Straight out toward the side of the tarmac it moved jerked downward diagonally, until it rested only a few feet above the ground.

Then suddenly Dick felt the plane quiver, as if released from the power of the force that had held it. It nosed down and crashed, rolled over amid the wreckage of a shattered wing. The concussion shot Dick from the cockpit clear of the smashed machine.

He landed upon his head, and went out instantly.

CHAPTER IX

The Invisible Emperor

It was the sound of his name, spoken repeatedly, that brought Dick back to consciousness. He opened his eyes, blinking in broad daylight. He stared about him, and the first thing he saw was Luke Evans, regarding him anxiously from a little distance away. He saw that it was Luke who had spoken.

He had heard the old man distinctly. The condition of inaudibility was gone.

Not that of invisibility. Dick stared about him in bewilderment. For a moment, before he quite realized what had happened to him, he thought he had lost his mind. Underneath him was a thick rug, beneath his head a pillow; he could feel both of them, and yet all he could see was the open country, a clearing with shrubbery on either side, and, beyond that, a luxurious growth of tropical trees. Under him, to all visual appearance, was the bare ground.

He moved, and heard the clank of chains. He looked down at himself. His wrists were loosely linked to a chain that seemed to stretch tight into vacancy and end in nothing. His ankles were bound likewise.

And both chains appeared to be of solid silver, but thick enough to give them the strength of iron!

Then he perceived that old Evans was bound in the same way.

"Rennell! Rennell!" repeated the old man in a sort of whimper. "Thank God you've come out of it! I was afraid you were dead."

"What's happened?" asked Dick. "Where are we? Didn't they get us?"

"They've got us, damn them!" snarled old Evans. "All the rest burned to cinders, those fine fellows, Rennell! You were thrown unconscious, but none of my tough old bones were hurt. They pulled us out of the wreckage and brought us in here and tied us with these silver chains."

"In here? But where are we?" demanded Dick, trying to pass his hand across his aching forehead, and realizing that the chain, though it seemed fastened to nothing, was perfectly taut.

* * * * *

"In one of their damned invisible houses," whimpered the old man. "They're fireproof. Nearly all our bombs fell on the tarmac, and they did hardly any damage at all. One of those devils was bragging about it to me. I couldn't see anything but his eyes. And they've taken away my gas-box," wailed old Luke.

Dick cursed comprehensively and was silent. The burning rage that filled him left him incapable of other utterance. Silver chains! They must be madmen—yes, that was the only explanation. Madmen who had escaped from somewhere, obtained possession of scientific secrets, and banded themselves together to overcome the world. If he could get the chance of a blow at them before he died!

He heard a door swing open—a door somewhere out on the prairie. Two men sprang into sudden visibility and approached him. There was nothing invisible about these men, though they had seemed to have materialized out of nothing. They wore the same black, trimly fitting uniform that Dick had seen in the White House. They were flesh and blood human beings like themselves.

"I congratulate you upon your recovery, Captain Rennell," remarked one of them with ironical politeness. "Also upon your shrewd coup. Needless to say, it had no chance of success, but we were misinformed as to the hour at which you might be expected. We thought it would take the fools at Washington a little longer to puzzle out our location—and then we did not put quite sufficient force into our hurricane. Quite an artificial one, Captain."

Dick, glaring at them, said nothing, and the one who had spoken turned to his companion, laughing, and said something in a foreign language that he did not recognize.

"His Majesty the Emperor commands your presence, and that of this old fool," said the first man. "Do not attempt to escape us. Death will be instantaneous." He drew a glass rod from his pocket, the tip of which glowed with a pale blue light.

* * * * *

Again he spoke to his companion, who moved apparently a few feet distant out on the prairie. Suddenly Dick saw old Evans' chain slacken: then Dick's slackened too. He understood that he was unbound, though his wrists and ankles were still loosely fastened.

The second man took his station beside Luke Evans and motioned to him to rise. The first man beckoned to Dick to do the same. The two prisoners got upon their feet, trailing each a length of clanking chain. Each of the two guards covered his captive with the glass rod and motioned to him to precede him.

Choking with fury, Dick obeyed. He had taken a dozen steps with his guard uttered a sharp command to halt, at the same time shouting some word of command.

The edge of a door appeared, also seeming to materialize out of space. It widened, and Dick realized that he was looking at the unpainted inner side of a door whose outside was invisible. Beyond the door appeared a flight of steps.

Dick passed through and descended them. He counted fifteen. He emerged into a timbered underground passage, well lit with lamps, filled with what seemed to be mercury vapor. Behind him walked his guard: behind the guard he heard Luke Evans shambling. Both chains were clinking, and again Dick's fury almost overcame him.

He controlled himself. He had no hope or desire for life, but he meant to strike some sort of blow before he died, if it were possible.

They turned out of the timbered passage, Dick's guard now walking at his side, the glass rod menacing his back. Dick found himself in a large subterranean room of extraordinary character. The walls were not merely timbered, but paneled. Pictures hung upon them, there were soft rugs underfoot, there was antique furniture. Everything was in plain sight.

* * * * *

There was a door at the farther end, from beyond which came the murmur of voices. Two guards in the same black uniform, but without the ornamental silver braid, stood to attention, long halberds in their hands. One spoke a challenge.

The guard at Dick's side answered. The two men stepped backward, each about two feet, and pulled the two cords on either side of a curtain behind the open door. Dick passed through.

He stopped in sheer amazement. The gorgeousness of this larger room into which he entered was almost stupefying. It seemed to have been lifted bodily from some European palace. Mirrors with gilt edges ran along the side. On the floor was a single huge rug of Oriental weave.

At the farther end was a throne of gilt, lined with red velvet in which sat a man. An old man, of perhaps eighty years, with a grey peaked beard and fierce, commanding features. On his head was a gold crown glittering with gems. About him were gathered some twoscore men and a few women.

Those ranged on either side of the throne wore, like its occupant, robes of red, lined with ermine. The rank behind wore shorter robes, less decorative, but no less extraordinary. They might all have stepped out of some medieval court.

Behind this second line, and half-encircling them, were officers in the black uniform with the silver braid.

There had been chattering, but as Dick passed through into the room it was succeeded by complete silence. Dick fixed his eyes upon the old man on the throne.

He knew him! Knew him for a once famous European ruler who had lost his throne in the war. A man always of unbalanced mentality, who, after living for years in exile, had been reported dead three years before. A madman who had vanished to make this last attempt upon the world, aided and abetted by the secret group of nobles who had surrounded him in the days of his pomp and power.

* * * * *

Old men, all of those in the first line! Madmen too, perhaps, as madness begets madness. Behind them, younger men, infected by the strange malady, and enthusiastic for their desperate cause.

Yes, Dick knew this Invisible Emperor, lurking here in his underground palace. He knew Von Kettler, too, in the second line, close to the Emperor's throne. And, among the women in their robes, grouped picturesquely about that throne, he knew Fredegonde Valmy.

Dark-haired beneath her coronet, of radiant beauty, she fixed her eyes upon Dick's. Not a muscle of her face quivered.

Then only did Dick see something else, which he had not hitherto observed, owing to its concealment by the robes of those grouped about the Emperor, and the sight of it sent such a thrill of fury through him that he stood where he was, unable to speak or move a muscle.

The throne was set on a sort of dais, with three steps in front of it. The lowest of these steps was hollow. Within this hollow appeared the head and shoulders of a man.

An elderly man clothed in parti-colored red and yellow, the time-honored garment of court fools. He was on his hands and knees, and the round of his back fitted into the hollow of the step, and had a flat board over it, so that the Emperor, in ascending his throne, would place his foot upon it.

He was kept in that position with heavy chains of what looked like gold, which passed about his neck and arms, and fitted into heavy gold staples in the wood. And the old man was President Hargreaves of the United States!

* * * * *

The President of the American Republic, chained as a footstool for the Invisible Emperor, the madman who defied the world. Dick stood petrified, staring into the mild face of the old man, still incapable of speech. Then a herald, carrying a long trumpet, to which a square banner was attached, strode forward from one side of the grotesque assemblage.

"Dog, on your knees when His Majesty deigns to admit you to the Presence!" he shouted.

The guard at Dick's side prodded him with his glass rod.

Then the storm of mad fury in Dick's heart released limbs and voice. The cry that came from his lips was like nothing human. He leaped upon the guard with a swift uppercut that sent him sprawling.

The glass rod slipped from his hands to the rug, striking the edge of his shoe, and broke to fragments. A single streak of fire shot from it, blasting a black streak across the Oriental rug.

Dick leaped toward the throne, and the assemblage, as if paralyzed by his sudden maneuver, remained watching him without moving. Then a woman screamed, and instantly the picturesque gathering had dissolved into a mob placing itself about the person of the Emperor, who sprang from his throne in agitation.

Dick was almost at the steps. But it was not at the Emperor that he leaped. He sprang to Hargreaves's side. "Mr. President, I'm an American," he babbled. "We've located this gang, we'll blow them off the face of the earth. In chains—God, in chains, sir—"

Dick stumbled over the length of his own chain that he had been dragging behind him—stumbled and fell prone upon the floor. Before he could regain his feet they were upon him.

* * * * *

A dozen men were holding him, despite his mad, frenzied struggles, and as, at length, he paused, exhausted, one of them, covering his head with a glass rod, looked up at the Emperor, who had resumed his seat.

