a manner calculated to make some of those who were staring through glasses far below gasp with astonishment bordering on awe.

After all, Frank Chester was a boy, and must have felt a natural pride in being able to thus surprise the whole of the Kaiser’s army with his amazing new aircraft. He knew that tens of thousands of eyes must be riveted upon them at that particular moment, from the officers at Headquarters to the mud-spattered and half frozen men concealed in the irregular trenches.

“See the Taubes giving us all the room they can, Frank!” cried Billy.

“Evidently they’re not hankering after an engagement with the Sea Eagle, Billy.”

“They make me think of a flock of wild ducks on a lake when an eagle poises on fluttering wings above them, picking out his dinner,” Billy went on to say. “They scatter and dive and act half crazy; but nearly every time the eagle gets what he’s after.

“Well, all we want is a clear road back over the way we came,” the pilot pursued. “Fact is, we’re not near so dangerous as we look. All we could do just now would be to ram a Zeppelin, and go down with it.”

“But they don’t know that, Frank, which is lucky for us!” declared his chum.

No doubt, Billy, in common with most other boys, must have learned at school the familiar saying that “pride always goes before a fall.” He had just been doing considerable boasting, and his heart was even then swelling with the conviction that he and his chum were virtually snapping their fingers at the whole of the Kaiser’s scattered army with every enlisted man craning his neck in wonder.

Then came the sudden shock, all the more terrifying because so utterly unexpected. It seemed to Billy that his very breath was taken away. The joyous buzz of the motors that had amounted to almost a shriek ceased as if by magic; and the Sea Eagle, shooting forward a bit under the impetus of her great speed, quickly began to volplane toward the earth, thousands of feet below!

CHAPTER VIII.
A SAFE RETURN.

Who could blame Billy if he turned ashy pale at that critical second. He could not believe that this was any scheme of Frank’s for showing off what the great seaplane was capable of, though on previous occasions he had known such a thing to happen.

The one terrible conviction that flashed through his mind was that something had happened to stop their motors at this great altitude; and that the Sea Eagle was now, with ever increasing velocity, heading downward to earth.

If they managed, through any degree of dexterity to escape death, there must always be more or less chance of the machine being wrecked; and even though that catastrophe were avoided, it was sure to fall into the hands of the Germans. Then good-by to their hopes of keeping its construction a secret.

But Frank had been busy meanwhile. He was not the one to be caught napping by any sudden happening. Their present predicament had been accurately discounted by the clever mind that had invented many parts of the strange seaplane.

No sooner did Frank realize that the motive power had ceased than, with a quick snap of the hand, he had turned a valve that was within easy reach.

This allowed pure hydrogen gas from one of the cylinders to rush into the buoyancy devices, which might be called the crowning triumph along the line of insurance against accidents connected with Dr. Perkins’ invention.

As if by magic, the upper wings of the aircraft began to swell until they had all the appearance of puffed-out mattresses. How the eyes of those who were watching down below must have grown round with wonder as they realized that here was something altogether new. It was also a hitherto unheard-of device intended to diminish the terrible risk of a fall ever present with those who go up in aircraft.

The swift volplaning had immediately begun to grow less pronounced, and Billy, feeling that after all they were not going to drop to the ground, drew in his first breath since the accident had come about.

Frank was already busily engaged in examining the stalled motors. So reliable had the same brand always proven in connection with the Sea Eagle type of hydro-aëroplane, that Frank could not remember ever having such an accident occur.

They were now floating aimlessly in space, not having any means of moving save as the wind might chance to cause the seaplane to drift, much after the manner of an old-time balloon.

“Can you make the repairs, Frank, or do we have to hang out the white flag of surrender?” called Billy, in an agony of fear lest their wonderful tryout cruise be fated to come to such an ignoble finish.

“There’s nothing terrible the matter,” came the reassuring reply from the pilot, still working with feverish haste at the motors. “I think I can get things working again in a hurry.”

“Oh! you make me happy by saying that, Frank,” Billy told him. “I was beginning to think I could see the inside of a German dungeon, or a firing squad standing me up against a blank wall. I hope it doesn’t take long, Frank. There, they start their plagued old anti-aircraft guns again!”

Indeed, the first heavy crash of breaking shrapnel not far from the stationary seaplane proved that Billy’s remark bore the stamp of truth. They had rushed down with such impetus that before the buoyancy devices could accomplish the purposes for which they were intended, the seaplane had once more dropped within range of the elevated guns below.

Now having a stationary target to aim at instead of one that was making something like sixty, seventy, or perhaps fully five score miles an hour, the experienced gunners were very apt to send their shells dangerously close, so that at any second, fragments from one, as it burst, might do terrible damage to either the seaplane’s motors or her daring young pilots.

Oh! if Frank could only hurry and repair the motors, Billy was saying over and over again to himself as he clung there and tried to keep count of the numerous sudden puffs of gray or white smoke, indicating the breaking of the shrapnel shells around them.

What if one of them, better aimed than the rest, should shatter those buoyant wings that were their sole means of remaining afloat in the upper air! A rush, an agonized sensation of the earth coming up to meet them, and that would be their last realization of what life meant.

Billy would never forget that frightful agony of that minute as long as he lived. A minute—why, it seemed to the shivering boy as though he must have lived almost a whole year while that furious bombardment kept up; Frank coolly tinkered with the motors.

Then Billy heard his chum calling to him; never had words sounded one-half so sweet.

“Got it fixed. Be out of this in a jiffy!” the other shouted, for there was so much racket around them that words spoken in an ordinary tone could never have been heard.

Then Billy forgot about the crackling shrapnel and the circling Taubes. He had caught the familiar whir of the propellers as the motors started once more upon their work. It was a very soothing sound to Billy’s wrought up nerves.

Immediately the Sea Eagle began to speed forward. Frank’s first act was to set the suction pump to work emptying the great wings of gas, and sending it back to the reservoir intended for storage purposes. This was done because they could never hope to attain any great amount of speed otherwise.

When they were falling, the boys had heard what seemed to be a concerted roar from thousands of lusty throats below. This they knew had indicated the sudden delight of the watching and deeply interested soldiers in the aërial mishap that appeared to have overtaken the wonderful Yankee invention.

These shouts kept up more or less while the anti-aircraft guns were furiously bombarding the nearly stationary seaplane; but as soon as the latter started off again, as though in disdain at their futile efforts, the noise ceased like magic.

Frank first of all mounted higher, until none of the bursting bombs came anywhere near them. Then, feeling perfectly safe from this danger, he set his course toward the southwest.

“Heading home, are you, Frank?” asked Billy, not at all disappointed, for their trial spin certainly had contained enough thrills and dangers to satisfy even such a greedy lover of adventure as the one-time reporter.

“Yes, we’ve done all we set out to attempt, and a good deal more into the bargain,” replied Frank, casting a cautious look to the right and left, not meaning to be taken off his guard by any venturesome German pilot aboard a Taube machine, who might risk all in a last attempt to cripple this amazing seaplane that outclassed anything they possessed.

“You’ve finished pumping the gas back again into the reservoir, haven’t you, Frank? Do you think there was much loss?”

“Not a bit more than two per cent., for we’ve tested that before,” he was informed.

“They’ve given up the pursuit,” Billy observed presently, showing that all this while he had been keeping an eye on those swift flying little Taube machines that had continued to dart hither and thither, like angry hornets, yet not daring to make an attack.

Since there was no longer any visible sign of danger, the boys were able to once more observe the checkerboard picture that lay far below them. Accustomed to being up among the clouds, they knew just how to gauge distances, and in this way could get the relative value of things. A novice would have found his calculations along these lines sadly at variance with the facts.

“For one,” said Billy, his voice showing signs of trembling, “I won’t be sorry to hug up to a stove when we get to our hangar once more. This air is bitter up here, and seems to go right through you. We’re in for a decent spell of weather, it strikes me, Frank.”

“Yes, it ought to last another day or so,” the other replied, as though its condition was of importance.

Indeed, when the wind blew the pilots were kept from making their daily reconnoissance. During storms and snow, or even rain, it was useless to take the risks of venturing aloft, because the view would be so limited, with the earth shrouded in fog or snow squalls, that it would not pay to ascend.

So it was that hundreds of daring aviators would welcome this spell of quiet weather as an opportunity that could not be allowed to slip past without being taken advantage of.

“We’ve passed over the trenches along the canal,” announced Billy, still handling the glasses, and as usual telling the busy pilot what he saw. “Now I can hear the British shouting hoarsely and they seem to be waving all sorts of things up at us. Do you think they know we are supposed to be trying out this seaplane which was really contracted for by the French Government before the war broke out?”

“They have guessed that we must be friendly to their cause, because they saw something of what went on back there when we struck that mine field,” Frank explained without the least hesitation.

He had been dropping lower the while, partly because the air was so keen and cutting so many thousands of feet up and also on account of the fact that they had nothing more to fear from hostile demonstrations.

“There’s the road to Dunkirk and Calais that the Kaiser said his men would tramp along in time to be in town at Christmas,” laughed Billy, pointing his gloved hand downward to where could be seen various detachments of marching troops, with scores of huge motor vans taking supplies out along the fighting line for the men who held the trenches, and the bridge-heads across the river.

“The British, with reinforcements coming up every day, seem to be holding all the ground around here,” Frank was saying. “Can you see Dunkirk yet, Billy?”

“Oh! yes, easily enough. It isn’t such a great distance away from where the fighting is taking place. They’ve heard the roar of the big forty-two centimeter German guns at Dunkirk more than once this winter.”

Still lower they dropped, until at less than a thousand feet they sailed along, now over the water, with the Channel on their right, and the disputed shore of France to the left.

“Will you alight on the water, and then head straight for our hangar, Frank?”

“That is the easiest way to do it,” came the answer, as though Frank had every detail mapped out in his head.

“I warrant you Pudge is standing somewhere, and watching us come along, with his heart beating furiously, ready to fairly hug us after we get ashore.”

Billy grinned as he thus pictured the delight of their fat chum on hearing how magnificently the gallant Sea Eagle had disported in the air high above the German Headquarters, and what a spasm of alarm their coming had sent to the hearts of the various air pilots belonging to the invaders.

With the grace of a monster swan, the seaplane circled around several times and then alighted on the bosom of the water, as softly as floating thistle down. Equally at home in the air or on the water, the strange hybrid craft immediately commenced to move along in the direction of the wooden inclined plane leading by a gradual rise from the water into the elevated hangar.

So ended the amazing and satisfactory trial trip of the Sea Eagle.

CHAPTER IX.
THRILLING NEWS.

“Mumps and mathematics, but I’m glad to see you boys get back safe again!”

Of course that was Pudge, otherwise Ulysses Perkins, expressing his gratitude at the return of the gallant Sea Eagle and the two bold air navigators.

Pudge was close by on the shore when the seaplane ran in to the foot of the wooden trestle, upon which the big seaplane was drawn on the wheeled carriage, built for that purpose, until it was once more safely housed in the hangar.

“Don’t ask a single question, Pudge!” called Billy, “until we’ve got her up the inclined plane, and snugly sheltered from the public view. I guess there must be a thousand people outside trying to see what the Sea Eagle looks like. They must have watched us coming on down the coast, and had a bad case of fright at first, thinking it meant another spell of bomb dropping.”

“Yes, lend us a hand, Pudge,” added Frank, “and help get the machine settled evenly on the little carriage. You know we have it so arranged that she can be hauled up by means of this cable, and by her own motors. I’ll stay aboard to guide things, and you two follow after we’re safely in the hangar, not before.”

Billy knew he meant a rope might possibly break, and it would be dangerous for anyone to be caught upon the trestle by the descending seaplane. Indeed, Billy had a pretty vivid recollection of the narrow escape of the two spies who had barely jumped aside at the time of their downward rush.

Everything went off without the slightest hitch, and the first act of Pudge, after climbing the ascent in company with Billy, was to hastily look over the returned air traveler from the spoon-shaped bow to the opposite extremity.

“Seems to be without a scratch, Frank!” he exclaimed in undeniable glee.

“Why, did you think we had been in some sort of smash-up?” demanded Billy.

“Well, no, not quite so bad as that,” admitted Pudge; “but I knew some of those German spies must have tried pretty hard to capture the craft, and if that failed I reckoned they’d wanted to do something to put her out of commission. Now, please, sit down here and tell me everything.”

“Ours is a long story, Pudge,” said Frank, “as you can judge for yourself when I tell you we’ve been far up over the fighting lines in Belgium, found ourselves bombarded by shrapnel, and threatened by half a dozen Taube flying machines, as well as a Zeppelin!”

“Gosh! all of that?” gasped Pudge.

“Yes,” added Billy, shaking his forefinger at the stout chum, “and before we relate the whole story in detail you’ve got to tell us what happened last night that made you fail to come back when we expected you.”

