Piracy Preferred
Arcot, Morey and Wade 01.1
Amazing Stories – June 1930
(1930)*
John W. Campbell, Jr.
illustrated by WESSO

	ONCE again our young author offers us a rare combination of accurate science with excellently written fiction. It is perfectly possible to get sunburned in a dark room into which only ultra-violet rays of light-—so called—penetrate. The same rays can make some substances visible and fail to do so with others. A word can be written with a colorless, clear solution so as to be completely invisible on paper, except under the proper light. Why, therefore, is it not possible to go ahead of these phenomena and penetrate further into the secrets of invisibility and visibility. Mr. Campbell, in looking ahead to the future of aviation, propounds some ingenious ideas, always based on sound scientific fact, as to the possibilities of this most interesting of subjects—aviation. This is an excellent bit of scientific fiction.

-

	HIGH in the deep blue of the afternoon sky rode a tiny speck of glistening metal, scarce visible in the glare of the bright sun. The workers on the machines below glanced up for a moment—four twenty-one it must be—then bade to their work, though little enough it was on these automatic cultivators. Even this little break in the afternoon program was of interest in this dull monotony of green. But they would soon be starting back to the plantation city. These endless fields of castor bean plants had to be cultivated, but with the great machines that did the work it required but a few dozen men to cultivate an entire county. Indeed, so vast was the area, that little helicopters were, even now resting on the big cultivator, that they might fly back at the end of the day, leaving the machine where it was, ready to use in the morning.

	High above them the passengers of the huge plane looked down for a moment perhaps, but continued with their papers or books immediately, for this long monotonous trip was most annoying to them. It seemed unnecessary to spend six good hours in a short 3,500-mile trip like this. There was nothing to do either, not like the trans-Pacific liners, for though they spent nearly ten hours in flight they at least had club rooms and a swimming pool. There was nothing to do, nothing to see, except a slowly passing landscape ten miles below. No details could be distinguished, and the steady low throb of the engines, the whirring of the giant propellers, the muffled roar of the air, as it rushed by, combined to form a soothing lullaby of power. It was all right for pleasure seekers and vacationists, but the business man was in a hurry.

	The pilot of the machine took a last glance at the instruments, wondered vaguely why he had to be there at all, then turned, left the pilot room in charge of his assistant, and went down to talk with the chief engineer.

	His vacation began the first of Sol, and as this was the last of June, he was still rather wondering what would have happened if he had done as he had been half inclined to do—quit the trip and let the assistant take her through. It would have been very simple—just a few levers to manipulate, a few controls to set, and the instruments would have taken her up to ten or eleven miles, swung her into the great westward air current, and leveled her off at five hundred and sixty or so an hour toward 'Frisco. They would hold her on the radio beacon course better than he ever could. Even the landing would have been easy. The assistant had never landed a big plane, but if he had been shown which control to reset, the instruments would do it. If he forgot his instructions, he would merely have to leave it alone and in ten minutes it would land automatically—if an emergency pilot didn't come up by that time in answer to the automatic signal.

	He yawned and sauntered down the hall. He yawned again, wondered what made him so sleepy—he hadn't been out the night before—oh—why—worry—.

	He slumped limply to the floor and lay there breathing even more and more slowly.

	The officials of the San Francisco terminus of The Transcontinental Airways Company were worried. The great Transcontinental express had come to the field, following the beam radio signals, and now it was circling the field with a small red-and-white flag flying, the automatic signal for an emergency pilot. They were worried, and with good reason, for on this express a large shipment of negotiable securities was being sent.

	There were nearly nine hundred thousand dollars' worth of bonds. But what could attack one of those giant ships. It would take a small army to overcome the crew of seventy and the three thousand passengers!

	The great ship was landing gently now; the long series of broad rollers on its keel touching the ground evenly; its tremendous weight distributed over a great area, lest it sink into the springy, rubber-faced landing surface.

	The small field car ran over to the great plane rapidly. Already the elevator was in place beside it, and as the officials in the car drew up under the giant wing they could see the tiny figure of the emergency pilot beckoning to them. Quickly they entered the portable elevator and were carried rapidly up to the fourth level of the ship.

	What a sight met their eyes as they entered the main salon of the giant plane! All the passengers lay sleeping in their chairs, but on closer examination it became evident that they were not breathing. The ear could detect no heart-beat. The members of the crew lay at their posts, as inert as the passengers! The assistant pilot lay on the floor beside the instrument panel—he had apparently been watching the record of the flight. But there was no conscious man on board!