Dick calmed himself. Still gripped, he straightened his body, and gave the mad monarch back look for look. For a moment the two men regarded each other. Then a peal of laughter broke from the Invisible Emperor's lips. And any one who heard that peal—any one save those accustomed to him—might have known that it was a madman's laughter.

He flung back his head and laughed, and the whole crowd laughed too. All those sycophants roared and chuckled—all except Fredegonde. It was not till afterward that Dick remembered that.

He stood up. "Dog of an American," he roared, "do you know why you were brought here? It was because I wanted one Yankee to live and see the irresistible powers that I exercise, so that he can go back and report on them to those fools in Washington who still think they can defy me, the messenger of the All-Highest.

"I tell you that the things I have done are nothing in comparison with the things that I have yet to do, if your insane government of pig-headed fools persists in its defiance. It is my plan to send you back to tell them that their President lies bound in gold chains as my footstool. That the hurricane which spread the gas through southern America was a mere summer zephyr in comparison with the storm that I shall send next.

* * * * *

"All the resources of Nature are at my command thanks to the illustrious chemists who have been secretly working for the past ten years to serve me. I, the All-Highest, have been commanded by the Almighty to scourge the world for its insolence in rejecting me, and especially the pig-race of Yankees whose pride has grown so great. Mine is the divinely appointed task to cast down your ridiculous democracies and re-establish the divine world-order of an Emperor and his nobility.

"That is why I have chosen, to permit so mean a thing as you to live. As for the old fool beside you, who thought to stay my power with his box of tricks—his gas-box is already being analyzed by my chemists, and in a few hours the trivial secret will be at my disposal."

"And that's just where you're wrong," piped old Luke Evans in his cracked voice. "That gas can't be analyzed, because it contains an unknown isotope, and, as for yourself, you're nothing but a daft old fool, with your tin-horn trumpery!"

For a moment the Emperor stood like a statue, staring at old Luke. The expression on his face was that of a madman, but a madman through whose brain a straggling ray of realization has dawned. It was the look upon his face that held the whole assemblage spellbound. Then suddenly came intervention.

Through a doorway in the side of the hall came one of the officers in black. He advanced to the foot of the throne and made a deep, hurried bow, speaking rapidly in some language incomprehensible to Dick.

The Emperor started, and then a peal of laughter left his lips.

"Pig of a Yankee," he shouted to Dick, "your contemptible navy's now approaching our shores, with a dirigible scout above it. You shall now see how I deal with such swine!"

CHAPTER X

The Tricks of the Trade

He barked a command, and instantly Dick was seized by two of the guards, one of whom—the one Dick had knocked down—took the occasion to administer a buffeting in the process of overcoming him. For the sight of the honored President of the United States—that kindly old man straining his eyes to meet Dick's own—in the parti-colored garb of red and yellow, and chained like a beast below the madman's throne, again filled Dick with a fury beyond all control.

It was only when he had been half-stunned again by the vicious blows of his captors, delivered with short truncheons of heavy wood, that at length he desisted from his futile struggle.

With swimming eyes he looked upon the gathering about the throne, which, again taking its cue from the madman, way roaring with laughter at his antics. And again Dick's eyes encountered those of Fredegonde Valmy.

The girl was not smiling. She was looking straight at him, and for a moment it seemed to Dick as if he read some message in her eyes.

Only for an instant that idea flashed through his mind. He was in no mood to receive messages. As he stood panting like a wild beast at bay, suddenly a filmy substance was thrown over his head from behind. Then, as his face emerged, and the rest of his body was swiftly enveloped, he realized what was happening.

They had thrown over him one of the invisible garments. He could feel the stuff about him, but he could no longer see his own body or limbs.

From his own ken, Dick Rennell had vanished utterly. Where his legs and feet should have been, there was only the rug, with the burn from the glass tube. He raised one arm and could not see arm or fingers.

In another moment invisible cords had been flung around him. Dick's efforts to renew the struggle were quickly cut short. Trussed helplessly, he could only stand glaring at the madman rocking with laughter upon his tinsel throne. Beside him, similarly bound, stood Luke Evans, but Dick was only conscious of the old man's presence by reason of the short, rasping, emphatic curses that broke from his lips.

* * * * *

The Emperor turned on his throne and beckoned to Von Kettler, who approached with a deferential bow.

"Nobility, we charge you with the care of these two prisoners," he addressed him. "Have the old one removed to the laboratory, and give orders that he shall assist our chemists to the best of his power in their analysis of the black gas. As for the other, take him up to the central office, and show him how we deal with Yankees and all other pigs. Show him everything, so that he may take back a correct account of our irresistible powers when we dismiss him."

"Come!" barked one of the guards in Dick's ear.

Dick attempted no further resistance. Convinced of its futility, sick and reeling from the blows he had received, he accompanied his captors quietly. There was nothing more that he could do, either for President Hargreaves or for old Luke, but he still imagined the possibility of somehow warning the approaching fleet or the occupants of the dirigible.

He was led along the passage, past the guards, and up the stairs again. The top door opened upon vacancy; it closed, and vanished. Dick felt the rugs beneath his feet, but he was to all appearances standing on a square of bare earth in the middle of a prairie.

"Come!" barked the guard again, and Dick accompanied him, trailing his silver chain. Behind came Von Kettler.

"Here are steps!" said the guard, after they had proceeded a short distance.

Dick stumbled against the lowest step of an invisible flight. The breeze was cut off, showing that they had entered a building. Underneath was a large oval of bare ground. Dick found a handrail and groped his way up around a spiral staircase, four flights of it.

"Here is a room!"

* * * * *

Dick saw that widening edge of door again. The room inside was perfectly visible, though it seemed to be supported upon air. It was a spheroid, of huge size, with a number of large windows set into the walls, and it was filled with machinery. About a dozen workmen in blue blouses were moving to and fro, attending to what appeared to be a number of enormous dynamos, but there were other apparatus of whose significance Dick was ignorant. The dynamos were whirring with intense velocity, but not the slightest sound was audible.

Von Kettler stepped to a switch attached to a stanchion of white metal, surmounted by a huge opaque glass dome, and threw it over. Instantly the hum and whir of machinery became audible, the sound of footsteps, the voices of the workmen, and the creak of boards beneath their feet.

"You see, we have discovered the means of destroying sound waves as well as shadows, and it was a much simpler feat," said Von Kettler with a sneer. "Tell them that when you get back to Washington, Yankee pig. Also you might be interested to know that most of your bombs fell on camouflaged structures that we had erected with the intention of deceiving you."

He gestured to Dick to precede him, and halted him at a plain round iron pipe or rod that rose up through the floor and passed through the roof. It was surrounded by a mesh of fine wire. Attached to it were various gauges, with dials showing red and black numbers.

"This is perhaps our greatest achievement, swine," remarked Von Kettler, affably. "You shall see its operations from above." He pointed to a narrow spiral staircase rising at the far end of the room. "It is the practical application of Einstein's gravitation and electricity in field relation. It is by means of this, and the three dynamos on the ground that we were able to neutralize your engines last night and bring them down where we wanted them. You must be sure to tell the Washington hogs about that."

* * * * *

He motioned to Dick to cross the room and ascend the spiral staircase. Following him, he flung another switch similar to the first one, and instantly all sound within the room was cut off.

They ascended the winding flight and emerged upon a floor or platform. Dick felt it under his feet, but he could see nothing except the ground, far beneath him. He seemed to be suspended in the void. He stopped, groping, hesitating to advance. Von Kettler's jarring laugh grated on his ears.

"Don't be afraid, swine," he jeered. "This place is enclosed. There is a shadow-breaking device on every floor, which renders us complete masters of camouflage."

A switch snapped. Dick found himself instantly in a rotunda, roofed with glass, sections of which were raised to a height of three or four feet from the wooden base, admitting a gentle breeze. Three or four men were moving about in it, but these wore the black uniform with the silver braid, and Von Kettler's manner was deferential as he addressed them, jerking his hand contemptuously toward Dick. Grins of derision and malice appeared on all the faces.

Save one, an elderly officer, apparently of high rank, who came forward and raised his hand to the salute.

"Captain Rennell," he said, "we are at war with your nation, but we are also, I hope, gentlemen." He turned to Von Kettler. "Is it seemly," he asked, "that an officer of the American army should be brought here in chains and cords?"

"Excellency, it is His Majesty's command," responded Von Kettler, with a servile smirk that hardly concealed his elation. "Moreover, the American is to witness the forthcoming destruction of the Yankee fleet."

The elderly officer reddened, turned away without replying. Dick looked about him.

* * * * *

There was less machinery in this room. The iron pillar that he had seen came through the floor and terminated some five feet above it in another of the opaque glass domes, filled with iridescent fire. About it was a complicated arrangement of dials and gauges.

In the centre of the room was a sort of camera obscura. A large hood projected above a flat table, and an officer was half-concealed beneath it, apparently studying the table busily.

"Come, American, you shall see your navy on its way to destruction," said Von Kettler, beckoning Dick within the hood.

The officer stepped from the table, whose top was a sheet of silvered glass, leaving Von Kettler and Dick in front of it. Dick looked. At first he could see nothing but the vast stretch of sea; then he began to make out tiny dots at the table's end, terminating in minute blurs that were evidently smoke from the funnels.

"Your ships," said Von Kettler, smiling. "This is the dirigible." He pointed to another dot that came into sight and disappeared almost instantly. "They are a hundred and fifty miles away. Explain to your friends in Washington that our super-telescopic sights are based upon a refraction of light that overcomes the earth's curvature. It is simple, but it happens not to have been worked out until my Master commanded it."