“Oh! I wanted to, all right,” spluttered Pudge, as though he felt that somehow his bravery or his honor might be involved in the explanation demanded; “but, say, there were three of them, all big husky men, at that, and they caught me unawares just by that turn of the road. It was getting kind of dusk, too, and I never dreamed of trouble till one clapped a hand over my mouth, and the others held me while they tied a bandage around my face. Whee! I was near smothered at first.”

“They were Germans, Pudge?” questioned Billy, interested in the fact that Pudge had also had his share of adventure.

“I heard them talking in German, which made it look that way,” replied the other soberly.

“They didn’t hurt you very much, did they?” asked Billy, looking more closely at their jolly comrade.

“More my feelings than anything else,” replied Pudge, shrugging his fat shoulders disconsolately. “They just kept me there while they waited to catch some sort of signal. I listened, too, and heard some shouting, but that cloth kept me from making out what it meant. Afterward they set me free, and disappeared. I didn’t know what to make of it when I got to the hangar here and found the Sea Eagle gone.”

“You even felt afraid they had grabbed our seaplane, didn’t you?” asked Billy.

“Well, it gave me a bad scare at first,” Pudge admitted, with charming frankness.

“But you got over that later on, eh, Pudge?”

“I did when I heard you calling me from away out somewhere in the dark,” explained the other. “Were you on the water at that time, Frank, because I figured you must be, with that old fog horn sound coming stealing in to me out of that bank of gloom?”

“Yes, that’s where we were, Pudge,” Frank told him. “Now, since you’ve explained all about your own doings, we’ll satisfy your curiosity by telling you the particulars of the trial trip of our sample seaplane. Billy, you can do the talking, if you feel equal to it, while we start a fire here, and warm up with some coffee.”

A fire was soon sending out a fair amount of heat, and the coffee pot placed upon the top of the little sheet-iron stove gave promise of good cheer to come. The aviator boys had enjoyed this social cup many times while working on the assembling of the various parts of the seaplane, so that they had all the necessary accompaniments close by to be used after the coffee had boiled.

Meanwhile Billy had been thrilling Pudge with a recital of all he and Frank had gone through since the fat chum left on his errand. He pictured the dash down the trestle when the determined German secret agents were trying to break in at the doors, so as to seize and run off with the wonderful machine. From that he went on to the adventure in the fog and darkness of the night while they lay on the water of the harbor, and the searching parties came upon them.

Then followed the early morning flight, what amazing things they had seen when passing over the trenches, the fierce bombardment to which they were subjected, the maneuvers of the hostile aircraft, the accident to the motors, and finally their triumphant return to the hangar.

Pudge drew a long breath when the story reached its conclusion.

“And to think that I wasn’t along with you when all those things happened; it’s enough to make anyone weep,” he said, looking so downcast that Frank felt it only right he should try and cheer the poor fellow up.

“Never mind, Pudge,” he told him, “you were doing your duty just as much as any of us. The fact that we made that grand trip over the firing lines doesn’t mean we have any more reason to crow than you do. You can always say that you once had the great luck to be actually taken prisoner by the Germans.”

“Oh! they treated me all right, only that they kept me a prisoner and wouldn’t parole me on my honor not to betray them. Then, that cloth they tied around my face must have been something they picked up, for it seemed like an old rag. But thank goodness it’s all over with now.”

“Yes,” said Billy lightly, “no use ever borrowing trouble about things that are dead and gone. You know they say the mill will never run again with the water that is past. But there’s someone at the door, Frank.”

“I imagine it must be our friend, Major Nixon,” said Frank. “He’s heard that we’ve been away on some sort of trial spin to test things, and has dropped around to learn how we made out.”

“He’s going to be surprised a whole lot when he hears all we’ve got to tell,” said Billy, with a chuckle, as he started over to unfasten the door, upon the panel of which those knocks had been sounded.

It proved that Frank was a good prophet, for the visitor was the red-faced British officer connected with the aviation squad at Dunkirk. His manner betrayed the fact that he had come either to fetch some important news or else to be told something along those lines.

Once again did Billy have to start in. Fortunately, he was a pretty fair story-teller, and enthusiasm with his subject did more or less to help him. The Major was duly thrilled with the graphic account of all the stirring events that had come to Frank and Billy since the afternoon.

Being a man of considerable experience in aviation, though no longer allowed to make an ascent, on account of being subject to dizzy spells, the after effects from a severe accident, Major Nixon at least could enjoy hearing about the exploits of others.

Billy, too, was blunt, and not at all inclined to make himself and chum out to be any sort of heroes. He told the story in a most matter-of-fact way, though reading between the lines the officer was able to picture things about as they happened.

“I’m pleased to hear your grand account of this great seaplane,” he told them when Billy at last told of their safe return to the waiting hangar. “My word, if only we British had fifty like it, I believe we would be in condition to end the war before three months had passed. No Zeppelin would dare enter into the same class. What magnificent craft they would be for protecting the home coast from such bombardments as happened not so very long ago.”

“Well,” said Frank, thinking to strike while the iron was hot, “we’re going to ask that from now on our hangar be guarded against any sort of attack. This seaplane, after certain formalities have been complied with, really will belong to the French Government; so it’s surely up to you to defend the property of your ally from a raid.”

“Your point is well taken, Frank,” the officer told him. “Every hour of the day and night I will see to it that a company of armed guards is stationed around your property, with instructions to defend it against any force of thieves, desperate spies or any other invaders. They will rue the hour they attempt to capture or injure your wonderful seaplane.”

Major Nixon always made it a point to walk around the big air rover, and carefully note its various strong points as developed through the patents of its inventor, Dr. Perkins, U. S. A. He was the only one who had thus far been given the privilege of seeing the odd machine at close quarters; because the boys had the utmost confidence in his honor as a soldier and a gentleman.

It seemed to Billy that the Major spent an unusually long time looking things over on this occasion. Perhaps he wished to verify the statements, to which he had just listened, concerning the stability of the seaplane and its condition for hard service.

When he joined them again, Billy also noticed that there was a most peculiar expression on the other’s red face, of which he could make nothing at the time, although it all came to him afterward.

“Is the seaplane in condition for another trip that might cover several times the distance you did in this trial spin?” he asked.

Billy thought this to be merely a casual question, such as anyone might ask after hearing the story just finished; but Frank, able to see further, believed there might be a meaning behind it.

“All I would have to do would be to replace the liquid fuel that we have used, and after oiling the bearings in a few places, I give you my word, Major Nixon, I would be willing to take the chances of going to Paris and back in the Sea Eagle with as many as two or more companions on the journey.”

Upon hearing that the other smiled as though the answer pleased him. There were numerous attributes connected with Frank Chester calculated to appeal to a man of his observation; and considering the fact that he was an Englishman, usually cold and reserved toward outsiders, the Major had become warmly attached to the boy aviators and their fortunes.

“And now, if you’ll bend your heads toward me, because sometimes the very walls have ears, they say,” he remarked impressively, “I’ll tell you a great secret.”

Realizing that this was no joke, Frank, Billy and even Pudge leaned forward, after which Major Nixon went on to say in a cautious tone hardly more than a whisper:

“It was learned that our friends, the enemy, intended sending out another one of their exasperating raids with half a dozen Taubes. They would drop a few bombs on Dunkirk and Calais and call that a great feat. Now more than thirty seaplanes, guided by some of the most daring of British aviators, plan a gigantic raid on the German sea bases in Belgium to-night, and you can accompany them if you will!”

CHAPTER X.
THE AËROPLANE BOYS IN LUCK.

Thrilled by the nature of the communication made by the British officer, Frank, Billy and Pudge stood there staring at one another.

Of course it was not so very difficult for Frank to understand just why this invitation to accompany the raiding party of British aviators had come to them. Back of it all was the French Government, he felt certain. Before going into the business of making heavy investments connected with the new American seaplane patents it was only natural they should desire to witness an efficient test of the machine’s superiority over any aëroplanes they already possessed.

The contemplated raid would afford such a test. Competent critics, those other experienced birdmen, would be near to gauge the capacity of the Sea Eagle. In other words, the French Government did not want to “buy a pig in the poke.” Unless the hybrid sea and aircraft could meet the requirements laid down, they would not dare risk squandering great amounts of money in those hard times to duplicate her model.

Frank was greatly pleased. It seemed as though he and his chums had received a magnificent compliment in being honored with such an invitation.

“Of course, Major Nixon, you have been authorized to see us, and extend this courtesy?” he asked, as a starter.

“I can show you my credentials in that line, Frank,” the genial officer replied, without the least hesitation or embarrassment, which he accordingly proceeded to do, thus relieving the other’s mind in the beginning.

“Everything is shipshape, sir,” said Frank. “Now let us talk about the conditions under which we are to be allowed to accompany the expedition”

“Please keep your voice lowered as much as you can while I instruct you,” begged Major Nixon.

“You are thinking of those German spies who are said to be everywhere?” ventured Frank, who had heard much talk along these lines ever since arriving at Dunkirk.

Indeed, the stories that passed current concerning spies were astonishing. Most of them Frank did not believe in at all, for he knew they were founded on the fears of the people. At the same time the secret agents of the Kaiser were certainly vigilant as well as bold, and if one had to err at all it were better to be on the safe side.

“In times past I haven’t taken much stock in the wild stories that have been going around,” said the soldier, smiling; “but we certainly know there are spies in Dunkirk at this very hour. In fact, you boys have had pretty strong evidence that your operations while here have been watched day by day.”

“Yes,” remarked Billy, “and after what happened last night we are ready to believe almost anything, sir. I remember reading that sometimes the walls have ears, and I guess it may be so.”

“Under such conditions then it is best that we get our heads close together and talk in very low tones,” said the officer. “There are guards posted all around the stockade now, and yet in spite of that precaution some of those German spies are smart enough to play the game.”

“Anchors and aëroplanes, but this is exciting enough to please even a fellow built like you are, Billy!” muttered Pudge, who was mopping his red forehead with his handkerchief, though the others did not consider it any too warm there in the hangar of the great seaplane.

“I am unable to tell you at this minute the exact hour when the start will be made,” Major Nixon whispered. “Much depends on the state of the weather, and the arrival of the fleet of aëroplanes from across the Channel, for most of them will come from England, you understand.”

“Conditions being favorable, then,” observed Frank, “you believe that by another morning the start of the raiding party will take place?”

“Yes, undoubtedly,” came the answer. “We wish to take advantage of the unusually good weather conditions. Then, besides, we have learned through certain sources of information that the Germans on their own hook are planning an extensive dash with their aëroplanes and dirigibles on the coast cities on the Channel. It is in hopes of balking that, as well as accomplishing other results that more than thirty seaplanes will make this stupendous raid on their submarine bases at Ostend, Zeebrugge and Blankenberghe.”

“Sandwiches and sauerkraut!” Pudge was heard to gasp, as though his breath were almost taken away by the magnitude of this assertion; for he had never as yet seen as many as thirty aëroplanes assembled together, and certainly not in action.

“Is that the only motive of the raid, Major Nixon?” Frank asked, for he invariably made it a point to acquire all the information possible.

“Well,” continued the soldier, “to be perfectly frank with you, there are a number of other objects which such a sudden attack is likely to influence. It is aimed to destroy the railway station at Ostend so as to greatly hinder the movement of troop trains and those carrying ammunition and supplies. Then, at Bruges, other damage may be done.”

“But isn’t there still another big object in it?” insisted Frank.

“I suppose you are referring to the great submarine blockade of the coasts of Great Britain which Germany proposes to inaugurate next week?” said Major Nixon. “Yes, although I have not been so informed, I can guess readily enough that by means of this raid it is hoped to extensively damage their submarine base at Zeebrugge, and injure the movement in the beginning.”

“In other words,” said Frank, “Great Britain means to throw down the gage of battle, and warn Germany she can make just as dashing raids as anyone. No one nation is mistress of the air in this world war—as yet.”

Major Nixon smiled as he heard those last two words, and saw the quick look of pride which the young aviator threw toward the monster seaplane that was housed in that hangar.

“It’s plain that you have the utmost confidence in the ability of your machine to wrest that supremacy from the Germans, if once France secures the right to manufacture a fleet of Sea Eagles,” he remarked, as he laid a hand upon the shoulder of Frank Chester, of whom the bluff soldier had become quite fond in the short time they had known each other.

“Then it is understood, Major, that we keep ourselves in readiness to start out so as to be on the move at dawn, for I don’t imagine such a great fleet of aëroplanes would wish to make a start in the darkness of night.”

“No, there is no necessity of such a thing,” came the quick reply. “In fact, one of the objects of this raid is publicity. We do not aim to creep up and damage the enemy in the dark. We want him to see the astonishing sight of such a mass of darting seaplanes descending on his coast towns like a flock of eagles, and destroying military property, not citizens’ private homes, mind you.”