	"Dead! Over three thousand people! It seems impossible—how could they have done it? Gas, I suppose, drawn in through the ventilator pumps and distributed to all the compartments of the ship. But I can not conceive of any man being willing to kill three thousand people for a mere million!

	"Did you call a doctor by radio, Pilot?" The field manager was greatly depressed.

	"Yes, sir. He is on his way. There is his car now."

	"Of course they will have opened the safe—but let us see how it was done. I can only think some madman has done this—no sane man would be willing to take so many lives for so little." Wearily the men descended the stairs to the mail room in the hold.

	The door was closed, but the lock of the door was gone, apparently the magnesium-beryllium alloy had been burned away. They opened the door and entered. The room seemed in perfect order. The guard was asleep in the steel guard chamber at one side, it seemed from the doorway; the thick, bullet-proof glass made his outlines a little blurred, and the color of his face was green—but they knew there too must be that same white pallor they had seen on the faces of the passengers and crew. The delicate instruments had brought in the great ship perfectly, but it was freighted with a cargo of dead! They entered the room further, and proceeded to the safe, but it was opened as they had expected, the six-inch tungsto-iridium wall had been melted through. To the worried and depressed men this did not bring the surprise it ordinarily would have. They only glanced at the metal, still too hot to touch, and looked about the room. The bonds had been taken. But now they noticed that over the mail-clerk's desk there had been fastened a small envelope. On it was printed:

	TO THE OFFICIALS OF THE SAN FRANCISCO AIRPORT

	Inside was a short message, printed in the same sharp, black letters:

-
To the Officials of the San Francisco Airport

	This plane should land safely. If it doesn't, it is your fault, not mine, for the instruments that it carries should permit it. The passengers are NOT dead! They have been put in a temporary state of suspended animation. Any doctor can readily revive them by the injection of seven c.c. of deci-normal potassium iodide solution for every 100 pounds of weight. Do Not Use Higher Concentrations. Lower concentrations will act more slowly.

	You will find that any tendency toward leprosy or cancer will have been destroyed. It will kill any existing cancer, and cure it in about one week. I have not experimented with leprosy beyond knowing that it is cured very quickly.

	This is an outside job. Don't bother the people in the car.

	The gas used cannot be stopped by any material I know of. You can try it with any mask—but don't use the C-32L. It will react with the gas to produce a permanent suspension of animation. I would advise that you try it on an animal to convince yourselves.

	I have left stock in my new company to replace the bonds I have taken.

	Piracy Incorporated is incorporated under my own laws.

The Pirate.
-

	On the desk beneath the note was a small package which contained a number of stock certificates. They totalled $900,000, listed apparently as "Piracy Preferred," the stock of the new corporation, "Piracy, Inc.".

	"Piracy! Pirates in the air! In 2126 we have a pirate attacking our air lines. But thank God he did not kill all those people. 'Piracy Preferred.' Well, I think I would prefer the bonds myself. But if the Air Guard can't catch that fellow, I'm going to buy up his stock. From present appearances it looks to me as if it would pay big dividends! Ah, Doctor, you look worried! No wonder! But cheer up. If what this pirate says is true, we can resuscitate them, and they will be better off for the experience!"

	"I am afraid that you will never be able to bring those men back to life again, sir. I can't detect any. heart action even with the amplifier. Ordinary heart action sounds like a cataract through this instrument. I can see nothing wrong with the. blood; it has not coagulated as I expected, nor is there any pronounced hydrolysis as yet. But I am afraid I will have to write out the death warrants for all those men and women. One of the people on that ship was coming to see me. That is how I happened to be on the field. Perhaps it is better so. That poor woman was suffering from an incurable cancer."

	"In this case, Doctor, I hope and believe you are wrong. Read this note!"

-

	IT was two hours before the work of reviving the passengers could be begun. Despite all the laws of physics, their body temperature had remained constant after it reached seventy-four, showing that some form of very slow metabolism was going on. As they were one by one put into the large electric blankets, and each given the correct dose of the salt, the men waited anxiously for results—and within ten minutes of the injection the first had regained consciousness!

	The work went forward steadily and successfully. Every one of the passengers and crew was revived. And the Pirate had spoken the truth. The woman who had been suffering from cancer, was free from pain for the first time in many months. She was cured!