Dick watched those tiny dots in fascination, mentally computing. At an average speed of fifty knots an hour, the squadron's steaming rate, they should be off the coast within three hours. The dirigible would take two, if it went ahead to scout, as was almost certain.

* * * * *

Dick stepped back from beneath the hood and glanced about him. If only his arms were not bound, he might do enough damage within a few seconds to put the deadlier machinery out of commission, if only the silvered mirror. He glanced about him. Von Kettler, interpreting his thought, smiled coolly.

"You are helpless, my dear Yankee pig," he said. "But there is more to see. Oblige me by accompanying me up to the top story."

He pointed to a ladder running up beside the iron pillar through an opening in the roof, and Dick, with a shrug of the shoulders, complied. He emerged upon a small platform, apparently protruding into vacancy. Far underneath he saw the clearing, and two airplanes on the tarmac, the aviators looking like beetles from that height. He looked out to sea and saw no signs of the fleet.

"You have heard of St. Simeon Stylites, Yankee?" purred Von Kettler. "The gentleman who spent forty years of his life upon a tall pillar, in atonement for his sins? It is His Majesty's desire that you spend, not forty years, but two or three hours up here, meditating upon his grandeur, before returning to earth. It is also possible that you will witness something of considerable interest. Look out to sea!"

Dick turned his head involuntarily. He heard Von Kettler's laugh, heard the snap of a switch—then suddenly he was alone in the void.

At that snap of the switch, everything had vanished from view behind him, the building, even the platform on which he stood. His feet seemed to rest on nothing. Yet below him he could still see the airplanes, and more being wheeled out.

* * * * *

A sense of extreme physical nausea overcame him. He reeled, then managed to steady himself. He, too, was invisible to his own eyes. Involuntarily he cried out. No sound came from his lips. He stood there, invisible in an invisible, soundless void.

For what seemed an unending period he occupied himself with endeavoring to obtain the sense of balance. Then, with a great effort, he managed to loosen the cords that bound his right arm to his side. A mighty wrench, and he had slipped them up above his elbow. His right lower arm was free.

He extended it cautiously, and his hand encountered a railing. Instantly he felt more at ease. He began moving slowly around in a widening circle, and discovered that the platform was enclosed. The further side was, however, open, and he began sliding forward, foot by foot, to locate himself. Once his foot slipped over the edge, and he drew back hastily. He felt on the other side, and discovered that he was upon what seemed a plank walk, perhaps a hundred and fifty feet above the ground, with no rail on either side, and some six feet wide.

Very cautiously he shuffled his way along it. It was solid enough, although invisible, but more than once Dick walked perilously close to one edge or the other. At length he went down on his hands and knees, and proceeded, crawling, until his movements were arrested by what was unmistakably a door.

The plank bridge, then, connected the top stories of two buildings, but what the second was, there was no means of knowing. The door was barred on the other side, and did not yield an iota to Dick's cautious pressure. Dick felt the frame. Beyond was glass, reinforced with iron on the outside, the latter metal forming a sort of lattice work. Cautiously Dick began to crawl up the rounded dome.

* * * * *

Foot by foot he made his way, clinging to the iron bars, until he felt that he had reached the point of the dome's maximum convexity. He wedged his feet against a bar and rested. Only now was it brought home to him that it would be impossible for him to find his way back to the plank.

A long time must have passed, for, looking out to sea, he could see the squadron now, minute points on the horizon, exuding smudges of smoke. The dirigible was still invisible. The airplanes had either left the tarmac or had been wrapped in the gas-impregnated cloth, for both they and the aviators had vanished.

Suddenly Dick had an odd sensation that the iron was growing warm.

In another moment or two he had no doubt of it. The iron bar he clutched was distinctly warm; it was growing hot. He shifted his grasp to the adjacent bar and even in that moment the heat had increased perceptibly.

Suddenly there came a vibration, a sense of movement. Dick was being swung outward. The whole dome seemed to be dropping into space. He dug his feet and fingers under the hot rods, and felt himself sliding over on his back.

Back—back, till he was lying horizontally in space, and clutching desperately at the iron bar, which was growing hotter every moment.

The sliding movement ceased. It was as if the whole upper section of the glass dome had opened outward. But the heat of the bars was becoming unbearable, and gusts of hot air seemed to be proceeding from within.

Hot or not, Dick's only alternative was to work his way back to the stable portion of the dome, or to frizzle until he dropped through space.

Clinging desperately to the bars, he began working back, reaching from bar to bar with his right hand and dragging his feet, with the clanking chain attached, from bar to bar also.

* * * * *

How he gained the base of the dome he was never able afterward to understand. The heat had grown intolerable; his hands were blistering. Somehow he reached it. He rested a moment despite the heat. But to find the plank walk was clearly impossible. In another minute he must drop. Better that than to fry there like St. Lawrence on his griddle.

And then, just when he had resigned himself to that last drop, there came an unexpected diversion. Almost beside him a window was hung back. A man looked out. Dick saw one of the workmen in the blue blouses, and, behind him, within the dome, what seemed like an empty room.

Dick was slightly above the man. As his head and shoulders appeared, he let himself go, landing squarely across his back. He slid down his shoulders through the open window into the interior of the dome.

The man, flung against the frame of the window by the shock, uttered a piercing cry. Before he could recover his stand, or take in what had happened to him, Dick had gained his feet and leaped upon him. His right hand closed upon his throat. He bore him to the floor and choked him into insensibility.

CHAPTER XI

In the Laboratory

Not until the man's struggles had ceased, and he lay unconscious, panting, and blue in the face, did Dick release him. Then he looked about him.

Save for the workman, he was alone in a rotunda, open to the sky, and, as he had supposed, the whole upper portion of the dome had been flung back, leaving an immense aperture into which the sun was shining, flecking the interior with shafts of light. The temperature, despite the opening of the dome, must have been in excess of a hundred and twenty-five degrees.

There was nothing except an immense central shaft, up which ran a hollow pole of glass, cut off by the invisible paint at the summit of the dome. The inside of this glass pole was glowing with colored fires, and it was from this that the intolerable heat came, though its function Dick could not imagine.

One thing was clear: It was growing hotter each moment. To remain in that rotunda meant death within a brief period of time.

And there was no way out! Dick glared around him, searching the glass walls in vain. No semblance of a stairway or ladder, even. Yet the workman must have entered by some ingress—if only Dick could discover it!

He began running round the interior of the dome in the brilliant sunshine, searching frantically for that ingress. And it was growing hotter! The sweat was pouring down his face beneath the invisible garment.

Dick was vaguely aware that the silence switch had been thrown in the room, for his feet made no sound, but the knowledge was latent in his mind. Two or three times he circumnavigated the interior of the dome, like a rat in a trap.

Then suddenly he saw a section of the flooring rise in a corner, and a workman in a blue blouse appear out of the trap door.

* * * * *

He stood there, his face muscles working as he shouted for his companion, but no sound came from his lips. He looked about him, and saw the unconscious man beside the window. He started in his direction.

With a shout, Dick hurled himself toward him. And he checked himself even as he was about to leap. For he realized that the second workman neither saw nor heard him.

Yet some subconscious impression of danger must have reached his mind, for the workman stopped too, instinctively assuming an attitude of defense. Dick gathered a dozen links of his wrist-chain in his right hand, leaped and struck.

The workman crumpled to the floor, a little thread of blood creeping from his right temple.

It was the thing upon which Dick looked back afterward with less satisfaction than any other, leaving the two unconscious men in that room of death. Yet there was nothing else he could have done. He ran to the trap, and saw a ladder leading down. In a moment he had swung himself through and closed the trap behind him.

The material that lined the walls below must have had almost perfect insulating qualities, for the temperature here was no hotter than in the Bahamas on a hot summer day. Dick scrambled down the ladder and found himself in a machine-shop. Nobody was there, and tools of all sorts were lying about, as well as machinery whose purpose he did not understand. A pair of heavy pliers and a vise were sufficient to rid Dick of his wrist and ankle chains in a minute or two. With a knife he slashed the cords of invisible stuff that bound him. He stood up, cramped, but free.

He picked up an iron bar that was lying loose on a table beside a machine, and advanced to the staircase in one corner of the shop. As he approached it, another workman came running up.

* * * * *

Dick stood aside in an embrasure in the wall partly occupied by a machine. The man passed within two feet of him and never saw him. Only then did Dick quite realize that he was actually invisible.

The moment the man had passed him, Dick ran to the staircase. He descended one flight; he was half way down another when a yell of pain and imprecation came to his ears. He knew that voice: it was Luke Evans's!

With three bounds Dick reached the bottom of the stairs. He saw a large room in front of him. No mistaking the nature of this room; it was an ordinary laboratory, fitted out with the greatest elaboration, and divided into two parts by paneling. And sight and sound were on.

In the part nearer Dick three men were grouped about a large dynamo, which was sending out a high, musical note as it spun. Levers and dials were all about it, and above it was the base of the glass tube that Dick had seen above. In the other part were five or six men. Three of them were testing some substance at a table; three more were gathered about old Luke Evans, whose silver chains had been removed and replaced by ropes, which bound his limbs, and also bound him to a heavy chair, which seemed to be affixed to the ground. One of the three had a piece of metal in a pair of long-handled pliers. It was white hot, and a white electric spark that shot to and fro between two terminals close by, showed where it had been heated.

Dick started; he recognized one of the three men as Von Kettler. He moved slowly forward, very softly, his feet making no sound on the fiber matting that covered the floor.