“I think,” said Frank, “I can speak for my friends here as well as myself, Major, when I promise to be ready for the signal. How will we know when to start out, for we shall all sleep here to-night?”

“There is only one condition which you will be asked to meet,” said the other.

“Then tell us what it is, sir.”

“The French Government will expect to have a representative aboard the Sea Eagle during the flight, not to interfere in the slightest degree with your mastery of the seaplane, but simply to take notes concerning her behavior under every sort of condition.”

“We certainly agree to that condition, Major Nixon,” said Frank heartily. “In fact, I should have asked that one be sent out with us. It is a part of our policy to fully satisfy the authorities we’ve been dealing with for nearly a year, now, that everything we claim, and much more, is possible with our advanced model of a hydro-aëroplane.”

“Very good, and I am pleased to know it,” said the officer. “I shall have to go back to town, now, but I will advise the local representative of the Government that you accept the conditions. By early dawn there will appear here a skillful aviator with written credentials, and I hope his ultimate report will be all you boys hoped it to be. My word! I only wish I were going with you, but other duties must claim my attention.”

He shook each one of them warmly by the hand.

“The best of luck, Frank,” were his last words at parting. “I trust that you may have an experience calculated to dwarf anything that has ever come your way.”

Frank, as he contemplated what a thrilling adventure lay before them, fancied that this wish on the part of Major Nixon was in a fair way of coming true. It certainly would be difficult to imagine a more exciting experience than taking part in an aërial raid, where more than thirty seaplanes started out to bombard strongly fortified coast defenses of the enemy, each raider subjected to a continual fire from every known species of anti-aircraft gun known to modern warfare.

After the soldier had left them, the three Boy Aviators sat around and talked in low tones. They had barred the door, and so far as they could see there was not the slightest chance that any eavesdropper could get close enough to overhear what they said. Nevertheless, the caution of Major Nixon had its effect upon them and there was no loud conversation except when ordinary matters were touched upon.

Frank always liked to “potter” around and give little touches of improvement to some part of the seaplane in which he had such a deep interest. No one knew its good and bad qualities as well as Frank; even its inventor had not studied these points as carefully as the young aviator.

So it happened that from time to time the boy made numerous little improvements that he figured would cause the motors to work more smoothly, or strengthen some part of the framework that showed signs of weakness.

Half a dozen times Frank left his two chums, sitting there killing time, to attend to something connected with the plane. He had carefully examined to find what had caused the accident that gave them such a thrill when thousands of feet above the earth.

“The same thing will never occur again, that I’m as sure of as I am of my own name,” he told Billy, when the other asked him about it.

Several hours had passed since the soldier had left them. Pudge, having taken a stroll outside, came back to report that there were at least a dozen British “Tommies” standing guard around the enclosure in which the hangar had been erected.

“It’s a good thing, too,” said Pudge, “because a crowd has come out from town to hang around here in hopes we’ll make a flight to-day. Oilskins and onions, but I should think there must be a hundred people if there’s one. But those Tommies are ready to use their bayonets on the first fellow who tried to climb up and peep over the stockade.”

“There are two guards, I noticed, down by the end of the trestle, where it strikes the water,” observed Billy, who had been moving around.

Frank was doing some little job under the seaplane, and at this moment came sauntering toward his two mates. Billy, happening to glance up at the other’s face was surprised to see that Frank looked excited; at least his eyes sparkled strangely, and there was a grimness in the way he had set his jaws.

Billy, always inclined to be explosive, might have burst out with a question only that he received a quick and expressive look from Frank, accompanied by the placing of a finger on his lips. Then, as Frank dropped into a chair beside them, Billy leaned over to whisper:

“What’s up now, Frank, that you’re looking so mysterious?”

“I’ve just made a discovery, that’s all,” came the same sort of careful reply. “Fact is, after all our precautions we’ve been outwitted, for there’s a spy hidden in the hangar right now!”

CHAPTER XI.
THE MAN IN THE LOCKER.

“Are you joking, Frank?” asked Billy, though he should have known his comrade better than to believe Frank would try to play any silly trick for the sake of giving them a thrill.

Pudge opened his mouth, but for a wonder even one of his queer favorite expressions failed to drop from his lips. In fact, Pudge was rendered temporarily speechless by the astounding nature of Frank’s communication.

“Not at all, Billy,” said the other, trying to act as though he might be telling them something of small importance. “I watched while I was sheltered under the plane, and twice I saw it shake a little as though some one might be holding the door ajar so as to hear better.”

“Door!” echoed Billy helplessly, as though more puzzled than ever.

“The door of the empty locker we thought we might need for storing things away, but which has never been used,” Frank explained.

“Gee whillikins! now I understand what you mean, Frank,” said Billy. “There is plenty of room in that locker to hold a man curled up.”

“Popguns and pyramids, but how could he ever get there when we’ve been sitting around all morning?” asked Pudge, in a hoarse whisper.

“Only in one way,” Frank told him. “Before they left here last night they must have fixed him there in the locker, believing we’d be back again sooner or later, when some information of value might be picked up.”

“Oh! my stars, Frank,” Billy ejaculated huskily. “What if, after all, he’s heard enough talk here to guess about that big raid?”

Frank looked very serious.

“It’s true that we’ve been pretty careful,” he said, “and most of the time just whispered while we talked about it; but all the same a man with the ears of a spy might have picked up enough to arouse suspicions, and once that’s done the rest would come easy.”

“What can we do about it, Frank?” asked Billy.

“Our good friend, the Major, has extended the invitation to us so that in a way I feel we’re responsible for the secret being kept,” Frank went on to say, as though he might be revolving certain conditions in his mind before deciding.

On hearing him say that Billy began to work the muscles of his right arm, at the same time opening and closing his fingers, as though eager to clutch something.

“I agree with you, Frank,” he hastened to say. “The great secret has been placed in our keeping, and for one I would feel pretty small if it leaked out through any fault of ours. We’ve got to cage that spy as sure as you live.”

“Punkins and partridges, that’s right!” muttered Pudge, who, while not as a rule pugnaciously inclined, could nevertheless assume what he was pleased to call his “fighting face” when occasion arose.

“I’m glad to find both of you are of the same mind,” Frank said. “The only question is to decide what our plan of campaign shall be.”

“P’r’aps some of those Tommies in khaki would be only too glad of a chance to step in and collar the spy?” suggested Pudge.

“But there are three of us here,” objected Billy, “and I don’t see why we should want to call on the soldiers for such a little thing. After we’ve grabbed Mr. Spy and have got him tied up it will be time enough to figure on handing him over to the authorities.”

“That’s what’s worrying me,” admitted Frank.

“About handing him over, do you mean?” Billy demanded.

“Well, you know what the fate of a spy always is,” the other said. “We are supposed to be neutral in this war business. No matter whether our sympathy lies with Belgium, Germany, or France, we’ve got to try and treat them as much alike as we can. Our company has been negotiating with the French Government for a long time, now, over this contract, and so, of course, we have to favor them if anybody; but boys, not one of us would like to feel that we were the cause of a spy being shot or hanged.”

“Oh well, we could kick him off the place after we got him out, Frank,” suggested Pudge so aggressively that Billy chuckled, and started to smooth the fat chum down the back, just as one might a pugnacious rooster who was boiling with a desire to plunge into carnage.

“That sounds all right,” Frank told him; “but you forget the one important thing. He has some knowledge of this raid, and if we let him go it may mean a great disaster to the fleet of seaplanes taking part in the dash up the coast.”

“Whew! looks like we might be what my father would say was between the upper and the nether millstones,” remarked Billy.

“Gatling guns and grasshoppers,” Pudge added, “my father would go further than that, I guess, and say we were between the devil and the deep sea. But Frank, you’re the one to decide that question. What shall we do?”

“There is a way,” Frank announced, “by which we could settle it so the man wouldn’t fall into the hands of the military authorities, who would execute him, and at the same time he could be kept from betraying what he may have learned.”

“Glad to hear it,” said Pudge; “because I don’t want to know I’ve been instrumental in standing a poor fellow up before a file, and getting him filled with cold lead. Tell us about it, please, Frank.”

“After we’ve captured the man we’ll get word to the civil authorities, saying we’ve caught a thief in our hangar, and asking them to keep him safe for two or three days. I’ll go and see the Major myself, and get him to promise that the man will be treated only as a thief and not as a spy.”

“You’ve guessed the answer, Frank,” announced Pudge, with the enthusiasm he always showed when the leader of the aviator boys blazed a trail out of some wilderness in which they had lost themselves.

“Then the sooner we get busy the better,” hinted Billy, again working that good right arm of his as though it might be rapidly getting beyond his restraint.

“We have no firearms, though,” suggested Pudge.

“There’s no need of any,” Frank told him. “I’ll hold this wrench in a way that’ll make it seem like a six-shooter. The rest of you can help pile on the man when we drag him out of the locker, either feet or head first, it doesn’t matter which.”

“Just give me a chance to sit on him, that’s all!” threatened Pudge, at which Billy could be heard to chuckle, as though he pitied anyone who went through that far from enviable experience; perhaps Billy knew from his own associations with Pudge what such an operation meant.

“Now, here’s the way we’ll fix it,” began Frank. “I’ll step over again to the other side of the hangar to work at the motors of the Sea Eagle. Pretty soon you’ll hear me calling to you both to come around and see what a clever little arrangement I’ve fixed up.”

“Which will, in other words, mean the fun is about to begin?” commented Billy.

“When you join me,” continued Frank, “we’ll jabber for a minute, during which I’ll say we might as well go to town and get something decent to eat at noon. That will be apt to put him off his guard. Then we’ll all tiptoe over to the locker, and at a signal throw the door open. As soon as you glimpse him, take hold, and start to pulling like a house afire. That will keep him from trying to fight back or use his weapon, for I guess he’ll have a gun of some kind. Understand it all, boys?”

“Go on, Frank. Please don’t wait any longer than you have to,” pleaded Billy.

So Frank, a minute or two later, called to them to come and see what a splendid little change he had made in the gear of the deflecting rudder of the big seaplane.

It was a thrilling moment for the three boys when they began to move in the direction of the locker where Frank believed a spy had taken refuge many hours previously. As he had suggested, they walked on their tiptoes, each fastening his eager gaze upon the door which they expected to presently pull suddenly open.

When they had taken up their positions according to Frank’s plan, he gave the expected signal.

“Now, everybody!”

The locker door was dragged open in spite of the fact that something seemed to be clinging desperately to it from the inside. No sooner had this been accomplished than the boys, stooping, seized hold of the doubled-up figure they could see in the cavity under the bench, and started to drag with might and main.

“Don’t try to draw a gun or you are a dead man!”—Page [125].

Although the man in hiding made a powerful effort to resist the pressure brought to bear upon him, he was hardly in a position to do much.

They dragged him out, squirming like a rat taken by the tail, and trying to hold on to every object, however small, as a drowning man will catch at a straw. No sooner was he in full view than Pudge dropped down on his back with all his force.

A dismal groan announced that the breath had been pretty well driven from the spy’s lungs; and before he could recover his wits enough to try and produce any weapon Frank clapped the end of his wrench against his temple while he called out in very commanding tones:

“Don’t try to draw a gun or you are a dead man! I’ve got you covered, and will pull the trigger if you so much as move a hand!”

Having in this manner caused the prisoner to behave, Frank hastily searched his pockets and confiscated a stubby little revolver which he found there. Then he told Billy to tie the man’s wrists together, placing them behind his back, with a stout piece of tarred rope that lay within convenient reaching distance.

“Now he’s helpless, and we can let him get to his feet if we want,” said Billy; but Frank thought otherwise.

“It’s better to be on the safe side,” he observed. “So use the balance of the rope around his ankles, Billy. I want to leave you two here while I go to town and make arrangements through Major Nixon to have the man held simply as a thief and not as a spy. I’d like to know he couldn’t get away.”

They found that he was rather a small man, with a cunning face. He did not look very much like a German, and possibly had been picked out for his hazardous pursuit on that very account.

To their surprise he addressed them in the best of English.

“I am an American citizen, you must know, and I have the papers to prove it. My name is Hans Larsen and I came from Sweden many years ago.”

“Oh! is that so?” remarked Frank, who had lately read that many Germans across the sea had been able to secure the naturalization papers belonging to others in order to cross to Sweden or Italy without being taken prisoner by the English naval men, and Frank rightly guessed the spy had fortified himself in that way so as to have some means for escaping death in case of capture.

“Then what were you doing hidden in that locker?” demanded Billy.

“I have no money, and I was hungry,” said the man. “I came here to pick up something I could sell for a few sous, and get some bread. Then I heard voices and afraid to be seen I crawled under there. Let me go and I shall never bother you again.”