	The papers were issuing extras within five minutes of the time the great plane was landed, and the radio news service was broadcasting the first "break" in a particularly dead month. All this June the news had been dead, and now it looked as though the month of So! was going to begin with a bang! And now with time to think and investigate, the airport officials went over the ship with the Air Guard, using a fine-tooth comb. It was soon evident that the job had been done from the outside, as the Pirate had said it was. The emergency pilot testified that when he entered, he found a small piece of wire securing the air lock from the outside. This had certainly been put on while the ship was in flight, and that meant that whoever had done this, had landed on the great ship with a small plane, anchored it in some way, then entered the plane through the air lock at the ten-mile height. That required that he should wear a suit to protect him both from the intense cold and from the low pressure. He had probably flown across the path of the plane with his plane, leaving a trail of the gas in its way to be drawn in through the ventilator pumps. It had been washed out by the incoming good air later, for the officials had not been affected; nor had the emergency pilot been acted on when he entered.

	Now the investigation led them to the mail-room. The door had been opened by melting or burning out the lock. The heat of the combustion of the magnesium was enough for that, but the beryllium and special anti-combustion catalyst made this very difficult. But now they realized the truly amazing fact: the safe had been opened by melting it through. There was practically no oxidation of the cut itself, but the metal near by, which had been incandescent no doubt, was coated with a thin layer of tungsten oxide. The iridium content really prevented oxidation, and with a melting point of 3500 degrees centigrade it meant that the Pirate must have an entirely new torch. This would be as great a boon to the metallurgical industries as the cancer cure would be to the medical. It had been impossible to weld the valuable tungsten alloys they had prepared, and so they were useless. If they could only be worked, their ability to stand high temperatures would make them invaluable.

	A bond shipment was due the next day, and so they would be on the watch for it. It would get through safely, for men were put on board in steel tanks hermetically welded behind them, with oxygen tanks sealed within to supply them with clean air. Automatic apparatus was arranged to keep them supplied with the correct amount of oxygen without effort on their part. The waste gases were collected by alkali, a small electrically driven pump taking care that the flow was maintained. The front of the tank was equipped with a bullet-proof glass window, and by means of electrically operated controls the man inside could control a machine-gun. Thus he was perfectly protected from the Pirate's gas and able to use his gun.

	The ship was accompanied by a patrol of Air Guardsmen. Yet, several cancer cases were going with the hope of being gassed.

	It seemed that the Pirate's "patients" were due to be disappointed, though, for he certainly could not attack while the plane was under the protection of a patrol of Air Guardsmen; besides which, the men inside were protected by the steel tanks.

	When the plane reached the neighborhood of San Francisco the Air Guardsmen were disappointed, for there had been no sign of an attack on the plane. The Pirate might well retire permanently on a million, if he were alone, as the singular signature would indicate; but it seemed doubtful and it was much more probable that he would attempt another attack in any case. Well, that just meant watching all the planes from now on. That was a tremendous job for the Air Guard to handle! There was a vast network of plane lines! The leader of the patrol turned in an easy bank to descend the ten miles to earth, and his planes followed him. Then out of the corner of his eye he saw a flash of red and white on the silvery surface of the giant plane. THE PLANE WAS GIVING THE AUTOMATIC SIGNAL FOR AN EMERGENCY PILOT! That could only mean that the plane had been gassed under the very eyes of his men!

	The bonds were gone and the passengers gassed, but incredible as it was, the men aboard in the steel tanks were as thoroughly gassed as the rest! The note was brief, but as much to the point as was the absence of the bonds.

-
To the Officials of the Airport

	Restore as usual. The men in the tanks are asleep also—I said this gas would penetrate any material. It does. A mask obviously won't do any good, as the gas will permeate the skin. Don't try that C-32L mask. I warn you it will be fatal. My gas reacts to produce a poisonous substance when in contact with the chemicals used.
The Pirate.

-

	ON the thirty-ninth floor of a large New York apartment two young men were lounging about after a strenuous game of tennis. The blue curls of smoke from their pipes rose slowly, to be drawn away by the efficient ventilating system. The taller of the two seemed to be doing most of the talking. In the positions they had assumed it would have been rather difficult to be sure of which was the taller, but William Morey was a good four inches taller than Richard Arcot. Arcot had to suffer under the stigma of "runt" with Morey around—he was only six feet tall. But the chosen occupation of each was physical research, and in that Arcot could well have called Morey "runt," for Arcot had only one competitor in that field—namely, his father. In this case it had been "like father, like son." For many years Robert Arcot had been known as the greatest American physicist, and probably the world's greatest. More recently he had been known as the father of the world's greatest physicist. Arcot junior was probably one of the most brilliant men the world had ever seen, and he was aided in all his work by two men who could help him in a way that amplified his powers a thousand fold. His father and his best friend, Morey, were the complementary and balancing minds to his great intelligence. His father had learned through years of work the easiest and best ways of performing the many difficult feats of laboratory experimentation. Morey had a mind that could develop the mathematical theory of a hypothesis far more readily than Arcot could. Morey had a mind more methodical and exact than Arcot, but Arcot had a mind that could grasp the broad details of a problem and get the general method of solution developed with a speed that made it utterly impossible for his friend to even follow the steps he suggested.