* * * * *

"Did that feel good, American swine?" asked Von Kettler softly, and Dick saw, with horror, a red weal on the old man's forehead. "Now you are perhaps in a more gracious mood, Professor? The unknown isotope in that black gas of yours—you are disposed to give us the chemical formula?"

"I'll see you in hell first," raved old Luke Evans, writhing in his chair.

Von Kettler turned to the man holding the white-hot metal, and nodded. But at that moment a door behind Evans's chair opened, and Fredegonde Valmy appeared in the entrance. Von Kettler turned hastily, snatched the pliers from the man's hand, and laid the metal in a receptacle.

But the girl had seen the action. She looked at the weal on Luke's forehead, and clenched her hands; her eyes dilated with horror.

"You have been torturing him, Hugo!" she cried.

"Freda, what are you doing in here? Oblige me by withdrawing immediately!" cried Von Kettler.

"Where is Captain Rennell?" the girl retorted. "I will know!"

"He is upstairs, watching the approaching Yankee fleet, and waiting to see its destruction," returned the other.

"You are lying to me! He has been killed, and this old man has been tortured!" cried Fredegonde. "I tell you, Hugo Von Kettler, you are no longer a half-brother of mine! I am through with you!"

"Unfortunately," sneered Von Kettler, "it is not possible to dispose of a family relationship so easily."

* * * * *

"It is cheap to sneer," the girl retorted. "But you sang a very different song when you were in the penitentiary, in terror of death, and you begged me to come and throw you the invisible robe through the bars. You promised me then that you would abandon this mad enterprise and come away with me. You swore it!"

"I have sworn allegiance to my Emperor, and that comes first," retorted Von Kettler. "Oblige me by retiring."

"I shall do nothing of the sort," cried the girl hysterically. "When you used me as a tool in your enterprises in Washington, you played upon my patriotism for my conquered country. I thought I was undertaking a heroic act. I didn't dream of the villainy, the cold-blooded murder that was to be wrought.

"You've kept me here virtually a prisoner," she went on, with rising violence, "an attendant upon that old madman, your Emperor, and his sham court, while more murder is being planned. Where is Captain Rennell, I say?" She stamped her foot. "I demand that he and this old man be set at liberty at once. Hugo," she pleaded, "come away with me. Don't you see what the end must be? This is no heroic enterprise, it is wholesale murder that will arouse the conscience of civilized mankind against you! Order that the vortex-ray be turned off," she went on, looking through the opening in the partition toward the dynamo. "That gas—you cannot be so vile as to send it forth again, to destroy the American ships?"

"My dear Freda," retorted the young man coolly, "the vortex-ray is already charged with the gas, and at a height of twenty thousand feet it is now creating a vacuum that will send the gas upon the wings of a hurricane straight up the Atlantic seaboard. It will obliterate every living thing on board the battleships, from men to rats, and this time we mean to reach New York.

"As for that swine Rennell," he went on, "you heard His Majesty announce his intention of sending him back to Washington with the information of our irresistible power. Of course I know you are in love with him, and that these qualms of conscience are due to that circumstance."

* * * * *

But Dick hardly heard the latter part of Von Kettler's remarks. Suddenly the significance of the dynamo and the superheated room above had come home to him. He had read of such a project years before, in some newspaper, and had forgotten about it until that moment.

By sending a high-tension current almost to the limits of the earth's atmosphere, the article had said, a vortex or vacuum could be set up which would create a hurricane.

The tremendous pressure of the in-rushing air would make a veritable cyclone, which, taking the course of the prevailing winds, would rush forth on a mission of widespread disaster.

And on this hurricane would go the deadly gas, infinitely diluted, and yet deadly to all life in its infinitesimal proportion to the atmosphere.

And the American fleet was now approaching the Bahama shores.

Dick forgot Luke Evans, everything else, as the significance of that mechanism in the next room came home to him. He ran like a madman through the space in the partition, and, raising the bar aloft, brought it thudding down upon the dials, twisting and warping them.

He struck at the hollow pole, but, glass or not, it defied all his efforts. He seized a heavy lever and flung it into reverse—and two others.

Yelling, the three attendants broke and ran. Out of the laboratory the six came running, collided with the three. Behind them Dick could see Fredegonde Valmy, a knife in her hand, slashing at Luke Evans's bonds.

Dick swung his bar and brought it crashing down on a head, felling the man like a log. He saw Von Kettler pull one of the glass rods from his pocket and fire blindly. The discharge struck a second attendant, and the man dropped screeching, his clothes ablaze.

Somebody yelled, "He's there! Look at his eyes!" and pointed at Dick's face.

* * * * *

Dick leaped aside and swung the rod again, felling a third man. The others turned and ran. Von Kettler in the van, broke through the door behind Luke Evans's chair, and disappeared.

Dick ran back to where the old man was standing beside the girl, the discarded ropes at his feet. He flung his hood back. "Luke, don't you know me?" he shouted.

It was creditable to Luke Evans's composure that, though Dick must have presented the aspect of nothing more than a face floating in the air, he retained his composure.

"Sure I know you, Rennell," replied the old man. "And you and me's going to best them devils yet."

"But the fleet—it's approaching Abaco," Dick cried. "I've got to warn them."

Fredegonde seized him by the arm.

"Come with me," she cried. "If they find you here, they'll kill you."

Dick hesitated only a moment, then followed the girl as she dashed for another door on the same side of the laboratory as that by which Von Kettler and his men had fled. They dashed down the staircase, and a corridor disclosed itself at the bottom. The girl stopped.

"There is a private way—the Emperor's," she panted. "He had it constructed—in case of necessity. I got the keys. I was planning—something desperate—to stop these murders; I didn't know what."

Dick seized her by the arm. "What keys?" he demanded. "The key to the place where President Hargreaves is?"

"Yes, but—"

"We must get him. Where is he?"

"In a cell beneath the throne room. That's overhead. But they'll catch us—"

"Which is the key?" asked Dick.

The girl produced three or four keys, fumbled with them, handed one to Dick. "This way!" she cried.

* * * * *

They ran along the corridor. Two guards appeared, moving toward them under the electric lights. At the sight of the girl running, and Luke Evans, they stopped in surprise.

Dick had pulled the hood back over his head. He ran toward them, wielding the iron bar. A mighty swing sent the two toppling over, one unconscious, the other bruised and yelling loudly.

"Here! Here!" gasped Fredegonde, stopping before a door.

Dick fitted the key to the lock and turned it. Inside, upon a quite visible bed, sat President Hargreaves, unchained. He looked up inquiringly as the three entered.

"Mr. President," said Dick, throwing back his hood, "I'm an American officer, and I want to save you. There's not much chance, but, if you'll come with me—"

Hargreaves got up and smiled. "I'm not a military man, sir," he answered, "but I'm ready to take that chance rather than—"

He did not complete the sentence. Shouts echoed along the corridor behind them. Dick replaced his hood, handed the keys back to the girl. "Take Mr. Hargreaves to any place of temporary safety you can," he said. "And Mr. Evans. I'll hold them!"

"It's right here. This door!" panted the girl, indicating a door at the end of the passage.

The three ran toward it. Dick turned. Five or six guards with Von Kettler at their head, were running toward him. They saw the three fugitives and set up a shout.

Dick had a quick inspiration. He dashed back into the cell, seized the light bed, and dragged it through the doorway into the passage, just in time to send Von Kettler and two others sprawling. He brought down the bar upon the head of one of them, shouting as he did so.

Then he became aware that the passage was flooded with sunshine. Fredegonde had got the door open.

He darted back, passed through in the wake of the three, and slammed it shut. Fredegonde turned the key. Instantly Dick found himself with his three companions upon the prairie. Not a vestige of the buildings was apparent anywhere, except for the patches of brown earth.

CHAPTER XII

Von Kettler's End

Fredegonde took command, repressing her agitation with a visible effort. "They cannot break down that door," she said, "and they dare not ask for another key. It will take them a minute or two to go back and reach us around the building. But there may be a score of people watching us. Let us walk quietly toward the thickets. If I am present, they will not suspect anything is wrong."

But Dick stood still, driven into absolute immobility by the conflicting claims of duty. For overhead, high in the blue, was an American dirigible.

And at his side was the President of the United States. One or other of them he must sacrifice.

He chose. He ran forward without answering. Those squares of brown earth, set side by side, were the airplane hangars, and he meant to seize an airplane, if he could find one beneath its coat of invisibility, and fly to warn the dirigible and the fleet.

A curious wind was blowing. It seemed to come swirling downward, as no wind that Dick had ever known. It was growing in violence each moment, beating upon his face.

As he ran, he was aware of Luke beside him. He heard shouting all about them. Luke had been seen. Not only Luke, but Hargreaves, who was running after Luke, with Fredegonde trying in vain to change his intentions. At the edge of the first brown patch Dick collided violently with the wall of the invisible hangar, and went reeling back. The shouts were growing louder.

"Wait!" gasped Luke Evans. He had something like a large watch in his hand. He held it out like a pistol, and from it projected a beam of the black gas.

Then Dick remembered Colonel Stopford's words: "He showed me a watch and said the salvation of the world was inside the case. I thought him insane."

* * * * *

Insane or not, old Luke Evans had concealed the tiny model of the camera-box to good purpose. As he swept the black beam around him, the whole mass of buildings sprang into luminosity, the figures of a score of men, grouped together, and advancing in a threatening mass, some distance away—and more.