Billy laughed in his face.

“They say a lame excuse is better than none,” he remarked, “but when Frank pulled that fierce-looking gun out of your pocket I saw a bright coin fall to the floor. Here it is, and a gold coin in the bargain. An English sovereign at that. I wonder why anyone should go hungry long in Dunkirk these days with all that money in his pocket? Don’t try to trick us, my man. We know why you were hidden in that locker, and you don’t need to be told what a spy can expect when caught in the act.”

The man shut his teeth hard together, and gave a little groan, but said nothing. He evidently expected that the fate he may have dared so often had at last found him out.

CHAPTER XII.
FRANK MAKES A BARGAIN.

“What’s the next thing on the program, Frank?” asked Billy.

“I must go to town and see Major Nixon,” came the prompt reply.

“You mean so as to hand this prisoner over to his charge, don’t you?”

“I want to get in touch with the civil authorities, and make certain arrangements looking to his detention for several days,” explained Frank.

The spy started and looked eagerly at the speaker. His dry lips moved as though he were trying to voice the sudden hope that had flashed through his brain; but no sound followed. Still it could be seen that his despair was not as complete as before.

“But Frank,” interrupted Pudge, “perhaps it won’t be necessary for you to skip out and leave.”

“Tell me what you mean, Pudge?” Frank asked him.

“Use the telephone, and talk with the Major. Yes, it was knocked out of commission by those smarties, but while you were away this morning, having nothing else to do, I amused myself hunting for the break in the wire, which I found and easily spliced.”

“Does it work all right now, Pudge?” questioned Billy, grinning at the thought of the other doing all that climbing, because action of this sort was hardly the forte of their stout chum.

“As good as ever, for I tested it,” he was told.

Frank, however, shook his head in the negative.

“I think I had better go personally and see the Major,” he told them.

“How’s that, Frank?” remarked Billy quickly. “Do you suspect that in some way those men may have tapped our wire?”

“Well, I wouldn’t put it past them,” came the reply. “Spies have to be up to all sorts of clever dodges, and that would be just in line with their work.”

Billy gave a whistle to indicate the state of his mixed feelings.

“Gee whillikins, to think that we haven’t whispered a single sentence along that wire but what some outsider was drinking it in! Frank, I guess you’re right, and that in a particular case like this it’s best to deal at first hand with Major Nixon.”

“I’m sure of that, boys,” the leader told them in his quiet, convincing way.

“And I suppose that you want us to stick by the hangar while you’re away; is that the game, Frank?” Pudge wanted to know.

“Yes, and be mighty careful how you take your eyes off the prisoner for even a minute,” Frank directed. “I’m going to look all around the place before I leave, so as to make sure there isn’t another spy hidden away in some corner. As soon as I step out, fasten the door and keep it so. I may call you up over the wire, and if I do you’ll know my voice. Besides, to make absolutely sure I’ll give you our old signal. That’s about all.”

He bustled around for several minutes, and thoroughly explored the whole interior of the hangar. When Frank had finished his task he was absolutely sure that no intruder larger than a mouse could have escaped his search.

Once outside he made for the gate, where he found a couple of rosy-cheeked British khaki-clad Tommies on guard, with whom he exchanged pleasant greetings.

“Don’t let a single soul get past here until I come back again,” he told them. “I’m going to see Major Nixon, who is a personal friend of mine, and my business with him is very important. We’ve caught a—well, a thief in the hangar, and I want him to take charge of the rascal. If you hear any row in there while I’m gone have some of your men go up to the door; but keep the gate guarded meanwhile.”

The two soldiers promised that they would attend strictly to business. They knew something of what these young American boys were doing over in France, and that their presence had to do with the closing of certain arrangements with the French Government that had been under way before the breaking out of the war.

Frank walked off.

He was feeling very well satisfied with the way things were coming out. It was true there might be some cause for uneasiness in connection with the determined efforts of the spies to either steal or ruin the machine; but Frank believed he and his chums, assisted by the Allies, could keep it from being destroyed through a bomb placed under the hangar by a secret agent of the Kaiser.

One could not go very far in the neighborhood of Dunkirk in those stirring days without being visibly reminded that it was a time of war. Soldiers in detachments were moving this way or that; tents could be seen in the fields; artillery was passing along the heavy roads bound for the front, where the British army in the low country along the Yser Canal must be getting ready for that long-heralded drive that was to usher in the new policy of aggression in the early Spring.

Everywhere he looked Frank could see signs of this feverish life. How different things were across the ocean in his own beloved land; and how thankful he was that peace lay upon the great country of which he was a son.

He knew where he was likely to find Major Nixon, for he had been to see him at his quarters before now. As he walked quickly along with a springy step, Frank was laying out his plan of campaign. It was like him to prepare for possibilities, because he was determined that, as far as he could prevent it, he and his chums would not take sides in this terrible struggle for supremacy, any more than could be prevented.

Coming to the building in which the British had their Headquarters he was stopped by a sentry who demanded his business.

“I must see Major Nixon on very important business,” Frank told him. “I hope he is in his quarters, for I wish to send my card with a line on it to him.”

Of course all that the sentry could do was to summon a noncommissioned officer, to whom Frank repeated his request. It happened that the sergeant had seen Frank walking arm in arm with the Major, and hence knew that they were friends.

“He is very busy just now, and gave word that he was not to be disturbed except on most important business,” the sergeant informed him.

“This is a matter,” the boy told him impressively, “that concerns grave issues connected with the plans of your leaders, and I hope you will see that the Major gets my card.”

“I will carry it to him myself,” announced the sergeant, which he accordingly did, and soon came back nodding his head.

The few urgent words written on the card had the desired effect, for the sergeant immediately asked Frank to follow him.

“Major Nixon told me to say that he would see you, sir,” was the message he gave the boy.

Presently Frank entered the soldier’s room. He found the Major impatiently awaiting his coming, and with an extended hand in the bargain.

“My word! but you’ve given me a beastly shock by what you write,” he was saying as he shook hands. “‘Plans threatened with disaster—must see you at once!’ Now be good enough to tell me what it all means, for I’m shivering with dread. If anything happened to upset all those splendidly arranged plans for the raid, we’d be broken-hearted, you know.”

“Before I say a single word, Major Nixon, I want you to give me your promise to agree to a certain stipulation I shall make. It simply concerns a man’s life; and will not interfere the least bit with your ideas of military rules.”

“That’s a singular request to make, Frank, but I think I know you well enough to feel sure you will not bind me to anything that would touch upon my honor. I promise you then that you shall have your way; for I imagine you want to have the disposal of this unknown man in your own hands.”

“That is just what I want, Major,” returned the other quickly. “And now listen while I tell you of a remarkable thing that happened after you left us this morning.”

“At your hangar, do you mean?” asked the soldier, looking startled.

“Yes.”

“I hope you don’t intend to tell me any of our men have proven false to their trust and betrayed you, Frank; because I happen to know that the aviator corps expects great things of that invention of Dr. Perkins’, should it eventually become the property of the French Government.”

“There has been no traitor in the camp, Major,” the other hastened to assure him. “But nevertheless we have learned that all the while you were there talking to us, and while we have been discussing the intended raid in low tones among ourselves, there was a spy concealed in the hangar who must have heard more or less of what was said, despite our precautions.”

The soldier jumped to his feet. He looked almost frightened as he stared into the face of Frank Chester.

“You are sure of what you say, are you, Frank?” he asked with an effort.

“Oh! there isn’t the slightest doubt about it,” came the reply.

Then Major Nixon began to breathe easier. He saw that Frank was smiling, and his common sense told him the boy would not be likely to show such freedom from anxiety if things were as bad as he had at first feared.

“Frank, tell me the rest without delay. I know you’ve got good news back of this astonishing disclosure. Where is that spy now?”

“In the hangar still,” replied Frank.

“Did you take him prisoner?” demanded the Major eagerly.

“Yes, and I’ll tell you how it was done, sir. We had quite a little circus for a short time, believe me.”

Major Nixon listened, and as he heard how Pudge sat down upon the surprised eavesdropper whom they had dragged from the locker, he even smiled, for that terrible fear had by now left his soul.

“My word! what great luck that you caught him before he could send any sort of signal to his companions!” he exclaimed. “And we must see to it that he does not have a chance to even wink an eye toward anyone. It would have ruined everything if he had slipped away. I am a thousand times obliged to you, Frank, for being so much on the alert. It would have ruined my own career if the break had been traced back and placed on my shoulders. We will see to it that this spy gets all that is coming to him.”

“Oh! but you forget your promise, Major Nixon!” remarked the boy coolly.

The soldier looked at him and frowned.

“But Frank, a spy is a dangerous sort of reptile, no matter on which side he is working,” he objected. “These Germans have the most complete system of secret espionage ever known. It is hard to keep anything from their knowledge. This man knew the risk when he hid there in your hangar. He should pay the penalty of his venture. He can expect nothing less than death.”

“Wait, Major Nixon; please remember that he is my prisoner, not yours. If I had spoken the word he could have been set free. You gave me your solemn promise that I should have the say of his fate if I handed him over to the authorities.”

The soldier pondered these words for a minute before continuing.

“Tell me just what you’ve got in your mind, my boy,” he said, “and I feel certain that I can agree to it, because I know how sensible you are.”

“Then listen, sir,” said Frank impressively. “We three are Americans, and while we may sympathize with the Allies in this struggle at the same time we do not hate the German people, but feel the warmest friendship for them. We would not care to remember that we had turned over this spy to the military authorities to be shot. It would grieve us more than I can tell you, sir.”

“But you have a plan, Frank, of course?” ventured the other.

“Yes.”

“Which, it is to be hoped, will protect our great secret?”

“Here is what I want you to agree to, sir,” Frank told him. “We will turn this man over to the civil authorities of Dunkirk to be considered solely in the light of a sneak thief who meant to steal something from our hangar and dispose of it so as to buy food. He has papers to show that he is by birth a Swede, but an American citizen by adoption.”

“Ah! yes, but those have undoubtedly been stolen, and are being used for a purpose anyone can understand,” declared the soldier.

“Yes, that is what we believed, sir,” said Frank. “At the same time if he were shot it might raise an unpleasant tension between my Government and the Allies. As I look at it, the main thing you want to do is to so arrange it that this spy can in no manner communicate with any of his fellows. Am I right there, Major?”

“Yes, yes; that is the principal thing we must consider now, Frank.”

“All right, that can be done just as well if he is shut up as a thief, and at the end of three days, after the raid is a thing of the past, allowed to take his departure from Dunkirk with a warning that if caught again he will pay the penalty with his life.”

Again the soldier pondered. He did not like to let the spy off so easily, for like most bluff fighting men, Major Nixon felt an aversion for those clever secret agents who could block the plans of generals through securing information in advance.

Finally he gave a sigh and smiled at Frank.

“My word! but you know how to handle matters, Frank,” he observed. “Of course I can see just how you and your fine chums must feel about this thing; and on the whole I do not blame you. Yes, I give you my promise again that it will be done as you say. We will take the man to a place of security where he cannot find a chance to communicate with his kind in any possible way. He will be known simply as a suspected thief on the records. And after the raid is over with, I myself will see that he is led to the outskirts of the town, and let go with a warning. Is that sufficient, Frank?”

“Yes, sir, for I know your word is as good as your bond,” Frank told him. “I feel I have done my duty without being instrumental in sacrificing a life.”

CHAPTER XIII.
NOT CAUGHT NAPPING.

Frank was perfectly satisfied with the promise given him by Major Nixon. He knew the bluff British soldier would keep his word to the letter. While the man who had been caught hiding in the hangar of the young American aviators would be taken to a place of security and kept carefully guarded, in order to prevent his knowledge concerning the contemplated aërial raid from leaking out, at the same time his life would not pay the penalty of his capture.

After some more conversation covering the matter Frank, knowing the other to be very busy, took his leave.

“A last word of warning, my boy,” said the soldier, after shaking hands. “Keep on the alert wherever you go in Dunkirk. While the place itself is loyal, and is thronged now with soldiers of every type, at the same time we know there are many secret sympathizers with the other side here trying to learn the plans of our generals, so that they can communicate them to the Kaiser’s leaders.”

“But why should I be picked out for trouble?” asked Frank.

“Because they know that you are here to complete a deal entered into with the French Government in connection with your wonderful seaplane before this war was dreamed of. They would be willing to do something to prevent you from standing between their plans and the securing or destroying of the machine in the hangar.”

“I had not thought of it in that light,” said Frank, disturbed more or less.

“Pardon me for saying it,” continued the Major, “but they understand that if you could only be made to disappear your companions would be much easier to hoodwink, and their plans looking toward destroying the Sea Eagle would be crowned with success. You will be doubly careful, Frank, I hope.”