	Since Arcot junior's invention of the multiple calculus, many new ramifications of the old theories had been attained, and many developments had been possible.

	But the factor that made Arcot most successful in his line of work was his ability to see practical uses for things, an ability that is unfortunately lacking in so many great physicists. Had he collected the royalties his inventions merited, he would have been a billionaire twice or thrice over. Instead he had made contracts on the basis that the laboratories he owned be kept in condition, and that he be paid a salary that should be whatever he happened to need. Since he had sold all his inventions to The Transcontinental Airways, he had been able to devote all his time to science, leaving them to manage his finances. Perhaps it was the fact that he did sell these inventions to the Transcontinental that made these lines so successful, but at any rate President Arthur Morey was duly grateful, and when his son was able to enter the laboratories he was as delighted as Arcot.

	Now these two were boon companions. They worked, played, lived and thought together.

	Just now they were talking about the Pirate. This was the seventh day of his discovery, and he had been growing steadily more menacing. It was the. great Transcontinental Airways that had suffered most repeatedly. Sometimes it was the San Francisco Flyer that went on without a pilot, sometimes the New York-St. Louis expresses that would come over the field flying the red-and-white flag of emergency. But always the people were revived with little difficulty, and each time more of the stock of "Piracy, Inc." was accumulated. The Air Guard seemed helpless. Time and again the Pirate slipped in without their knowing it. Each time he convinced them that it was an outside worker, for the door was always sealed.

	"Dick, how do you suppose he gets away with the things he does right under the eyes of those Air Guardsmen? He must have some system; he does it every time."

	"I have a very vague idea. I was going to ask you today, if your father would let us take passage on the next liner carrying any money. I understand the insurance rates have been boosted so high that they don't dare to send any cash by air any more. They have resorted to the slow land routes. I guess they pay for it, though, in the loss of interest, while the money is out of circulation. Is there any money shipment in sight?"

	"No, but I have something that is just as good, if not better, for our purpose. The other day several men came into Dad's office, to charter a plane to carry than to San Francisco, and Dad naturally wondered why it was they had been referred to the president of the company. It seemed to him to be a job for a clerk. It seems the difficulty was that these men wanted to hire the ship so they could be robbed! A large group of medical men and cancer victims were going for the 'treatments.' Each one of the twenty-five hundred going was to bring along one hundred dollars. That meant a total of a quarter of a million dollars, which is to be left on the table. They hoped the Pirate would gas them and thus cure them! Dad could not officially do this, but told them that if there were too many people for the San Francisco express, two sections would be necessary. So I believe that they are going on that second section. Only one hundred dollars! It seems a very cheap cure for cancer at that!

	"Another thing: Dad asked me to tell you that he would appreciate your help in stopping this ultra-modern pirate. So if you go down and see him in the morning, you will doubtless be able to make the necessary arrangements."

	"I will do so gladly. I wonder, though, if you know more about this than I do. Did they try that C-32L mask on any animal?"

	"The Pirate was telling the truth. They tried it on a dog and he went to sleep forever. But do you have any idea how that gas does all it does?"

	"I don't know what that gas is, but I can tell you some things that you may not know. Did you know, for instance, that carbon monoxide will seep through a solid plate of red-hot steel? That has been known for some three hundred years now, and I have to hand it to this Pirate for making use of it. Even in the war of 2075 they didn't think of it! He has just found some gas that has these sleep-producing properties in very low concentrations, and at the same time is able to penetrate to an even greater extent than carbon monoxide. It is just an amplification of known properties."

	"I was wondering how he stores that stuff. It reminds me of the old farmer and his smart son who had almost discovered the Universal Solvent.

	" 'Well son,' said the old farmer, 'I suppose it'll be a durned good thing ta have, but what you going to keep it in?' Similarly, if this gas leaks through everything, what are you going to keep it in? I wonder if he doesn't make it as fast as he uses it, by allowing the two constituents to react? It might well be simple enough to store them separately, and the airstream blowing past him would carry the gas behind him, so permitting him to lay a stream of it in front of the big plane. Is that about it?"

	"That was about what I had figured. One of the things I want to do when I go with that Invalid Special tomorrow is to get some samples for analyses."

	"Whew, that's a pretty big order, isn't it, Dick? How are you going to handle it, or even get it into your apparatus?"