Two airplanes, standing side by side upon the tarmac, just in front of the hangar—not mere pursuit planes, but six-seaters, formidably armed, with central turrets and bow and rear guns, and propellers revolving.

Two mechanics stood staring in the direction of the little group.

"I'm with you," gasped Hargreaves. "I'm not a military man, but I've got fighting blood, and I come of a fighting race."

Dick leaped and once more swung the iron bar. The nearer of the two mechanics went down like lead, the second, seeing his companion bludgeoned out of the air, turned and ran.

Dick shouted, pointing. Fredegonde jumped into the plane, and the President scrambled in behind her. The group, dismayed by the black beam, which Luke Evans was now turning steadily upon them, had halted irresolutely. But suddenly a head appeared, moving swiftly through the air toward the plane. It was Von Kettler, with hood flung back, the face distorted with rage and fury.

At his yells, the whole crowd started forward. Dick leaped into the central cockpit, swung the helicopter lever. Something spitted past his face, and a long streak appeared on the turret, where the gas-paint had been scored. But he was rising, rising into that increasing wind....

* * * * *

He heard a yell of triumph behind him. And that yell of Von Kettler's was his undoing. There is the telepathy between close friends, but there is also telepathic sympathy between enemies, and in an instant Dick understood what that shout of triumph portended.

He was rising into the line of magnetic force that would anchor his airplane helplessly, and leave it to be jerked down and held at Von Kettler's mercy.

He released the helicopter lever and opened throttle wide. For an instant the heavy plane hung dangerously at its low elevation, threatening to nose over. Then Dick regained control, and was winging away toward the sea, while yells of baffled fury from behind indicated the chagrin of his enemies.

He glanced up. Thank heaven the dirigible had not approached the trap. It was apparently circling overhead. Of course the observers had seen nothing, had no conception that the headquarters of the Invisible Empire lay below.

And yet it seemed to be drifting aimlessly back toward the fleet—erratically, as if not under complete control. And Dick could see the ships about a mile offshore, apparently drifting too. They were moving as no American squadron ever moved since the day the first hull was launched, for some of them, turned bow inward toward others, seemed upon the point of collision, while others were lagging on the edge of the formation, as if pointing for home.

Then suddenly the awful truth dawned upon Dick. The occupants of ships and dirigible alike had been overcome by the deadly gas.

* * * * *

Dick banked, turned, leaned forward and shouted to Luke Evans, and, when the old man turned his head, indicated to him to sweep the tarmac with his ray.

The thread of black, broadening into a truncated cone, revealed nothing save the luminous outlines of the buildings. Apparently the tarmac was deserted. It was queer, too, that the silence of the night before was gone. Dick shouted again, to assure himself of what he knew already, and heard his own voice again.

Something had happened, something unexpected——or perhaps the crew of the Invisible Emperor, satisfied with the effects of the deadly gas, had not thought it necessary to go to any further trouble.

Suddenly Dick discovered that he was almost within the circle of the line of magnetic force. Hurriedly he threw over the stick and kicked rudder. It was not till he was again approaching the seashore that it occurred to him that the force, too, was not in operation.

He opened throttle wide and shot seaward. He must ascertain what had happened, and, if not too late, give warning without delay.

Then suddenly the vicious rattle of gunfire sounded in Dick's ears, and, materializing out of the sky, came Von Kettler's face. Startled for an instant, Dick quickly realized that it was Von Kettler in his plane, with his hood thrown back.

And Dick realized that his own hood was thrown back. Two faces and nothing else, were the whole visible setting for battle.

But that look upon Von Kettler's face was even more demoniacal than before. Mad with rage at the prospective escape of his prey, and infuriated by his half-sister's appearance in the plane, Von Kettler had thrown all caution to the winds. In his insane hatred he was prepared to shoot down Dick's plane and send Fredegonde to destruction with it.

* * * * *

If Dick chose to replace his hood he would have the madman at his mercy. And, if he had thought about it, he would have done so, with Fredegonde sitting behind him. But the idea did not enter his mind. Consumed with rage almost equal to Von Kettler's, he only saw there the face of one of those who had inflicted an unspeakable outrage upon the President of his country.

The memory of old Hargreaves, chained before the mock-Emperor's throne, enraged Dick more than the holocaust of lives taken by the assassins.

He shouted a wild answer to Von Kettler's challenge as his plane sped by, and banked. At that moment there came a roaring concussion that shook the plane from prop to tail.

Dick turned his head. Somehow, President Hargreaves had contrived to get the rear gun into action, and now he was staring at it as if he could not believe that he had fired it.

And that action heartened Dick wonderfully. As Von Kettler's face appeared again, he loosed his turret gun in a sweeping blast, and heard Von Kettler's gun roar futilely.

Again they crossed each other's path, and again and again, two faces, only able to gauge roughly the position of their planes. Neither man had succeeded in injuring the other.

Once old Lake turned his black ray upon Von Kettler, and for, a moment the plane stood out luminously in the blackness, but Dick leaned forward and yelled to the old man to desist.

And once Dick looked back and saw Fredegonde crouched in her cockpit with eyes wide with terror. And yet he read in her eyes the same determination she had expressed in the laboratory. She was through with her half-brother.

* * * * *

All this while the wind had been increasing, making it difficult to maneuver the heavy plane; but now, of a sudden there came a dead lull, and then, with a whining sound, the wind rushed in again.

But this was a wind still more unlike any that Dick had ever known. A mighty gale that revolved circularly, but downward too, like a vortex, catching the plane and sweeping it into an ever tightening circle.

A man-made gale, upon whose wings the poison gas would spread northward again, carrying unlimited destruction with it. Dick fought in vain to free himself.

He was revolving as in a whirlpool, and it required the utmost presence of mind and watchfulness to hold the plane steady. Round and round he spun—and then, suddenly, out of the void materialized Von Kettler's face.

Von Kettler, helpless too, was spinning round upon the opposite side of the vortex. Thus each airship was upon the tail of the other, and it was a matter of chance which would get the other within the ringsights of the turret gun.

Von Kettler was so near that his shouts of fury came fitfully to Dick's ears as the wind carried them. Dick, working the controls, knew that not for an instant could he direct his attention from them in order to fire his gun, and the moment Von Kettler attempted to do so, he was doomed.

Round and round, struggling, battling in vain—and once more the concussion of the rear gun shook the plane. And a shout from the President reached Dick's ears.

Dick turned his head for an instant, long enough to see Von Kettler spinning down through the vortex. And he was going down afire. President Hargreaves, "no military man," had got him, the second time he had ever aligned a gun-barrel upon a target.

"Bravo, sir, bravo!" Dick shouted.

And desperately he flung the stick forward and nosed down.

* * * * *

No gale, man-made or heaven-made, could carry on its wings three-quarters of a ton of armored, turreted airship. Swirling like a leaf, the plane broke through the clutch of the blast. Instantly it grew calm. Outside that vortex, hardly a breath of air was stirring. It was as if the whole fury of the air was concentrated within that circle.

The ground came rushing up. Once more Dick tried to head seaward. With flying speed lost, he was calculating the exact moment in his downward rush when he could hope to resume control. Would that moment come before he crashed?

At less than a hundred feet he partly regained control. For a moment the plane seemed to fly on an even keel. Then her nose went down as her speed slackened. And this time there was no salvation.

Working desperately to save her, Dick saw the ground loom up before him. He heard the crash as the plane broke into splintering ruin ... he had a last vision of old Luke clutching his precious watch: then everything was dissolved in darkness....

CHAPTER XIII

You Can't Down the Marines

"He's pulling out of it! Keep it up, Gotch!"

Dick heard the words and opened his eyes. He stared in amazement at the faces about him. Honest American faces under tropical helmets and above a uniform that he had never expected to see again. It couldn't be real. And yet it was. One word broke from his lips:

"Marines!"

"He's got it. Don't let him slip, Gotch.", grinned one of the friendly faces, and the man named Gotch, who presumably had some qualifications for his job, continued what was meant to be a gentle massage of the nerve centers along Dick's spine.

"I'm all right." Dick muttered, beginning to realize his surroundings. He was lying on a strip of prairie near the beach, on which the waves were breaking in low ripples about a motorboat that was drawn up.

He sat up. The world was swimming about him, but he seemed to have no broken bones. Not far away was the wrecked plane, an incongruous mass of streaks where the fabric had ripped through the gas-paint. "Where are the others?" Dick muttered.

Then he was aware of Fredegonde Valmy lying with a white face under a shrub. Her eyes were open, and turned toward him.

He heard Luke Evans's voice. The old man hobbled round from Dick's back, one arm in a bandage.

"She's hurt rather bad, Rennell, but we won't know how bad till we can get her away," he said. "You've been lying here about an hour, since we crashed. President Hargreaves made them take him to the fleet in the other motorboat to see what he could do. He's assumed command.

"You see, Rennell, that damn gas caught the fleet and put pretty near every man out of commission for good. But these fellows wasn't going to give up. So, since all their officers were gone, they took two of the boats and their arms and equipment, and came ashore to settle accounts. And they won't believe there's anybody on the island or any buildings. And I can't make 'em believe it. God, Rennell, those invisible devils may attack us at any moment. I don't understand what they're waiting for."

Gotch spoke: "We know you're Captain Rennell, sir. And this gentleman, we know him too, but he seems a bit queer in his head. Talking of the Invisible Emperor's headquarters on this island, a mile or so inland. The only invisible thing we've found is that piece of a garment we pulled off you."

"I broke my watch ray machine in the fall, and I can't make them believe, Rennell," almost wept old Evans. "Tell them I'm not crazy."