The boy promised this. Even though he might not be willing to admit that these secret agents of the Kaiser would dream of attempting any violence, at the same time he saw the soldier was really concerned about him.

So they parted with mutual good wishes.

Frank found himself again on the streets of the French seacoast city. Dunkirk was a far different place in these strenuous war times from the other days, when peace lay upon the land, and men went about their customary vocations of fishing, trading, and disposing of the products of the rich soil.

Now everywhere he looked Frank could see soldiers, and then more soldiers. They thronged the principal streets, and passed in and out of the shops buying things that appealed to their fancy. There were all manner of strange foreign troops to be met with—Gurkhas from far-away India; Canadians who resembled the Rough Riders of our own Spanish War times; Colonials from Australia or New Zealand; and many others who interested the boy very much.

Then, with the warning of Major Nixon still ringing in his ears, Frank suddenly became aware of the fact that he himself was an object of interest, though there was nothing about his make-up calculated to attract attention in all that strange collection of men from the four quarters of the globe.

Several times, on glancing hastily about him, he had noticed a certain man dressed like a citizen apparently staring into the window of a store. Frank began to believe the man was following him, and so he made a test to prove it.

“I like that, now,” he said to himself, with a chuckle when again he found that he had not shaken the unknown off his track by slipping into a certain side street, for the man was standing there on the curb as he turned, and calmly brushing his sleeve as though utterly unconcerned.

“I wonder if they would dare try to stop me on the way to the hangar,” Frank was asking himself, though he immediately added: “that’s hardly likely, for there’s really no time when I’m out of sight of soldiers on the road, because they’re going and coming constantly. I could even fall in behind a regiment if I wanted, and have plenty of company all the way to the gates of our compound.”

Just then he found himself attracted by the actions of a couple ahead of him, a man of middle age and a woman. Apparently she had been seized with some sort of vertigo, for the man was acting as though dreadfully alarmed. He had thrown an arm about her, and was looking around in an appealing way.

It happened that Frank was about the only person nearby, and it was only natural for him to hasten forward.

“Oh! please help me support my wife, young sir!” exclaimed the citizen as Frank arrived. “She is fainting, and just when we had reached our home here. Would you mind supporting her on the other side, and assisting me to get her to the door?”

An appeal like that could not be easily resisted, especially by one so ready to help others as Frank Chester had always been in the past.

Somehow it did not appear to strike him as singular that the citizen should be so fluent in his English when he was supposed to be a Frenchman. All Frank thought of then was that the man was in difficulties, and it would be next to nothing for him to lend the other a helping hand.

So he took hold on the other side of the woman who was acting as though swooning. Frank could not but notice that she appeared anything but fragile.

The door of the modest looking house was close by, and between them he and the distracted husband managed to half lead, half drag, the fainting woman up to it. The man immediately opened the door with one hand.

“Please assist me a little further, and I will be so thankful!” he pleaded.

Frank might have actually entered the house, only for a little thing that he had noticed. As they approached the door he had seen the man cast a quick glance upward toward the second story. The latticed blinds were shut, but as Frank used his eyes to advantage he believed he saw someone’s face back of the screen.

Like a flash it struck him that the man must have made some sort of quick signal to the party who was hidden up there. Frank became cautious in that second, remembering the warning given him by Major Nixon.

These spies were up to all manner of trickery in order to carry out their well-laid plans, and might not this pretended swooning of the woman be only a bait intended to coax him into a trap?

Frank immediately released his hold of the woman, and he noticed that she did not appear to be in danger of falling after he had withdrawn his support, which in itself was a suspicious sign.

“Oh! I hope you will help me just a little further!” exclaimed the man. “Inside is a chair, and if we could place her in that it is all I could ask of you. Thank you a thousand times for what you have done already; but do not leave me just yet.”

It seemed hard to refuse, but Frank steeled his heart. He was positive by now he had been made a victim to a deep-laid plot, and if he but stepped within that open door something unpleasant was sure to happen to him.

“You will have to excuse me, but I can go no further,” he said hastily.

The man said something half under his breath. Frank saw that the woman was apparently suddenly regaining her senses, for she had thrown out a hand, and seemed to be trying to clutch hold of his sleeve.

The boy had no difficulty in avoiding the contact, however, thanks to his suspicions. He dodged back, and then with a smile turned and walked quickly away. When he glanced over his shoulder a minute later the couple had vanished, evidently going into the house, which Frank could imagine must be a nest of spies.

“That was a pretty close call for me,” he was saying to himself as he walked on; “and I can imagine there’ll be a hurried exodus from that building inside of a few minutes if I cared to hang around and watch. They’ll be afraid that I may tell on them, and have the soldiers surround the place. But it isn’t my business as a neutral to have German spies arrested and shot.”

Frank sauntered on. He had a few errands to attend to, some small supplies to purchase connected with the seaplane, for new wants were constantly cropping up in that line.

The little adventure caused his blood to warm up, but Frank had been through so much in his past that he had by this time come to take such things as a matter of course, and accept them philosophically.

“If that was intended for a stall,” he said to himself presently, “it shows how desperate they’re getting about our disposing of the Sea Eagle to the French Government. Why, you’d think orders had gone out in Berlin to prevent the transfer by hook or by crook. Certain it is these people are risking their lives in the effort. But they will have to get up pretty early in the morning to best us, that’s all I can say, even if it does sound like boasting.”

Though remaining watchful, he was soon busy with his errands. No one brushed elbows with him in the stores but that Frank used his eyes to take note. Those who could arrange such an ingenious scheme as that swooning lady and the call upon him for assistance might be equal to other games of like character.

He managed to accomplish his several duties without any further cause for alarm, and was once more on the streets observing all that happened. A constantly increasing push of eager observers toward a certain point told Frank there must be something of an unusual interest taking place there, and consumed by the same curiosity he joined the throng, for he had heard someone say the ambulances with the wounded had just come in from the front.

CHAPTER XIV.
THE PERIL IN THE SKY.

Day after day the wounded from the front were being received in Dunkirk, Calais and other places along the coast. They were usually taken further on as soon as their immediate wants could be attended to.

In many cases the stricken soldiers would be carried by train to the large Red Cross hospitals in and around Paris. Then besides this, on many a night a steamer would start from Dunkirk across the Channel bearing hundreds of British back to their own shores, where they could receive the best of care among their people. These voyages were made when possible in the gloom of night, and at full speed, in order to avoid the risk of having the vessel torpedoed by lurking German submarines, ready to deliver crushing blows to her enemy’s ships.

Frank stood in the crowd and watched the transfer of the poor fellows to the temporary hospital. They were mostly British soldiers who had received their injuries while trying to hold the trenches against some fierce drive on the part of Bavarians or Prussians.

As he saw one after another swathed figure borne on stretchers from the ambulance motors into the hospital, Frank felt a sense of pity for all these who were suffering on account of this terrible war, no matter on which side they chanced to be.

He finally turned away, not caring to see any more such pitiful sights. He marveled at the brave front displayed by even the most dreadfully wounded men, who tried to greet the crowd and smiled through the mud that plastered their faces.

Remembering what he and Billy had discovered in connection with the gathering of a new army back of the German trenches, Frank expected that in a few days there was bound to be a greater stream of wounded pouring into Dunkirk than ever before, because a desperate attack was doubtless contemplated.

When he learned from Major Nixon that some of the Allies’ aviators had brought in the news concerning that gathering host of gray-clad soldiers, Frank realized that he could speak of it without reservation, since it would not be giving information as to the enemy’s contemplated plans.

Remembering one more errand which needed his attention, Frank, after leaving the vicinity of the Red Cross hospital, had immediately started to look after it. He was through with it and actually starting for the hangar when once again he became aware of the fact that a sudden confusion had broken out. People were shouting in an excited manner, as though a mad dog had broken loose and was coming down the main street of Dunkirk.

There was no difficulty in learning what was the matter. That wild cry of alarm was becoming very familiar to the ears of the worried citizens of Dunkirk these stormy days.

“The Germans are coming! The Germans are coming!”

In French and in English this shout was being carried along, constantly added to by scores of voices. People rushed pell-mell this way and that, many dodging down into cellars, as though seeking safety from some terror that was likely to descend on the coast city like a cyclone.

Those who were not yet running had their necks craned, and their eyes turned upward toward the northeast. Frank stepped over to where he could see better, and then he also “rubbered,” as Billy would have called it.

On numerous occasions the German aviators had conducted an organized raid on Dunkirk, dropping dozens of terrible bombs in what seemed like an indiscriminate fashion. Possibly these were in the main intended to damage the camps or accumulated stores of the British legions; but if so the aim of the men in the Taubes was singularly bad, for the majority of the bombs had thus far either exploded in the open streets, or shattered private houses.

Many innocent persons, including women and children, had suffered from these explosives, and it was not singular then that whenever the cry was raised that the “Germans were coming,” meaning a raiding flock of aëroplanes, there would ensue a mad panic in the streets of the French city.

“There are several moving things over there away up in the heavens,” Frank told himself as he gazed in more or less excitement. “Even without a glass I’m almost ready to say they can’t be Taubes.”

He stood there watching and waiting until the soaring objects drew closer, when their true identity could be discovered.

Frank, being an aviator himself, quickly detected certain things that the common observer might never have discovered; and which told him the half dozen specks in the sky that February morning were birds and not aëroplanes.

“Some gulls flying high,” he murmured as he watched. “Yes, there they circle around, which aviators bent on bombarding the city and then running off in a hurry would never think of doing.”

He told those near him that there was nothing to fear, as the suspected Taubes were only harmless birds. The cheering word was passed along from mouth to mouth, and some of those who only a few minutes before were looking very peaked and white commenced to laugh, trying to make out that they knew all along the advancing specks were only birds.

By degrees even the shivering inmates of the cellars learned that it was a false alarm, and ventured to appear again.

“And I suppose this happens several times every day,” Frank mused as he watched the arteries of traffic once more begin to flow naturally. “While little damage that amounts to anything has been done by the bombs, the coming of the Germans is looked forward to with dread. I suppose if a flier happened to be brought down with a well directed shot from a gun it would give the people more pleasure than anything they could wish for.”

It struck him that possibly the other boys might have heard something of all this excitement and would be worried about him. So Frank stepped into a store he knew of and proceeded to get the hangar on the wire. There was some little difficulty at first, as though a good many people were trying to communicate with their homes for some purpose or other. Finally a voice called in good English:

“Hello! that you, Frank?”

“Yes, that’s who it is, Billy. I only called you up thinking you might have heard all the shouting, and wonder what it was.”

“Oh! some of the guards here guessed it, and we’ve been watching the gulls through our field glass. But how about the other business, Frank; is it all fixed?”

“I’m coming back right away,” Frank told him. “Soon after I join you, there will be something doing. I’ll tell you the rest when I get there; but everything is going on O. K. So-long, Billy. Keep watching, for they’re ready to try everything under the sun to gain their end. I’ve got a new story for you when I come.”

Frank by this action had not only accomplished his purpose of relieving the minds of his chums, but at the same time he had made sure that things were unchanged at the hangar.

Determined not to take any risks that could be avoided, Frank waited until he saw a battery of field-pieces moving along the road that led close by the gate of the hangar. Perhaps the guns had come over from England on the previous night, and being badly needed at the front, were starting forth.

This was the opportunity he wanted. By keeping alongside the guns and caissons he could defy any hidden danger. If there were spies waiting to waylay him in some rather lonely spot, just as they had Pudge on the preceding night, the presence of those young khaki-clad warriors seated on the gun carriages and ammunition carts would foil them.

There was no trouble. Possibly Frank might not have been held up even though he chose to take the walk without any protection; but when in doubt it was always his policy to “play safe.”

When he again found himself in the hangar, the others were eager to hear what he had promised to tell them.

“You’ve been having another scrape of some sort, like as not,” ventured Billy, pretending to look morose, as though he begrudged his comrade that privilege while he and Pudge were only sitting there killing time.

Frank thereupon related how he had been drawn into rendering assistance when the said-to-be wife of an apparent citizen of Dunkirk, who spoke excellent English without a French accent, appeared to faint close to the door of her own home.

The other boys were thrilled by what seemed like a narrow escape on the part of their comrade.

“Ganders and gridirons, Frank!” exploded Pudge after listening with distended eyes to the account given by the returned chum. “That was a narrow squeak for you, as sure as anything.”

“Yes,” added Billy, “they had it all laid out to trap you. If you’d dared to step inside that open door I reckon you’d have been tapped over the head, and when you came to again it would be to find yourself in some old damp and moldy cellar. I give you credit for tumbling to their smart game, Frank.”

“Bayous and bullfrogs, they certainly do want to get hold of this bully machine of ours the worst kind, and that’s a fact!” spluttered Pudge.