	"Easily enough as far as getting the sample goes. I have already had some sample bottles made. I have one of them in the lab—excuse me a moment." Arcot left the room, to return a few minutes later with a large aluminum bottle. ''This bottle has been pumped out to a very good vacuum. I then swept it out with helium gas. Then it was pumped out again. I hope to take this into some gas-filled region, where the gas will be able to leak in. but the air won't. When it comes to going out again, the gas will have to fight air pressure, and will probably stay in. I cannot hope to find its molecular weight by any normal means. Probably the Pirate doesn't know it—but I will be able to get a known weight of the sample, the weight being the difference between the weight before and after the gas attack. That is why I used helium in sweeping the bottle out. It will not be in the compound, that is certain. It is absolutely impossible for it to combine. It will weigh very little and won't offset my readings, and won't react with the gas itself. I can't hope to learn much that will be very useful, for the organic tables are so blamed complex, that a mere empirical formula won't mean a thing. C2H6O is the formula for ethyl alcohol—or it's the formula for methyl ether. It may be a single, double or triple bonded compound—but I can't tell. I will be able to get the empirical formula, though, for any organic compound is apt to decompose easily, and I will just heat my cylinder in a furnace till the gas is broken down, then it will be easy to analyze the residue."

	"I am not a chemist! You know that, but I know that the amount of gas you will get in that bottle will not weigh as much as a gram. Now how do you intend to analyze that?"

	"They have been making analysis runs on such small amounts of compounds that they had to use powerful lenses in watching the reactions! Two hundred years ago an Austrian developed micro-analysis. Remember that in organic chemistry it is frequently necessary to make an analysis of some substance that has been derived only after many long months of hard work. Frequently the entire sample will weigh not more than a hundredth of a gram. The chemist must run at least three or four analyses on that. He had to work with pinhead amounts! It will be no great amount of labor for Jackson to work it out. It will probably irritate his chemist's soul to make an analysis and have to stop at the empirical formula, but I don't see how he can do any more!"

	"Beautiful scheme! I hope you can find out something about it!"

-

	THE next morning saw Arcot in President Morey's private office, having a long conference with him. At the end of it, he left the office, ascended to the roof, and climbed into his small helicopter, rose to the local traffic level, and waiting his chance, broke into the traffic bound for the great airfields over in the Jersey district. A few minutes later he landed on the roof of the Transcontinental Airways shops, entered them, and went to the office of the Designing Engineer, John Fuller, an old schoolmate. They had been able to help each other before, for Fuller had not paid as much attention to theoretical physics as he might have, and though he was probably one of the outstanding aeronautical designers, he often consulted Arcot on the few theoretical details that he needed. Probably it was Arcot who derived the greatest benefit from this association, for the ability of. the designer had many times brought his theoretical successes to practical commercial production. Now, however, he was consulting Fuller, because the plane he was to take that afternoon for San Francisco was to be slightly changed for him.

	He stayed in Fuller's office for the better part of an hour, then returned to the roof and thence to his own roof, where Morey junior was waiting for him.

	"Hello Dick! I heard from Dad that you were going this afternoon, and came over here. I got your note and I have the things fixed up here. The plane leaves at one, and it is ten-thirty now. Let's eat lunch or its equivalent, and then start. Dad asked me to see how good that engineer on this plane is at explaining the stuff. You know the engineers are supposed to be able to tell those visitors, who have passes, all about it. I am going to try to get there early, and we have passes—John Smith is yours and mine is Charles Black. Let's see—we'll be English."

	It was half-past eleven when they reached the flying field. They went directly to the private office which had been assigned to them aboard. It was right next to the mail-room, and through the wall between the two a small hole had been cut. Directly beneath this hole was a table, on which the two men now set up a small moving-picture camera they had brought with them.

	"How many of the gas sample bottles did you bring, Bill?" asked Arcot.

	"Jackson had only four ready, so I brought those. I think that will be enough from what he said. Have we got that camera in place right now?"

	"Everything's O. K. I believe. Let's see your engineer."

	The chief engineer was lounging about in a large chair in his cabin. The walls of the little metal room were lined with meters and rheostat controls. He wished they would get started. He was a little disgruntled at present, his mates had been kidding him at the lunch room—he was now "chief engineer of the Invalid's Flying Wheel Chair"! He was rather glad to be gassed on these trips. It made the trip even shorter. He glanced up at the long rows of meters and smiled. What did they spend all that money for? No one ever paid any attention to those things except once in every month, when the planes were run by the shop specialists; then they checked things up, but the automatic devices managed the whole thing anyway. His principal duly lay in keeping his men at the engines, and inspecting the apparatus occasionally. But if anything went wrong—a plane had had trouble three years ago and descended to the six-mile level before the engineer had been able to get the machines working correctly again. No hum—hullo—some visitors. Well, here was a little diversion while he waited for the starting signal. English they were.