Dick got upon his feet with an effort, staggered a little, then made his way to Fredegonde. He kneeled down beside the girl. She was conscious, and smiled faintly, but she could not speak. He pressed her hand, rose, and came back. "Mr. Evans is not crazy," he said. "The headquarters of the gang is over there." He pointed. "Didn't President Hargreaves tell you?"

"He was kind of incoherent, sir." The marines looked at one another, wondering. Was Captain Rennell crazy too?

"We've had scouts out through the jungle, sir. There's nothing within five miles of here. They had a clear view through to the sea from the top of a hill."

"I've been there." Dick spoke with conviction. "I must tell you they've got devices that make them practically irresistible. That gas and other things. And they're invisible. But if you boys are willing to follow me, I'll lead you. It means death. I don't know what they're waiting for. But—are you willing to follow me?"

"We'll follow you, sir"—after a pause, during which Dick read in their eyes the desire to humor a crazy man. "We'll follow to hell, sir—if that gang's really there."

"Take your arms, then!" Dick pointed to the stacked rifles.

A minute later the twenty-odd Marines, forming an open line that extended from one side of the clearing to the other, were on their way toward the headquarters of the gang. And Dick, leading them, though his head was reeling, felt as if his own reason was slipping from him. Had he only dreamed all this? Was it possible that the headquarters of the Invisible Emperor existed on this desolate prairie? If it was true, why had they suddenly become silent, inert? Why had they not long ago wiped out these few Marines? And the gale—was it now sweeping northward on its mission of destruction?

* * * * *

Half an hour passed. Then the brown patches of the foundations came into view upon the open ground. Here were the hangers, here was the central building with the Emperor's headquarters. And nothing was visible, nothing stirred, yet at any moment Dick expected the rattle of machine-gun bullets or some more terrific method of destruction.

"Halt!" The line stood still. "I am going forward ahead or you. You'll follow at a distance of twenty paces. When you see me stop, feel for the door in the wall, and if I disappear, follow me. You understand?"

The Marines assented cheerfully. No harm in humoring this poor devil of an officer who had crashed and lost his wits. Like Luke Evans, shambling up through the line to Dick's side. Dick advanced. At any moment now the concentrated fire of the Emperor's men should blast them all to smithereens. Nothing happened.

And it was no dream, for Dick's outstretched hand encountered the exterior wall of the building. He had gauged his way accurately, too, for a step or two brought him to the door. He stepped inside. He was inside the private door that led to the Emperor's quarters, through which he had passed with Fredegonde, Hargreaves, and Luke Evans in their flight. It had been broken down, contrary to the girl's predictions, and the deserted passage within was perfectly visible to them all.

Stupefied, the Marines bumped and jostled with each other as they crowded in. If they had been anything but Marines, their own heads might have been turned at the discovery of this sudden materialization of a building out of nothingness.

Being Marines, they only grinned sheepishly, and followed along the corridor.

* * * * *

The first human being they saw was one of the guards, in a black tunic. He was leaning against a wall, and he was a human being no longer. He looked as if he was asleep, but he was stone dead, with a placid look on his face.

Two more dead guards lay across each other, with smiles on their faces: and there was a workman in a blue blouse who had been in a tremendous hurry to get somewhere, from his appearance, and had never got there. He had fallen asleep instead, and never wakened.

Dick found a stairway and led the way up. He thought it ran up to the laboratory, but, instead, the room into which he emerged was the ante-room of the Invisible Emperor's audience hall. Six dead guards lay in a heap in front of the curtain, and they had died as unconcerned as their fellows, to judge by the pacific expressions on their faces.

Dick passed through into the throne room. The Marines, behind him, for the first time uttered exclamations of awe—of pity.

The terrific scene that met Dick's eyes would be burned into his brain till his last day.

Upon his throne, head flung back, sat the Invisible Emperor, his features set in a sardonic leer of death. And all about him, some sitting, some lying, supporting one another, were his court, officers in black uniforms with the silver braid, and women in court dress. And all were dead too. But they had not known they had died. They had fallen asleep—upon the instant that their own volatile gas reached them.

* * * * *

"I guess that's the explanation, sir," said old Luke Evans. "Those devils made the whirlwind and charged it with the gas. But when you reversed that lever, you reversed the process. Instead of projecting the force outwardly, you made a suction, and every atom of the gas that hadn't travelled beyond the radius came rushing back and filled the building. If we'd entered a half-hour later, we'd have been dead ones ourselves, but the gas was volatile enough to disperse through the chinks and crannies. Anyway, it's all over now."

Yes, it was all over, Dick thought, as he sat in his deck chair upon the cruiser that was bearing him northward. The menace to world government had been destroyed and with it all who had been behind it. There would be a new order in the world, a new and kindlier government. Men would feel closer to one another than in the past. Half the personnel of the fleet had escaped the invisible death, and only one cruiser and the dirigible had been lost in the confusion. There would be a great reception when they put into Charleston.

Dick bent over Fredegonde, who was asleep in her chair beside him. The ship's surgeon had promised recovery for her. She shouldn't suffer for her half-voluntary part in the business, Dick said to himself. It was going to be his task to help her to forget.

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Prisoners on the Electron

By Robert H. Leitfred

[Sidenote: Fate throws two young Earthians into desperate conflict with the primeval monsters of an electron's savage jungles.]



The blood-red glow of a slanting sun bathed the towers of New York's serrated skyline, then dropped into a molten sea beyond the winter horizon. Friday, the last day of Jupiter, the thirteenth month of the earth's new calendar, had drawn to a close. In a few hours the year of 1999 would end—at midnight, to be exact.

Far below the towers stretched well lighted canyons teeming with humanity. At an upper level where once the elevated trains had roared and rumbled in an antiquated period long past, an orderly mass of workers and shoppers was borne at an incredible speed from lower Manhattan to towering apartments that stretched northward to Peekskill. The northbound traffic was heaviest at this hour and the moving sidewalk bands were jammed to their capacity.

Street cars, now obsolete, had vanished from the streets under the new order of things as had also passenger cars, taxis and trucks. Speed predominated. Noise had practically been eliminated. Except for the gentle throb of giant motors far underground, the city was cloaked in silence.

At regular intervals along the four-speed moving bands that formed the transportation of the great metropolis, huge circular shafts of steel mounted upward beyond the roofs of the tallest buildings. Within these shafts, swift elevators carried passengers who lived in the outlying districts to the level of the station platforms of the interstate operating transport planes.

* * * * *

Close to the entrance of one of the steel shafts stood a young man a little above medium height. His deep-sunken eyes were those of a dreamer, a searcher. They were the eyes of a man who had seen strange and startling things. At present they were staring into the pulsing wave of humanity flowing northward on the endless steel bands beyond the platform.

Quite suddenly they lighted with pleasure as a man and a girl detached themselves from the swift moving river of people and hurried to the spot where he stood.

"Think we were never coming?" Karl Danzig's eyes were much like those of Aaron Carruthers. Just now they sparkled with suppressed excitement.

Aaron Carruthers smiled in turn. "No, Karl. Any man but you. I couldn't imagine you being late." He turned his attention to the slim, dark haired girl. "Nanette," he murmured, extending his hand, "I didn't think you'd come."

Dazzling white teeth caught the glow of the blue-white incandescents along the platform, and became under the bow of her red lips a string of priceless pearls.

"I had to come, Aaron. Karl has done nothing but talk of your amazing discovery. The experiment fairly frightens me at times especially when I recall the sad fate of your friend, the missing Professor Dahlgren. I wish you boys would give up the idea—"

"Nan, be still," broke in Karl, with brotherly rudeness. Turning to Carruthers. "Everything all ready, Aaron?" he asked.

* * * * *

Carruthers nodded. "As far as humanly possible. The element of error is always present. I've checked and re-checked my calculations. I've augmented the vacuum tubes by installing three super-dimensional inverse power tubes." He clasped the girl's arm. "The street is no place to talk. Let's go to the laboratory."

They crossed the moving bands by an overhead bridge and cut down a narrow canyon to the entrance of a crosstown series of bands. They stepped onto the first band. The speed was moderate. From there they moved over to the second. Carruthers was in a hurry. He guided the girl and her brother across the third to the fourth band of moving steel.

Buildings slid past them like wraiths in the electric light. They felt no winter chill, for the streets and platforms were heated by a constant flow of warm air from slots ingeniously arranged in the band of swift moving metal upon which they stood. Within a few minutes they had arrived at their destination. Quickly they reversed their path across the moving bands until they reached the disembarking platform. A short distance from the station they came to the entrance of a huge tower building.

Carruthers nodded to the doorman and they were admitted into a marble hallway. A silent, unattended lift bore them swiftly to the seventy-fifth floor. Down a deep carpeted hallway they moved. Carruthers touched his door. It opened. He stood to one side as the other two entered.

* * * * *

Nanette cried with delight at the luxurious splendor of the place. "Why, Aaron, I never dreamed the night view could be quite so delightful! I do believe that if the horrid government had not taken down that little Statue of Liberty and substituted the Shaft Triumph in its place, that I could easily see her fingers clasping the torch she was reputed to hold.

"Progress, dear girl," shrugged Carruthers, holding out his hands for her cape. "By the way, have you folks eaten?"

"Not in a week," said Karl.

"Von Sternberger's food tablets," informed the girl.

Carruthers nodded. His deep-set eyes regarded them appraisingly. "Any ill effects?"