“But tell us about the Major, and what he agreed to do?” asked Billy.

“It’s all fixed just as we figured it,” replied Frank. “I want this man here to understand what has been done, so come over to where you’ve got him.”

The prisoner had been watching them eagerly. He must have guessed that Frank had been gone to settle about his fate, and, if ever a man looked nervous, he did, as the three boys advanced toward him.

“Listen to something I want you to hear,” said Frank. “We know what you are, and that if you were given in charge as a spy you’d likely be shot by to-morrow morning. But we are American boys, and not at all inclined to have the blood of a German honestly serving his Fatherland on our hands. Do you understand what I am saying?”

“Yes, go on,” muttered the man, brightening up, though still anxious.

“I have arranged it with the authorities that you will only be looked on as a petty thief. You will be held in close confinement for a few days until it is certain that any information you may have picked up while here in this building will be useless. Then they will take you out of the city and set you free, with a warning never to be seen here again if you value your life.”

Now the man’s face lighted up in a smile.

“That is much better,” he said, after drawing a long breath of relief. “We thought you were on the side of the Allies, because you meant to turn it over to the French Government.”

“You must remember,” said Frank impressively, “that this machine had been over here, boxed but not assembled, for months before the war opened. My company had a contract with the French people, who insisted on representatives being sent across to demonstrate the new flier; otherwise they threatened to seize it, and make duplicates without our receiving any remuneration—the necessities of war. That is why we have come, and are even now trying to carry out the terms of that agreement. You can tell your people that only for this our company would not dream of making aëroplanes for one side or the other. They could not be shipped out of the United States, anyway.”

“I understand your position,” said the man; “and while it explains many things it does not change our design to prevent the enemy from profiting by your improved type of machine. If by any means it can be stolen or destroyed we believe we are only doing our duty by the Fatherland in risking our lives to attempt it.”

“Well, here comes the patrol to take you to the city prison; and, remember, you are to insist that you entered our hangar to steal, not to spy on us,” Frank told him.

CHAPTER XV.
ON GUARD.

“You will restore to me my papers, I hope?” remarked the man.

“If you mean the naturalization papers that stamp you as one Hans Larsen, formerly of Sweden,” replied Frank, “I am going to put them in your inside pocket. But they will be taken by the officials, and I doubt if you ever see them again. They must know they are either stolen, bought, or forged, and that you only carry them to give trouble in case you are arrested.”

He was as good as his word, for he had taken the papers to show the Major in case any proof were desired after his story had been told.

Then came the file of British soldiers, direct from Major Nixon. They brought a note from the officer to Frank and his chums, desiring that the prisoner be turned over, and also stating that the word he had given Frank would be religiously kept.

The spy walked away in the midst of his guards, who had orders not to let him communicate with anyone on the way. In order to make more positive of this, they had a covered wagon close by, in which he was to be conveyed to the jail.

“I’m glad we’re free from him,” said Billy, after they had watched the party leaving the stockade.

“You don’t think there would be any attempt made at trying to rescue him while they’re on the way?”

“Sugar and sandwiches, but I should hope not!” exclaimed Pudge.

Frank did not seem to be worrying about such a remote possibility.

“No, I don’t think they’re numerous enough to risk an encounter with a dozen armed Tommies looking for trouble, just as Pudge here would look for his breakfast,” he observed.

“Now we’ve got the place all to ourselves,” said Billy. “There’s such a thing as being overcrowded, as the backwoodsman remarked when he heard that another family had started a clearing three miles away from his shack. But I’d like to have been down in Dunkirk when they sighted those gulls coming sailing along, ever so high up in the air.”

“Dories and dingbats, but I warrant you there was some excitement to the square inch,” Pudge insinuated.

Frank laughed as he stretched himself out on a bench to rest.

“You missed a grand sight,” he told them.

“Lots of people scared, I take it?”

“Well, they were fairly crazy,” he was told. “If a menagerie of wild animals had broken loose and come to town it could hardly have created more of a panic than when that cry sounded through the streets: ‘The Germans are coming!’ Men, women and children all ran this way and that. Some dodged down into cellars, while others crawled under front door-stoops, as though that would save them in case a bomb burst close by. It was a panic, all right, and I never saw anything like it in all my experience.”

“They must have felt silly after they found out what it really was?” Billy went on to say.

“Oh, not so very much,” he was told by the one who had been on the spot, and was in a position to relate things at first hand. “You see a good many started to make out they knew the dots must be birds, and said they had just been carrying on in that excited way for a lark.”

“To be sure,” declared Billy, “that’s the way lots of people always try to crawl through a little hole when caught with the goods on. Some of the others, I reckon, laughed it off, and admitted that they didn’t care to be blown up; that they got plenty of that sort of thing at home, as it was. But, Frank, how about our own program?”

“You mean about staying here and being ready to start off when we get the word—is that it, Billy?”

“Yes; shall we stick it out here the rest of the day?”

“I think,” said Frank, “none of us have any need to leave the place again until we start the motors and open up on the second trial spin, this time with some of the best British aviators along to observe how the Sea Eagle carries herself.”

“Do you think there will be a representative of the French Government aboard to take notes along the way?” asked Billy.

“That’s my understanding of the case,” he was told.

“Well, it ought to settle the matter of our business, Frank.”

“Just what it must,” came the reply. “We’ll give an exhibition of all the Sea Eagle is capable of doing in a way to make those other seaplanes look sick. Then we’ll expect to have the deal closed. That’s my understanding of the bargain.”

“But, Frank, whatever are we going to do for eats between now and to-morrow, when we come back from the raid up the coast?” asked Pudge, with a despairing expression on his fat face that would make anyone believe he had lost his last friend; or else just heard the news that he was to be hanged in three hours.

“I’ve fixed all that,” the other told him, “and right now I think I see the wagon coming with a lot of good stuff, such as can still be had in Dunkirk if you’ve got the francs to buy it with.”

Pudge was comforted by hearing such glorious news. He immediately took up his position outside the door from where he could keep an eye on the road close to the stockade gates.

“What are you doing out there, Pudge?” called Billy.

“Sandwiches and sauerkraut, but you wouldn’t want to run the risk of having that grocery wagon miss the place and drive past, would you, Billy?” demanded the sentinel; and the others let him alone, knowing full well that Pudge would not allow any accident of that sort to come about as long as his voice held good.

It turned out that Frank had bought a whole assortment of things to eat; indeed, Billy declared he believed they could stand a siege of a whole week with that lot of foodstuffs to fall back on.

“Three days, anyhow,” assented Pudge, who evidently had a different viewpoint from Billy when it came to sizing up the lasting qualities of edibles.

With the aid of the little stove they prepared a lunch, and really enjoyed it immensely. Pudge seemed to be reminiscent, for he brought up numerous half forgotten times of the past when in company with Harry Chester they had enjoyed many a similar repast, cooked under strange conditions it might be, but never to be wholly forgotten by those who took part in the feast.

Then the afternoon came and it was a long one to the three chums shut up for the most part in the hangar. The fire was kept up in the stove, because there was a tang to the February air so close to the Channel.

Frank went carefully over every part of the seaplane to make certain it was in the best shape possible for the long journey they had before them under conditions that no one could possibly foresee. He did not mean to neglect the slightest thing that could add to their comfort and safety.

Pudge had managed to make himself a pretty cozy nest with a couple of blankets, and he put in part of the afternoon “making up for lost sleep,” he told them. It was a standard joke with them that the fat chum was always far behind in his customary allotment of sleep; somehow or other he never did seem able to fully catch up.

Billy and Frank often stepped outside and took an observation. This not only included the weather but the conditions existing on the harbor, where there were boats of various descriptions to be seen, for the most part unloading war material sent from Great Britain in spite of Germany’s submarine warfare.

“This has been a pretty good day for aërial work, Frank,” suggested Billy. “What about the prospects for to-morrow?”

“I think we can count on it holding about as it is for another twenty-four hours,” came the answer, “and then a change is about due. It’s still cold enough to snow, and I expect we’ll meet a lot of snow squalls when we’re making that trip up the Belgian coast.”

“Do you really believe there’ll be that many seaplanes in the bunch—thirty or more, the Major told us?”

“They have planned to make this raid a record breaker, it looks like,” said Frank, “and will try to get out every machine they have a pilot for. It’s going to be a feather in our caps to be able to say we accompanied them, no matter what amount of damage they manage to inflict on the submarine bases, or railway stations and gas or oil tanks of the German army.”

“Well, I think we’re in great luck to get the chance to go along, Frank; though, of course, we don’t mean to throw a single bomb, or do the least thing to harm the Kaiser’s army. As I look at it the main purpose of our being allowed to accompany the squad of raiders is to let them see what cards we’re holding in this invention of Dr. Perkins. The French Government officials want to be shown, just as if they were from Missouri.”

“They’ll see a few things calculated to make them open their eyes, unless I miss my guess,” said Frank, with quiet confidence; for he knew what the Sea Eagle type of hydro-aëroplane was capable of doing when properly handled, and only longed for the opportunity of showing those British aviators, some of them well-known air pilots, the crowning triumph of Yankee ingenuity.

“It’s getting on toward evening now, with the sun near setting time,” remarked Billy, as though he felt that a load was taken from his shoulders with the passing of that almost interminable day.

“There’s a steamship coming in,” Frank said. “It’s taking all sorts of chances of being torpedoed, even if the Germans have said they are holding back until the eighteenth to start the reign of terror.”

“Do you really think the submarine blockade is going to work?” asked Billy.

“Honestly I don’t see how it can,” Frank replied. “They have only a certain number of the latest undersea vessels capable of staying away from a base for a week. These can’t be everywhere, and are liable to be sunk by torpedo boats. I’ve no doubt the Germans will punch holes in a good many small steamers; but as a rule the big ones can run away from them. I guess it’s a whole lot of a bluff, between you and me.”

“Will Great Britain dare them to do their worst, do you think, Frank?”

“Yes, even knowing that they threaten to sink merchant vessels and their crews of noncombatants without giving warning. Somehow or other it does seem to me that Germany is doing everything possible to make outsiders distrust her. But I suppose we can’t look at things the same way they must from inside, especially since England threatens to starve Germany into submission.”

“There’s the sun going to set,” remarked Billy.

They stood and watched it go down, and the gray of evening begin to creep across the cold sea. So that night in February closed in. Like a grim phantom the steamer came stealing into the harbor, with few lights showing.

“Let’s go in where it’s warm and comfortable,” said Billy. “Frank, since we have plenty of stuff along with us why not make an allowance of coffee for the men who are standing guard over our plant here. A mug of hot coffee would take the chill out of their bones, I’m thinking.”

“A good idea, Billy, and thank you for suggesting it. We’ll find what Pudge says, and carry it out. With the lantern we can make the rounds, and see that no sentry is omitted.”

With such sentiments spurring them on, the boys entered the hangar and found that Pudge was already deep in the pleasing duty of getting supper ready. Hardly had they mentioned the subject of treating the guards to a cup of hot coffee than he announced that he was heartily in accord with the scheme.

CHAPTER XVI.
THE COMING OF THE DAWN.

“Just in time to help me out in planning a bill of fare for supper, too,” Pudge told them. “There are some tinned meats here, but I’d prefer something good and warm.”

That difficulty was soon swept aside, for the others nominated several dishes they chanced to be exceedingly fond of, and Pudge found he was going to have his hands full preparing them with such limited accommodations.

However, willing hands make light work, and both Frank and Billy were ready to give him all the assistance required; so that in the end they had quite a feast spread upon the little drop-table that took up no space at all when not required for use.

It was a peculiar supper-setting, with only that one lantern to give them light. Of course they could have used the acetylene lamps, but their supply of carbide was rather low, and there could be no certainty about obtaining a further amount, so Frank thought it best to husband what they had.

The weird appearance of the big seaplane added more or less to the strangeness of their surroundings. Still, by this time, all of the boys had become so accustomed to seeing its bat-like wings, and the boat body with the spoon-shaped bow that they would have missed it had the hangar been empty.

Over the meal they chatted in low tones, discussing many things connected with their mission across the sea. Little was said concerning the contemplated dash laid out for the following morning, because in the first place they knew none of the particulars; and then again the raid was the Allies’ secret, not theirs.

The unexpected presence of that concealed spy had given them a rude jolt. They appeared to be living in an atmosphere of espionage; and somehow it seemed as though hostile eyes and ears might be close by, even though unseen.

When finally they were through, it was remembered that they had decided to give the chilled guards a treat; so Pudge brewed a copious amount of strong coffee that was of a rich dark color, and had the “odor of ambrosia,” as Billy called it.

“Since you’ve done so much, Pudge,” remarked Frank, “you’re going to be the one to go along with me on the rounds. So get that big tin cup, and we’ll carry the can of condensed Swiss milk with us. We might as well give them the coffee just as they fancy it, either black or with the fixings.”