	"President Morey sent us to see you. We are trying to collect some material on American lines, and we are touring your country. We would greatly appreciate it if you would just tell us the story from the beginning." Hmmm, friends of the president himself—well—

	"I'll be glad to help you all I can, Mr. Smith. What would you like to see first?"

	"Well, I think we'd best see the engines first, if possible."

	"All right, sir. I guess we can go down to the main engine room in the nose of the ship. This is the Chief Engineer's control room. That board there represents the main engine. It covers most of that side of the room; there are most of the controlling relays for starting and running it. The engines are really run by the control mechanisms. You know those were begun over two hundred years ago, and through that time they have passed through all the stages. First they were indicators, watched by men who then acted on their information. Then about that time relays were developed to control the action of the big planes that developed. The first of these was the DO-X, the one they have in the National Teutonic Museum. They got so big one man couldn't handle them, and then the relays took over the job. By that time the instruments had become more accurate, and they just hooked the relays directly to the instruments.

	Now we have these ships. Each airline has a radio beam station at each end, and several scattered along the way. These direct the instruments which control the direction of the ship. The height is controlled by the radio reflection altimeter. This gives us ground height, the altitude from the ground itself, not from sea level—it makes it possible for these big planes to land themselves automatically. The plane will no doubt be gassed, as you probably know, and it will then continue its way controlled automatically. Freight lines frequently operate that way during rush periods. No pilot goes on them, and no crew. There is a landing beacon that projects a radio wave from the exact center of the field. The plane heads for this, then lands gently. A fall of a foot or so is easily taken care of by the shock absorbers.

	"You noticed the roller landing gear? That has not been adopted widely abroad as yet, but it makes for easier landings. The weight of the ship is distributed over much greater area, and it does away with a tremendous amount of head resistance. These rollers have been nearly completely countersunk, and wheels cannot be.

	"Here is the main engine room. That engine there develops about 25,000 horsepower. There are two smaller engines, one on each side, out in the wings. These develop only about 15,000 apiece. These are the usual American type engine, the Arcot coal engine, patterned after the old Diesel engine. They were developed by Arcot senior about fifty years ago, and have been little improved since, though young Arcot has added a new type of vibration damper. They burn powdered coal, by the compression ignition method. Coal is powdered to an exceedingly fine dust and blown into the cylinders, where the up-stroke compresses the air to about 1,500 pounds to the square inch. The fuel is burned with about thirty-nine percent efficiency, as compared to the old di-phenyl-oxide vapor turbines which developed about ten per cent at best. The fuel is solid, and easily handled, and further, there is no fire risk.

	"The engines have sixteen cylinders of rather small size, for it was found that small cylinders with great pressures and several in number gave higher efficiency and less vibration than fewer large ones. The big mechanism up there reduces the speed of the engine shaft to a speed that can be used on the props. The main prop is forty feet sweep, the two others are each thirty feet.

	"When the oil supplies gave out in 2060-80, the engineers were mighty hard pressed. Fuel they had in the form of coal. For many years the problem had been staring them in the face, and they had really solved it. Of course there still remained the oil shales, but they could not be worked economically because of the cost of extracting the oil. It was cheaper to import the lubricants they had to have. These they tried to eke out with copious amounts of graphite, and re-refining. Then about 2070 some genius, many claim the honor, got the very sensible idea that it was time they started raising their own oil. Now, as we fly over western Kansas, you will see vast fields of green plants. From there, clear across the country, the green will continue. They are the gigantic plantations where our oil and most of our fuel is grown. The cornstalks are used as fuel and a dozen other things by fermentation by particular bacterial ferments. Alcohol is the usual product, but many others can be obtained. Further west, the staple crop is castor oil beans. That is the source of our lubricating oil. Some man dug the secret out of some century and a half-old book, for in the days of the development of the automobile it was found that the petroleum was not good enough at that time, to use in the expensive racers, and they used castor oil, which did not trouble them by dissolving the gasoline. That big tank up there is the main supply. It is loaded with synthetic graphite also, for even that needs a little thinning to go round. Our fields aren't big enough yet. The castor oil bean plant is one of the necessities of this country. It supplies our oil, and it helps supply our alcohol. Of course, we do use hydrogenated coal to a slight extent still, but the main fuel is alcohol. How do you manage in England? You do not have enough area for castor oil production, and not enough coal left."