"None whatever," spoke Danzig. "Neither of us have the slightest craving for food."

"Good. Did you bring any with you?"

"A whole carton."

"Then I guess we're already to make the experiment. You're sure. Nanette, that you're not afraid of...."

"Don't be silly, Aaron. I haven't grown up with Karl for nothing. He's always used me for the disagreeable end of his crazy experiments. And besides," she smiled on both men. "I have a woman's curiosity for the unknown."

"Very well," said Carruthers gravely. From his waistcoat pocket he took a ring of keys and inserted one of them into the lock of an immense steel door. "Our laboratory," he announced, swinging the door wide.

* * * * *

Nanette's eyes opened wide at the paneled whiteness of the room. Most of the far side was taken up with electrical machines, dynamos, generators and glass enclosed motors of an advanced type. Overhead, concealed lights made the room as light as day. A heavy glass railing shielded a square spot in the exact center of the room.

"What's that for?" asked the girl.

Danzig and Carruthers both regarded it with troubled eyes. It was Carruthers who spoke.

"That railing marks the spot where Professor Dahlgren stood when the rays of our atomic machine struck him."

"You mean," breathed the girl, "that he never moved from that spot after the rays touched his body? What happened?"

Karl had already divested himself of his coat and was checking the copper cables leading into a strange machine.

"It was rather curious," remarked Carruthers. "The moment the ray touched him his body began to dwindle. But evidently he suffered no pain. As a matter of fact his mind remained quite clear."

"How did you know?"

"As he dwindled in size," continued Carruthers, "he shouted warningly that the rays had become confused and for us to cut the switch. But the warning came a fraction of a second too late. Even as my fingers opened the contact, his body dwindled to a mere speck and disappeared entirely from sight."

* * * * *

Nanette gazed with staring eyes at the ill-fated spot. Her face had grown steadily paler. "Oh, Aaron! It's awful! What do you suppose happened?"

Carruthers eyes glowed strangely. "I didn't exactly know at the time, Nanette. I'm not sure that I know even now. But I've got a theory and Karl has helped me to build a second machine to flash a restoring ray on the square spot. What will take place I cannot even conjecture."

"Let's get on with the experiment," interrupted Karl. "Nanette can be shown later what she is to do."

Carruthers turned to Danzig. "All right. Karl. Draw up a chair to your machine. And you, Nanette, sit close to this switch. It's off now. To turn it on, simply push it forward until the copper plates slide into each other. To turn the current off, you pull sharply out. However, we aren't quite ready."

He shifted his position until he stood before a third machine slightly smaller than the other two. His fingers clicked a switch. The dial of the instrument glowed whitely.

"It's important," continued Carruthers, "that we first locate our interference. We have here, Nanette, a common television receiving apparatus capable of picking up news and pictures from any corner of the globe. Ready, Karl?"

Danzig clicked on the switch before his own machine and turned one of the many dials mounted on the panel in front of him. A faint hum filled the room as the generator settled to its task.

* * * * *

Carruthers reached up and dimmed the overhead lights. A screen of what looked like frosted glass set in the wall glowed luminously. The interior of a famous broadcasting studio became mirrored in the glass screen. Into it stepped the master of ceremonies. He spoke briefly of the New Year's activities that would soon take place when the twenty-eighth day of Jupiter ended at midnight.

"Boston," said Carruthers. "Too near."

"Try Frisco," suggested Karl. "The tubes ought to be sufficiently heated by this time."

The dial whirled beneath Carruthers slender fingers. The pictures framed in the frosted panel faded. Another took its place. San Francisco—an afternoon concert. Carruthers saw and listened for a moment, then moved thousands of miles out to sea.

Shanghai drifted into the panel, announcing in sing-song accents the weather reports. Following this came reports of various uprisings along the Manchurian border.

While yet the three listeners and watchers bent their heads toward the panel in the wall, a strange thing occurred. The silver frostiness of the screen became violently agitated with what looked like tiny sparks darting in and about each other like miniature solar systems. Shanghai faded from the picture. All that remained visible now was the jumbled mass of needle-pointed sparks of luminosity.

"Careful," warned Carruthers. "Slow up the speed of your reflector, Karl. There, that's better. Watch the meter reading. I'm going to step up the power of the dimensional tubes. Steady!"

* * * * *

From an invisible reproducer came a sharp, metallic crackling like machine-gun bullets rattling on a tin roof. The sparks on the screen became violently agitated, pushing around in erratic circles and ellipses. They glowed constantly in shades of bright green through the blues into the deep violets of the color scale.

"What do you read?" asked Carruthers.

"Point seven six nine," answered Karl.

"Shift it back towards the blue, about two points lower on the scale."

Danzig twisted two dials at the same time with minute exactness. "Point seven six eleven," he intoned.

"Hold it," ordered Carruthers. "Blue should predominate." He turned his eyes on the dancing sparks on the screen. They glowed now a deep indigo blue. "Lock your dials against accidental turning. We're tuned to the vanishing point."

Danzig rose to his feet. "What will we use?"

Carruthers looked hastily around the room. "Most anything will do." His eyes rested on a glass test tube. Quickly he rose to his feet and removed it from the wall rack. Then bending over the glass railing that enclosed the mysterious square he placed it on the floor. He turned now to the girl.

"Quiet, now, Nanette, and don't under any condition leave the chair. The path of the ray should pass within two feet of you, having a wide margin of safety. All right, Karl. Set the dials of the inverse dimensional tubes at point seven six eleven, and switch the power to the Roentgen tube."

Through the dimly lighted laboratory came a spurt of bluish flame that twisted and squirmed with slow undulations around the cathode electrode.

"Fine," enthused Carruthers, "The cathode emanations coincide exactly with the interference chart. Watch your meter gauges, Karl, while I switch to the atomic ray."

* * * * *

His fingers closed over a switch. The indigo points of flame bathing the electrode gathered themselves into a ring and began to revolve around an invisible nucleus located near the electrode. Carruthers studied the revolving flame for a moment, then switched off the television machine. It was no longer needed.

Carefully, for the atomic ray was still a mysterious force to Carruthers, he opened a small door in the panel and drew out the focusing machine. It was shaped very much like a camera except that the lens protruded several inches beyond the machine proper.

With infinite patience he made the final adjustments and moved away from the front of the lens. "Ready?"

Danzig nodded and threw on the full power of the inverse dimensional tubes. A low clear hum filled the quiet room of the laboratory. From the lens of the focusing machine shot a pale, amber beam. It struck the glass test tube squarely in the center and glowed against its smooth sides.

Carruthers reached across his own machine and turned the final switch. The amber beam emanating from the lens increased in intensity. And as it increased it took on a deep violet color.

Nanette cried out in muffled alarm. But even as Vincent raised his voice to quiet her fears the test tube suddenly shrunk to nothingness and vanished into the ether.

"Aaron!" whispered the girl, awesomely. "It ... it's gone!"

Carruthers nodded. Beads of sweat stood out upon his forehead. Would the returning ray work? He had made the test tube follow the same route as that taken by Professor Dahlgren. Both were gone. He clicked off the switch and the beam faded.

* * * * *

With a deliberate calmness that in no way matched the inner tumult brought on by the experiment, he turned the dials of the machine he and Danzig had worked out together. A second switch clicked under his fingers. From the lense of the focusing machine shot the reverse atomic beam. As it struck the center of the square it turned a bright vermilion. For several seconds it played upon empty space, then the miracle unfolded before their eyes.

Something like a glass sliver reflected the beam. It grew and enlarged under their startled eyes until it had achieved its former size, then the power that had brought it back switched itself off automatically.

Together both men examined the test tube. It appeared in no way harmed, nor did it feel either warm or cold from its trip through the elements.

"It works!" marveled Danzig. "Let's try it again with something larger."

"I've got a better idea," said Carruthers, rising to his feet. He crossed the laboratory and went to another part of his rooms. Presently he returned holding a small pink rat in his hands. The rodent was young, having been born only a week before. "Now we'll see what happens."

"Oh, it's torture to the poor thing," burst out Nanette.

"It won't hurt it," growled Karl. "Aaron knows what he's doing."

Carruthers placed the little rat in the center of the square. It lay there, very quiet and unblinking. Again the switches clicked as the contacts were closed.

Came once more the beam of amber colored light followed closely by the violet. The rat dwindled to the size of an insect, then disappeared into space. The three watchers held their breaths. Carruthers' hand trembled the least bit as he threw on the switch controlling the animal's return to the world.

* * * * *

A vermilion shaft of light pierced the semi-darkened rooms. The animal had been gone from sight not more than a minute. Abruptly something grayish white unfolded in the reflector's beam. It rapidly expanded under three pairs of bulging eyes—not the small, pinkish rat that had disappeared but sixty seconds previous, but a full grown rat, scarred and tailless as if from innumerable battles with other rats.

As the current clicked off Aaron Carruthers bent forward. Too late. The rat scurried from the laboratory with a squeal of alarm. Carruthers returned to his seat before the atomic machine and sat down. His face was worried. Dark thoughts stormed his reason. The rat he had placed within the atomic ray had aged nearly two years during the minute it was out of mortal sight. Two years!

He pulled a pad from his pocket and calculated the time that had elapsed since Professor Dahlgren had vanished from that same spot. Nearly forty hours. That would mean....

Nanette stirred in her chair. "What happened to the little rat, Aaron?"

Carruthers, busy making calculations, did not hear the question.

She turned to her brother. "Karl, what's the meaning of this? The second experiment didn't turn out like the first one. What became of that little rat?"