Pudge beamed on his chum. Evidently he had not expected to be favored with an invitation like this; for as a rule he was apt to be left behind on account of his well-known clumsiness.

Frank, however, was wise enough to carry the steaming pot of coffee himself, as an insurance against spilling. If Pudge did happen to trip over some unseen obstruction and measure his length he could hardly do worse than spill the thick condensed milk, or dent the big tin cup.

So they started forth, and coming to the gate first of all surprised the two khaki-clad Tommies there. How eagerly they in turn quaffed the contents of that common tin cup can be imagined, for the night air was growing cold, and a dismal prospect stared them in the face.

Frank carried the lantern in one hand; it was in the dark of the moon, and he meant that none of the guards should make a mistake and fire upon them for unwelcome prowlers.

News of their coming was sent on ahead, each sentinel calling out to the next one; and in this way the boys made the complete rounds, neglecting none.

When they finally returned to the building it was with an empty pot, and the satisfaction of knowing they had done something to cheer up the brave fellows who were protecting their property.

Frank himself went the rounds of the hangar once more to make sure that everything was as it should be. There was a sense of responsibility resting on him that the others did not feel in the same degree, for Billy was one of those care-free individuals, and as for Pudge, did you ever know of a fat, good-natured boy worrying?

“I hope we don’t have any trouble between now and dawn,” Billy was heard to say as they began to get things ready for sleeping, each having a blanket, as well as some cushions with which to form a rude bed.

“Yes, because to-morrow ought to be a big day for the Sea Eagle Company, Limited,” added Pudge, swelling a little with pride as he pronounced that name. “In fact, it promises to eclipse anything we’ve ever stacked up against before in all our travels.”

“It was all very fine,” commented Billy, “to knock around the Moon Mountains in Africa, meeting up with wild beasts and wilder men; it was thrilling to be away down there in the frozen regions of the Antarctic; but let me tell you all those happenings rolled into one couldn’t equal a trip over the fighting lines of two great armies in a death grapple along the trenches.”

“I’m not going to get one wink of sleep this whole night, thinking about it,” asserted Pudge, shaking his head in a sad fashion; but somehow his threat did not seem to give either of his chums the slightest degree of anxiety, for they knew what an enormous propensity Pudge had for sleep.

It may have been about ten o’clock when they all lay down and tried to lose themselves in slumber. The lantern had been extinguished, but Frank had things fixed so that if any sudden necessity arose he could press a button that was close by his hand and illuminate the interior of the hangar with the searchlight connected with the seaplane.

Just as they expected, Pudge was breathing stertorously before seven minutes had crept by, proving his dismal foreboding to have been an empty threat. Billy was the next one to drop off; and finally Frank, too, lost track of things after he had tried various expedients in the hope of forgetting himself.

They were aroused by a sudden loud noise that sounded like an explosion. All of them sat upright as though brought in contact with a galvanic battery; but Frank desisted even when his hand was in the act of reaching for the button connected with the light.

If that had been a bursting bomb dropped by some hovering German Taube, for him to betray the exact position of the hangar by starting up the brilliant electric searchlight would be the height of folly.

“What could that have been, Frank?” Pudge was asking in trembling tones; for as it afterward turned out he had been having a weird dream, and his first thought on being so rudely aroused was that the top of a volcano he was exploring had been blown off by an eruption, sending him a mile high.

“The Germans have made a night raid, and are trying to smash the Sea Eagle, after seeing what she could do to their machines and dirigibles!” declared Billy, as if his mind had already been made up.

“Do you think so too, Frank; and are we apt to be blown up any second now by a better aimed bomb than that first one?” Pudge demanded, evidently trying hard to control himself, and show that he could face danger with an undaunted front.

Frank had had time to think. He realized that several things conflicted with such an explanation of the mysterious explosion. Voices, too, outside could be heard, and it was evident that the guards were calling to one another.

“On second thought,” Frank ventured to say, “I don’t believe that could have been a bomb. It didn’t make near enough noise, though perhaps we thought it pretty loud on being waked up so suddenly.”

“Then what could it have been, Frank?” demanded Billy.

“I’ve got an idea one of the guards may have fired at some prowler,” replied the other; “in a minute or so I’ll take the lantern and go out to see.”

He insisted on going alone, and the other two remained back of the barred door awaiting his report. Frank was gone about twenty minutes when his signal was heard on the other side of the door. Upon being admitted he at once eased their fears.

“After all, it was the discharge of a gun, just as we guessed,” he observed. “One of the guards believed he saw a shadowy figure creeping along. He challenged, and on hearing the bushes shake as the unknown started away, the sentry shot.”

“Perhaps, after all, it was a false alarm?” suggested Billy.

“No, it was a prowler, all right,” said Frank, “for the sergeant and myself went out to where he told us he had aimed, and we found not only footprints in the dirt, but specks of blood as well, showing that the soldier had winged the spy.”

“Tamales and terrapins, but that is thrilling news, Frank!” exclaimed Pudge. “Did you try to follow the trail, and see if the poor fellow was lying around anywhere?”

“It made for the road, and we lost it there,” said Frank. “I reckon it was not a very severe wound, for while the man evidently limped he did not lose much blood. Not wanting to be away from the hangar any longer than we could help, the sergeant and myself came back.”

“One good thing,” remarked Billy, “those chaps will have learned that we are on the job, all right. They’ll be careful how they come sneaking around here again, or try to blow up our plant. What time is it now?”

“Just two o’clock,” announced Pudge, referring to his nickel watch by the light of the lantern which had not as yet been extinguished.

“Between four and five hours more to put in before day comes ‘a-peeping over the hills,’” half sang Billy, as he started to arrange his rude bed again, for in the haste of their turning out, things had been thrown aside rather recklessly.

There was no further alarm that night. Apparently, those who would have given much to have wrecked the hangar with its contents, so as to prevent its being taken over by the French military authorities, feared to again approach the guarded stockade.

Billy, after all, was the first to discover signs of dawn through the window which was secured with the heavy wire mesh. He immediately aroused the others and they proceeded to get the coffee on the stove.

Just when they would receive the signal was uncertain; so that it was considered the part of wisdom to be prepared in advance.

“I wonder where we’ll take the next meal,” Pudge remarked, as they sat there at the table and satisfied their appetites with what had been prepared.

Billy was about to make some sort of grim joke on the possibility of their not ever needing another “feed,” but on second thought he desisted. It was not a subject to be made fun of, he concluded, because the danger of an accident was always in evidence when far up among the clouds.

“We’ll make up a snack to take along with us,” said wise Frank. “It may come in handy, you know.”

“Pumpkins and partridges, but it does take you to think up things, Frank!” cried Pudge, beaming on his comrade, for that proposal was right in his line of weakness.

“There’s someone at the door, Frank!” announced Billy.

The day was coming on, as Frank could see when he partly opened the door. He discovered a stranger standing there, a swarthy looking, slender man, who was apparently a Frenchman, if appearances went for anything.

“Pardon, but have I the pleasure of addressing M’sieu Frank Chester?” he asked.

“That is my name,” replied the boy. “Have you come from Major Nixon?”

“I have a letter here from that gentleman,” said the other. “It is to prove that my identity is correct. For I am to accompany you on this interesting trip, to discover what strong points your seaplane develops. My name, young M’sieu, is Armand Le Grande.”

Frank was thrilled when he heard the name, for he knew that Major Nixon had been wise enough to send one of the most famous of all French aviators to accompany the Sea Eagle on its dangerous mission.

CHAPTER XVII.
NEWS BY WIRELESS.

Frank immediately opened wide the door and bade the other welcome. He even held out his hand, and made the French aviator feel that they were delighted to know he was to be with them.

“First of all be pleased to read what Major Nixon has written here,” said M. Le Grande, after being introduced to the other boys, who were surveying him with natural curiosity, because they, too, recognized his well-known name.

Frank quickly read the contents of the note. It was to the point, for the British officer was a man of comparatively few words.

“My Dear Frank:

With this I introduce my friend Monsieur Armand Le Grande. You know what he has done in your line. He will be your passenger on the trial trip. Remember, you are the sole commander, as M. Le Grande is there simply to take notes, and advise, if you care to ask his valued opinion at any time. The best of luck to you all, and may this day be one never to be forgotten, both here and in the tight little island across the Channel. When we receive word by wireless, I shall let you know over the phone.

Yours sincerely,

John Nixon, Major.”

Since Frank knew the handwriting well he could not have any doubt concerning the authenticity of the letter. It happened that he had also seen pictures of the noted French birdman, and they corresponded with the features of the man who had come to them.

If Frank, therefore, had in the beginning entertained the slightest suspicion, it was by now wholly allayed. Sitting there while the newcomer enjoyed a cup of black coffee, they talked in low tones of the contemplated voyage.

It was wonderful to see how calmly they discussed the tremendous possibilities of the great raid by aëroplanes on the enemy’s works. Ten years back, had anyone ventured to affirm that in so short a time scouts would be sailing through the upper currents at the rate of two miles a minute, and even “looping the loop” in a desire to prove their mastery over air, he would have been set down as visionary and a dreamer.

Frank went to the double doors opening on the trestle that ran down to the water and took an observation.

“There is some haze on the sea,” he announced, “but it is rising, and I think we are going to have a fair day for the trip.”

They had made all preparations, so that when the summons came there should be no occasion for unnecessary delay. Knowing that they would find it bitterly cold far up among the clouds while moving at high speed, all of them were careful to don the warmest clothing possible. As they wandered about the interior of the hangar they resembled mummies to some degree; but appearances count for little with the venturesome men who risk their lives while emulating the birds.

All at once there was a quick angry buzz.

“The ’phone, Frank!” cried Billy.

Frank darted over and clapped the French receiver to his ear.

“Hello!” he called.

“Who is it?” asked a voice he recognized as belonging to the Major.

“Frank Chester; is that you, Major Nixon?”

“Yes, has he arrived, Frank?”

“If you mean M’sieu Le Grande, yes. He’s here with us, waiting for the time to come when we make the start.”

“Well, it is here. I have called you up to tell you, Frank.”

“Have you received a message by wireless from across the Channel, sir?”

“We have,” replied the Major. “It told us that the fleet had started from Dover cliffs, and would be across in less than half an hour, if all went well.”

“Good news! You make us happy when you say that. Shall we get out at once and be ready to join them when they show up?”

“Lose no time, for they may be here sooner than expected; and again the best of luck go with you, Frank, my boy. May you and your chums return in safety, and your passenger bring back a glowing report. That’s all; now get busy!”

Frank swung around. His young face fairly glowed with animation and expectation.

“How about it, Frank?” asked Billy, as nervous as ever.

“They’re on the wing and heading this way. Everybody get aboard while I fling open the doors and fix it to start!”

There was no confusion because they all knew exactly what was expected of them, and everyone had his place arranged.

Frank swung aboard as the big seaplane began to move. In another second they had passed beyond the doors and commenced to descend the trestle leading to the surface of the bay.

The seaplane took the water with the grace of a swan. There was something of a splash when the connection was made, but that odd bow so like a spoon had been built especially to spurn the water, and so the craft skimmed along just as a flat stone hurled by a boy’s hand will skip over the surface until its momentum has been exhausted.

“There’s something of a crowd over there watching us, Frank!” announced Billy, as he pointed to the shore, at some little distance away.

“Could they have known about what we expected to do,” remarked Pudge, “or is it just the idle crowd that was chased away yesterday by the guard, come to see what’s on the program for to-day?”

“The chances are some of those spies are among the lot,” Billy said at a hazard.

“If they are they’ll be kicking themselves soon because they can’t get word to their friends up the coast,” Pudge continued, looking as though he considered that he might be going to have the time of his life, as no doubt he was.

Frank did not start up. There was no necessity for doing it, since he had no desire to show off before the Dunkirk people, and it was the part of wisdom to conserve all his resources for the strain that awaited them.

He had his field glasses in his hand, and with these he now began to scan the heavens toward the west, veering a little to the northwest. The others waited anxiously to hear what he might discover.

“Nothing in sight from here,” announced Frank; “but then that was to be expected. We are low down on the water, and there are more or less streaks of haze in the air to interfere with a good view.”

“It’s too soon to look for them, anyway,” added Pudge.

“How long do they expect to be on the journey across the Channel, Frank?” Billy inquired.

“From what Major Nixon said, I should guess from twenty minutes to half an hour,” Frank explained. “It all depends on what air currents they strike, and whether they meet with any accidents on the way.”

“There’s our friend the sergeant waving to us from the shore,” announced Billy. “He doesn’t know what’s going on, but he wants you to understand he wishes you all kinds of good luck.”