-

	ARCOT and Morey had not been prepared for this, but Morey happened to be up on those facts at present from a recent trip to European cities.

	"Why, we are using methyl alcohol as our fuel. Your ethyl alcohol used commercially can be prepared by fermentation with your great area, but we have been forced rather to extremes. As you know, we are now synthesizing the staple items of our food directly. Our coal too is nearly exhausted and we are beginning to wonder if the old idea that Englishmen had was so good. You know we used to sell our coal by the millions of tons to ships every year. Now we need it badly. We have been forced to use our great deposits of limestone and other carbonates as our source of carbon. The usual practice is to electrolyze sea water for the chlorine and the sodium as well as the hydrogen. The H and the CI are burned together to give the acid. This is used to treat limestone to produce the CO2 needed in industry, the heat of the reaction producing CO2 by the direct decomposition of the limestone. The calcium chloride is now a very important by-product, while the CO2 thus obtained is used to produce the necessary foods and fuels. The usual system is to treat it with hydrogen gas and produce methyl alcohol. This is then synthesized up to sugars and other simple foods. The power we use comes directly from the sea by the process of using the difference in temperature of the sea water at great depths and on the surface. The power stations have been built all along the coast now, and great transmission lines reach inland to supply the cities with power.

	"There are no chimneys in England today. The newest process looks as if it had great promise; it is simpler than the old methods, and uses far less energy. They pass air through a liquid under great pressure, and in this way absorb the CO2 content of the air. The thing becomes most interesting to look on in the whole! The energy comes from the sun. It is used to stabilize carbo-hydrogen compounds, the carbon coming from the air as CO2 and the hydrogen from water. The resultant foods are used by the developers of the machine, and we have at last gotten back to the model the plant offered millions of years ago! This time, with the sun as our source of energy, we don't have to worry about running out of fuel!"

	"In this country, Mr. Black, we have been forced to use our coal very sparingly for all but absolutely essential industries. We need it for metallurgical processes. What do you use?"

	"That was one of our big problems. We now find it necessary to get most of our metals electrolytically, the power being generated, as I state, from the sea. It is cheap, and our costs are not so much greater than yours, and our supply of power will last forever. The only trouble is that the metals are showing signs of exhaustion. As you know, we now have to import practically all our metals except iron, but even that shows signs of giving out. France is in a like condition, her coal and iron are nearly gone, and even Germany is feeling the stress pretty badly. Russia and Siberia, with their vast area, have little to worry about. They are still producing oil in plentiful amounts. Their platinum alone seems to be exhausted. But the day will come! I wonder what we will do when there is no more high-grade iron ore?"

	"Let's not think about that. It probably won't come in our day."

	"Probably not; still, there is the question."

	While the men had been talking, the great landing field had been gradually dotted with people moving over toward the great ship. It would start now in about twenty minutes. The engineer suggested that they go upstairs and watch things from the pilot's room.

	"See the big tubes on top of the roof of the station there? Those are the radio beacon generator tubes. They, and others like them in San Francisco, will be directing the ship as she flies along her route, ten miles up. As in the European lines, we fly at about ten miles, thus avoiding any danger of mountains, cutting down air resistance, and increasing the safety factor of landing. With the main engine alone going, we can reach San Francisco from New York once we get altitude. With none of the engines going we can always glide to one of the big cities, for a safe landing. So great is the area of gliding range that there is no place on all earth where we would not be within reach of a safe landing. There is no danger of the engines failing anyway, so we really don't have to worry. Should they have a breakdown after the pilot and the crew have been gassed, the instruments will cut them out automatically lest they wreck the ship, and then it will make a safe automatic landing at any nearby city, by picking up the strongest of the local guide beacons. Usually, if there is any emergency, the pilot sits back and just lets the machines handle it. They never make a mistake, as long as they are working. When they stop working, the pilot takes charge. But they have never been known to stop working. That large case over there conceals a big battery of constantly charged storage cells that operate the instruments. We do not take any chances on power failure.

	"See—they are getting ready to take-off. They will close the air doors soon. I must go back to my office, but you can stay here and talk to the pilot—he won't have anything to do anyway!"