"I don't know what happened, Nan," spoke Karl. "Now don't bother me with your silly questions. You saw the same thing I did."

* * * * *

Carruthers raised his head and spoke quietly. "That rat you saw materialize under the atomic rays was the same rat you saw me place within the square."

"But it couldn't be," protested the girl.

"Nevertheless," shrugged Carruthers. "It was the same animal—only it had aged nearly two years during the brief time interval it was off from our planet."

"It's preposterous," cried the girl.

"Nothing is preposterous nowadays, Nanette."

"That's the woman of it," spoke Karl. "Always doubting."

"You boys are playing tricks on me," retorted the girl sharply. "I shouldn't have come to your old laboratory. Just because I'm a girl...."

"Don't," pleaded Carruthers, looking up from his pad of figures. "We're trying to solve the mystery underlying the forces which we have created." He replaced the test tube within the center of the square and returned to the atomic machine.

Through the twilight shadows of the room glowed the strange new ray. Faintly the generator hummed. Lights sparkled and twisted around the cathode in serpentine swirls.

"You needn't trouble to explain your silly experiment again," finished Nanette, rising abruptly to her feet. "I'm going home and dress for the New Year's party."

"Watch your switch like I asked you to," spoke Carruthers.

"Sit down," added Karl. "Don't put the rest of us in danger!"

"Oh-h-h!" gasped the girl as she inadvertently stepped squarely into the atomic ray of amber-colored light.

* * * * *

Carruthers leaped impatiently to his feet. An inarticulate cry of horror froze upon his lips. Forgetful that he himself was directly in line of the atomic ray he lunged forward, his mind centering on a single act—to drag the protesting and now thoroughly frightened girl out of the path of the penetrating ray.

But even as he started forward Nanette tripped over the glass railing around the square. Carruthers moved quickly. Yet his movements were slow and ungainly as compared to the speed of the light ray. He saw the figure of Nanette decrease in size before his eyes, heard the muffled expression of alarm and fear in Danzig's voice; then the room suddenly began to extend itself upward with the speed of a meteor.

What once had been walls and bare furniture resolved themselves into a range of hills, then mountains. The twilight gloom of the room became a dark void of empty space that seemed to rush past his ears like a moaning wind.

He had the sensation of falling through infinite space as if he had been propelled from the world and hurled out into the vastness of interplanetary space. Something brushed against him—something soft and fluttering. He grasped it like a drowning man would clutch a straw. "Nanette!"

The name echoed and re-echoed through his mind yet never seemed to get beyond his tightly clenched lips. He felt something cool close over his hand. Instinctively he grasped it. Her hand. Together they clung to each other as they felt themselves being hurled through endless space.

The twilight changed swiftly to black night that rushed past the two clinging figures and enveloped them in a wall of silence. Then out of the mysterious fastness came the dull glow of what looked like a distant planet. It grew and enlarged till it reached the size of a silver dollar. Little pin-points of light soon began to appear on all sides of it, very much like stars.

* * * * *

Carruthers attempted to reassure Nanette that all was well, and they were out on the streets of the great metropolis. But even as he wrenched his tightly locked lips apart he saw that the shining disc far out into space was not what he had first thought it was—the earth's moon.

He shook his head to clear it of the perplexing cobwebs. What was the matter with his mind? He couldn't think or reason. All he knew was that he had erred. This strange planet looming in the sky held nothing familiar in markings nor in respect to its relations to the stars beyond it.

While yet he groped in the darkness for something tangible, his mind reverted to the girl at his side. She was clinging to him like a frightened child. He could feel the pressure of her body against his and it thrilled him immeasurably. No longer was he the cold, calculating young man of science.

How long they remained in state of suspension while strange worlds and planets flashed into a new sky before their startled eyes, Aaron Carruthers didn't know. At times it seemed like hours, years, ages. And when he thought of the tender nearness of the girl he held so tightly within his arms, it seemed like a few minutes.

Gradually the sensation of speed and space falling began to wear off, as if they were nearing earth or some solid substance once more. The air about them grew heavier. Then all movement through space ceased.

Carruthers was surprised to find what felt like earth beneath his feet. For long minutes he stood there, unmoving, still holding possessively to the girl.

"Aaron!" The name came out of the void like a faint caress.

"Nanette."

Reassured of each other's presence they stood perfectly still, lost in the vast silence of their isolation.

* * * * *

Presently the girl spoke. "Oh, Aaron, I'm frightened!"

"There's nothing to be alarmed at, dearest." The endearing term came for the first time from the man's lips. As long as he had known Nanette Danzig, love had never been mentioned between them. If it had ever existed, the feeling had not been expressed.

"You shouldn't call me that, Aaron."

His voice sounded curiously far-off when he answered. "I couldn't help it, Nan. Our nearness, the strange darkness, and the fact that we are alone together brought strange emotions to my heart. At this moment you are the dearest—"

Bump, thump! Bump, thump!

"What's that noise?" breathed Nanette.

Carruthers turned his head to listen. To his ears came the pound of some heavy object striking the ground at well-regulated intervals.

Nanette, who had started to free herself from Carruthers violent embrace, suddenly ceased to struggle. "Oh, what is it? What is it?" she whispered fearfully.

Carruthers sniffed the night air. A musky odor assailed his nostrils, strange and unfamiliar. "It's beyond me, Nanette. Let's move away from this spot. Perhaps we can find shelter for the rest of the night."

But the Stygian blackness successfully hid any form of shelter. Tired from their search they sat down.

"We might build a fire," suggested Carruthers, "only there doesn't seem to be any wood around. Nothing but bare rock."

"Perhaps it's just as well," spoke the girl. "The fumes might attract prowlers."

"Maybe you're right," agreed Carruthers.

* * * * *

A silence fell between them. After a long time Nanette spoke.

"I don't suppose, Aaron, that anything I can do or say will help matters any. I know that our being where we are is my own fault. I'm sorry. Truly I am."

"The harm is done," said Carruthers. "Don't say anything more about it."

Nanette pointed at the disc of light shining high in the heavens. "These stars are as strange to me, Aaron, as if I had never seen them before. Saturn is the evening star at this time of year. It isn't visible. Even the familiar craters and mountains of the moon look different. And it glows strangely."

"I'd rather not talk about it, Nan."

Nanette placed a hand upon his arm. "I'm not a child, Aaron. I'm a grown woman. Fear comes through not knowing. Tell me the truth."

"Let's sit down."

They sat upon the ground and both stared out at the night heavens that arched into infinity above them. Presently Carruthers took the girl's hand from his arm and held it gently between his own. "You've guessed rightly, Nan. The orb shining upon us is not our moon. I'll try and make it clear."

* * * * *

The girl smiled reassuringly in the darkness. "I'm waiting."

"Strange as it must seem," began Carruthers, "you and I are still within the room of my laboratory. But we might as well be a million miles away for all the good it does us. Karl sits in his chair in the same position as when we disappeared in the violet glow of the atomic ray. His eyes are bulging with fear and horror. For days and days he'll continue to sit on that chair, his mind not yet attuned to what actually took place. What has happened? He doesn't know yet, Nan."

"Oh, it's incredible," sobbed Nanette.

"I know, but it's so obviously true that I won't even trouble to check my calculations." He pointed at the silver disc hanging low in the strange sky. "That, Nan, is not our moon. It is nothing more than a planetary electron very much like the one we are on at the present moment. The firmament is filled with them. From where we sit we can see but the half nearest to us. The glowing portion is illuminated from distant light rays shot off from the nucleus of the atom itself. That atom is going to be our light and heat for weeks, months, perhaps years to come. We're prisoners on an electron, and as such we are destined to rush through infinite space for the remainder of our lives unless...."

"Unless what?"

Aaron Carruthers hesitated for a bare fraction of a second. "Karl!" he whispered. "Our lives depend on him. Time flies fast for us, Nan. Already it is growing light. But not on our earth. Karl still sits upon his chair staring incredulously at the miracle of our disappearing bodies. It will take weeks of time, as it affects us, for the initial shock to travel along his nerves to the center of his brain."

* * * * *

His voice shook with emotion quite contrary to his usual calm nature. "Oh, I know it's hard to understand, Nan. I was a fool to meddle with laws of which I know so little compared to what there is yet to know."

"Then it's all true, Aaron. The little rat that came out from under the ray as an old rat was one and the same animal."

Carruthers nodded. "Time has changed in proportion to our size. We're moving so much faster than the earth that we must of necessity be bound to the universe of which we are now an integral part."

For a long time they remained silent, each immersed in dark, troubled thoughts. Nanette broke the silence.

"You don't suppose, Aaron, by any chance that Professor Dahlgren is still alive and on our planet?"

Carruthers shook his head negatively. "It's beyond human reason, Nan. He was lost in the ray for over forty hours. Translated into minutes he's been gone twenty-four hundred minutes. Since the mouse we placed within the light ray aged approximately two years in the space of one minute, Professor Dahlgren would, if he were alive, be about four thousand, eight hundred years old."

Nanette rose abruptly to her feet. "Oh bother the figures. My head's swimming with them. It's getting light now, and I'm hungry."

"Eat one of your food tablets," suggested Carruthers.

"Please don't get funny," said Nanette. "Karl has them in his coat pocket."

"Hum-m-m!" coughed Carruthers, following her example by rising to his feet. "Looks as though we'd have to rustle our food. I've got nothing on my person but a knife, a pencil, a fountain pen and some pieces of paper. Nothing very promising in any of them."