“Oh!” suddenly cried Pudge, “what’s that over there, Frank! Focus your glass on it and tell me! I hope it isn’t one of those sassy little Taube machines come to bother us just when we want to be let alone.”

“No fear,” he was told by Frank as soon as he caught the far distant object that had caused this outbreak on the part of the fat boy. “That’s only a gull circling around in the sunlight.”

“Hadn’t we better be up so we can join the fleet without wasting any time?” asked Billy

“No need,” Frank assured him. “I understand that they mean to swing in here, and then make a fresh start straight away up the shore.”

“But why should they come in here at all, when they could just as well have headed straight from Dover to Antwerp and Zeebrugge?” demanded Billy, who with that reporter instinct of his always wanted to know the why and wherefore of everything.

“There are several reasons, I believe,” Frank went on to say. “For thirty seaplanes to cross the Channel with its variable winds is a big feat, and it was to make sure all was well with each member of the fleet that they laid out to start fresh from here. Then, I fancy, several other machines are waiting here to join them, so as to make the raid as big as possible, and strike a note of alarm along the naval bases of the coast.”

“Now I understand better,” admitted the other, always willing to listen to any explanation given by Frank, for whose opinion he entertained considerable respect.

The minutes dragged. Even Pudge manifested unusual impatience, and kept craning his fat neck in the endeavor to scan the sky toward the west, as though in hopes of making a pleasing discovery ahead of Frank with his glasses.

“There goes one man up in his biplane!” remarked Billy, who had happened to turn his head and glance back toward the city, attracted possibly by a distant humming sound that was strangely familiar.

“And a second following him in a monoplane,” added Pudge. “I suppose now those fellows will join the squad that’s meaning to do some damage to interior points like Bruges.”

Both the boys looked toward Frank appealingly, as though they hoped he would think best to follow suit, but he did not make the slightest move. Instead, he held the field glasses again to his eyes as he swept the heavens far to the west for signs of the coming squadron of navy aëroplanes and seaplanes that had left the cliffs of England, sailing high to avoid the fog that lay upon the Channel there.

“It must surely be twenty minutes from the time they started by now,” urged Billy presently.

“Just that to a fraction,” announced Pudge, looking to see.

“They may have met with contrary winds up there and be delayed,” urged Frank. “Because it seems so quiet down here is no sign that the conditions are the same a mile high. Be patient! I expect to soon have some good news for you.”

“I surely hope nothing has happened to break up the tea party, once it’s got off on the trip,” grumbled Billy.

Pudge said nothing more, but sat there watching Frank. He knew they would learn of the coming in sight of the fleet first of all from the one who carried the magnifiers; and hence he kept his eyes on the face of his chum.

When Frank lowered the glasses Pudge gave a soft wheeze, as though he had been fairly holding his breath meanwhile; then as soon as the other started to look again Pudge resumed his former occupation of watching for signs.

Even the longest night must have its end, and this absorbed vigil on the part of the fat boy was not without receiving its reward.

When Frank, on the next occasion, not only hastily lowered the glasses but passed them along to Billy, Pudge knew the crisis had arrived at last.

“There they come!” cried Billy, as soon as he had clapped the smaller end of the field glasses to his eyes. “Oh! what a raft of them I can see! Must be a hundred in that bunch, Frank, anyway, all of fifty if there’s one!”

But Frank knew how Billy was prone to exaggerate, without meaning to deceive.

“Let M. Le Grande take a look, Billy,” he suggested, which aroused the other to a remembrance of the fact that they had as their guest a most famous aviator who should be treated with every consideration.

Pudge did not ask to look. He was too busy watching Frank, who had made as if to turn on the power and start things going. For, after skimming over the surface of the water, the big seaplane would mount up like a bird on the wing.

CHAPTER XVIII.
OFF WITH THE AIR RAIDERS.

“Zip! we’re off!” cried Billy, as he heard the familiar whir of the motors, and felt the forward push of the sea and air craft.

Pudge was not so accustomed to being aboard one of the Sea Eagles when starting out on a cruise. His father, knowing the customary clumsiness of Pudge, had preferred as a rule that the fat boy stay upon the solid ground while his more agile chums attempted the aërial stunts.

But Pudge complained so much that Frank had thought it best to let him accompany them on this wonderful journey. It was likely to eclipse anything they had ever experienced before, and must ever remain as a memory worth while.

The speed increasing, they were soon rushing over the surface of the harbor at a furious rate. Then, as Frank slanted the ascending rudder, they left the water to course upward at a low angle, which, however, could be increased as they circled the harbor.

Loud cheers came to their ears from the shore, where that crowd had been standing. They were echoed, too, from several other points, showing that all Dunkirk must be on the alert this morning, as though it might be in the air that wonderful things were about to transpire.

“Are those cheers for us, do you think, Frank, or because they’ve discovered the fleet coming along?” Billy asked, although he had already waved his hand toward the shore.

“It’s hard to tell,” Frank replied. “Though they must have glimpsed the bunch heading this way, and guessed what it all means. I don’t see any person running to hide in a cellar, as they do when the Taubes are around.”

Mounting higher, they waited for the arrival of the fleet. It was a sight never before witnessed. The air was fairly filled with buzzing seaplanes of various patterns, jockeying for position much as is seen on the race course before the signal to start is given by the firing of a pistol.

“Listen to all the racket, will you?” cried Pudge, and indeed the noise of so many motors and whirling propellers did sound strangely.

“It’s like a young Niagara, that’s what I’d call it!” declared Billy. “Why, sometimes you can’t hear yourself think for the Bedlam that’s broken loose. Say, tell me what the Germans up the coast will think has struck them when this flock descends on Zeebrugge, and batters away at the docks and the submarine bases.”

“They’re all under the charge of a central seaplane, too,” added Frank. “For, if you notice, the signals are always sent from that one just passing us now.”

One of the muffled figures in the other aircraft waved a hand at them. Something was said at the same time, which Frank took for granted must be a question as to whether they expected to accompany the raiders.

He nodded his head in the affirmative, at the same time displaying a little red, white and blue flag he carried, and which must have considerably astonished the pilot of the British seaplane, evidently the chief controller.

“I did that so he might know we didn’t expect to drop any bombs, or have a part in the raid itself,” Frank explained, turning to his companions.

“They’re all worked up over seeing such a whopping big seaplane here,” remarked Pudge, with a touch of the old pride in his voice. “They’re having the surprise of their lives right now, let me tell you. I’m glad they know that it’s a Yankee machine.”

“But, Frank, as we understand it, all these bomb-droppers don’t intend to go to one place, do they?” asked Billy, as he watched the whirring machines flit past like so many big dragon flies.

“No,” came the ready answer. “When up the coast a piece, there’ll be a division starting inland to damage the railway station and try to get at the supplies the Germans have gathered at Bruges, as well as some other points.”

“Well, what about us then?” asked Billy.

“Yes,” added Pudge, also deeply interested; “do we go on with the seaplanes and keep tabs of what they do up around Ostend and Zeebrugge, or else switch off and go over the land the same as you and Billy did yesterday?”

“I’ve fixed all that with M. Le Grande here,” Frank told them. “He expressed the wish that we might see fit to keep with the main body along the shore, because it is expected the most spectacular feats will be attempted there.”

“Gee! I was hoping you’d say that, Frank!” Billy exploded.

“Suits me to a dot, too!” Pudge followed by saying.

“I hope they are going to start right away,” added Billy.

“There’s a message being sent up by heliograph,” explained Frank. “Of course, we can’t read the flashes, but it’s meant for the man in the leading plane. I expect it will tell him everything is all right for the start.”

He proved a true prophet, for immediately afterward some signal was given that caused the entire assemblage of aëroplanes to cease their evolutions and head in a long double string up the coast.

The boys, despite the clattering of propellers and the humming of many striving motors, could catch the distant wild cheers that the assembled people of Dunkirk sent after them. It was a benison of good wishes, and a hope that the object of the great raid might be fully accomplished.

Frank kept somewhat above most of the aircraft. He had several objects in doing this, chief of which was the design to show that he was in a class by himself, and not to be included in those who had come forth to fight. Besides, it allowed them to observe all that was going on below; as well as being in a position to show the pilots of the fleet a few little things connected with the strange looking Sea Eagle that would cause them to feel more or less astonishment, and envy as well.

“Will you show them something, Frank, now that we have the chance?” asked Pudge.

“It will have to be before we get to the first place they expect to bombard, then,” Frank replied, meaning, of course, that once the work of the fleet began there would be no time for any of them to manifest any interest in the evolutions of the American built aircraft.

When Frank had moved a lever that called for all speed, and the motors were working at the astonishing rate of almost two thousand revolutions a minute, it seemed as though they had left the rest of the fleet far in the lurch. Green flames spouted from the exhausts, for Frank had opened the muffler in order to get every ounce of speed out of the motors.

They could see the pilots of the other seaplanes looking up at them in mingled wonder and admiration, for, like the jockeys of race horses, it is the ambition of every aviator to possess the fastest going machine on the market.

Having secured a free section of space to himself, Frank proceeded to put the wonderful Sea Eagle through her paces. He showed what could be done in various ways, and while possibly most of those other craft were capable of accomplishing similar tricks, the fact was made patent that the superior size of the American made hydro-aëroplane did not act as a bar to the ability of the Sea Eagle to maneuver in a dexterous fashion while going at that tremendous rate of speed.

“Now we’ll have to stop, and mount a little higher,” Frank remarked, having circled around and found himself once more back of the leaders in the procession.

“There go several aëroplanes off to the right!” announced Billy. “I reckon that’s the detachment told off to tackle Bruges and other interior places.”

“We’re coming to Ostend!” Frank told them, pointing down to where the city of the celebrated bathing beach could be seen, with the houses and hotels close to the famous sandy stretch of shore.

There were boats in the harbor, and they must be German owned or they could not have come there. Billy, using the glasses, could see that the most tremendous excitement had seized upon every one in sight. People were rushing in every direction, soldiers as well as civilians; the rays of the sun glinted on cannon that were being hastily changed, so as to point upward.

“There goes the first anti-aircraft gun!” called Billy, as a faint boom reached their ears from far below.

“Watch what the fleet pilots do!” Frank told them.

Apparently the plan had been well worked out, and every pilot knew exactly what was expected of him. Maps of the region had been carefully studied in order that the position of each vulnerable point of attack might be known.

If there was a railway depot which the Germans used every hour of the day, and the loss of which would cripple their transportation facilities, that was picked out to be an object of attack. Here was a mole alongside of which possibly submarines tied up, and its destruction would deprive the enemy of a valuable station. Further on a large shed marked the spot where great stores had been gathered, and if a bomb could only be exploded in the midst, it was going to mean that there would later be a shortage of provisions. An oil tank, an ammunition magazine, a forty-two centimeter gun, such as battered the forts at Liège to pieces, all such were fair objects of attack wherever they could be found. The one order that had been given to every pilot was to avoid destroying the property of civilians as far as possible.

As Frank and his chums looked down from their higher level they saw a sight such as had never before been witnessed by human eyes. The air was filled with a flock of circling, dodging aëroplanes, with puffs of white smoke breaking above, below, and in some cases amidst them, as the guns on the ground were fired again and again in hopes of bringing one or more of the venturesome craft down.

Various explosions far beneath proclaimed that the bombardment from the sky was in full blast. Most of their ammunition, however, would doubtless be kept for the more important base at Zeebrugge, where raiding submarines were wont to start forth on their daring excursions through the waters of the Channel, seeking to destroy British and French merchant vessels or ships of war.

Already the leading seaplanes had passed over the watering place known as Ostend and which before the war had been a famous summer resort. Doubtless their departure would be watched with mingled feelings by the thousands of German soldiers who had been interested observers of this wonderful sight in the heavens. They would also doubtless wonder what was going to happen when the aërial fleet returned, as it surely must, to its base at Dunkirk.

“How about Antwerp?” asked Billy. “Think they’ll take a turn up there, and drop a few reminders on the railway station, or some of the forts they say the Germans have been building up again?”

“I hardly think so,” Frank replied. “This is a raid on sea coast places, as I understand it. They want to strike at the submarine bases so as to upset the plans of the Germans for next week, when the blockade of the coasts of Great Britain and Northern France goes into effect. They’ll do some damage at Bruges and Blankenberghe I expect, just as we shied a few at Ostend; but the main thing will happen when we get to Zeebrugge.”

“I think that must be the place just ahead of us right now, Frank!” called out Billy, who was again using the glasses, bent on seeing everything that occurred; for he realized that they were highly favored by fortune in being given a chance to witness such strange sights.

“Yes, that is Zeebrugge,” Frank admitted. “Now we’ll see something worth while, if no snow squall comes along to shut out our view!”

“Pirates and parachutes,” cried Pudge, “but I hope that doesn’t happen to us.”