	"No, I won't, Chief, but that will be because the pilot's had sense enough to invent machines to make life easy!" returned the pilot. "But I will be glad to help you gentlemen if I can. There—hear that whir—now it has almost gone. They started the ventilator machinery. That will draw air in from outside, and pump it up to the necessary pressure for breathing in the ship, no matter what the external pressure is. There is a much bigger pump attached similarly to each of the engines to supply it with the necessary oxygen. You would think that this would take a lot of the power from the engines, but any loss in pumping the air in is made up by the lower back pressure on the exhaust. Now the engines are starting—feel the momentary vibration—then it goes as they get under way. The props haven't been thrown in gear as yet. The air-tight door is closed now; the portable elevator is backing off, going back toward the field house. I don't think it is particularly portable! But, then, one wouldn't say a thing like this machine looked very capable of flight while it is on the ground, yet in the low resistance air, ten miles up, we will make over six hundred at times. Well, it's one now, and the starting signal is due. I am afraid I must be excused now."

	Arcot and Morey returned to their room, convinced that both pilot and engineer were intelligent and courteous.

	"Well, now we have a nice long wait till we get to San Francisco and back, Dick, but you will have something to tell then!"

	"I hope so, Bill, and I hope that as soon as we get there, we can get ready to take the midnight plane from San Francisco, which will get us in at nine o'clock tomorrow morning, New York time. I wish you would go right to your father's office and ask him over to our place for supper, and see if Fuller can come too. I think we will be able to use that molecular controller on this job; it is almost finished, and with it we will need a good designing engineer. Then our little movie show will no doubt be of interest!"

-

	THERE was a low rumble that quickly mounted to a staccato roar as the great propellers began whirling and the engines took up the load. The ground began to flash behind them; the giant plane was waddling awkwardly across the surface, like a great duck, then suddenly, as flying speed was reached, there was a slight start, the roaring bark of the engine took on a deeper tone, the rocking stopped and the ground was dropping away. Like some mighty wild duck, the plane was in the air, a graceful, sentient thing, wheeling in a great circle as it headed back for San Francisco, for the wind had been from the cast when the ship took off. Now the plane was climbing steadily in a long bank; up, up, up she went, and gradually the terrific roar of the engine died to a low throbbing hum as the low pressure of the air silenced the noise, a sound proof vacuum was around them. Below them the giant city was contracting as the great ship rode higher. The tiny private helicops were darting about below them like streams of nigh invisible individuals, creeping black lines among buildings of the cities. The towering buildings shone in the noon sun in riotous hues as the colored tile facing reflected the brilliant sunlight with glowing warmth of color.

	It was a city of indescribable beauty now. It was one of the things that made this trip so worth-while.

	Now the shining city was dropping behind them, and only the soft green of the Jersey hills, and the deep purple-black of the sky above surrounded them. The sun was blazing high in the nigh-black heavens, and the rarefied air gave such slight diffusion effect, that the corona was readily visible with the aid of a smoked glass. Around the sun, long banners in space, the Zodiacal light gleamed dimly. Here and there some of the brighter stars gleamed in the dark sky.

	Below them the landscape was swinging slowly by. Even to these men who had made the trip dozens of times, the sight was one to inspire, and hold one's attention, it was such a thing as had never been visible before the development of these super-planes. Whole flying observatories had been made that had taken photographs at heights of fifteen miles, where the air was so rarefied that the plane had to travel close to eight hundred miles an hour to stay up. Giant power was needed to maintain this speed, and only on rare occasions were the machines taken so high, but the flexibility allowed far better observation of solar eclipses than had ever been possible, for but once in a century would an eclipse occur in the region of a large observatory.

	Already ahead of them Arcot and Morey could see the great splotch of color that was Chicago, the mightiest city of the Earth. Situated as it was in tire heart of the North American continent, with great water and ground landing facilities and broad plains about it, it made a perfect air-port, and the sea no longer meant much, for it was now only a source of power, recreation and food. Ships were no longer needed. Planes were faster, and the air resistance being so much less, it was more economical also. With its already great start toward ascendancy, Chicago had rapidly forged ahead, as the air lines developed with the great super-planes. The European planes docked here, and it was the starting point of the South American lines. But now, as they swung high above it, the glistening walls of soft-colored tiles made it a great mass of changing, flashing color beneath them. As they passed they could see a great air "liner, twice the size of their plane, taking off for Japan, its five giant propellers visible only as flashing blurs as it climbed up toward them. Then it was out of sight.

	It was over the green plains of Nebraska that the Pirate worked, so there the men became more and more alert, waiting for the first sign of abnormal sleepiness. The tenseness made them yawn, and each immediately wanted to start the camera lest they miss the raider. They soon realized, however, that it was only their nervousness that made them yawn so. They sat quietly, not talking, listening intently for some new note, but knowing all the while that any sound the Pirate might make would be more than drowned out in the whirring roar of the air sweeping past the giant airfoils of the plane.

	It was Arcot who first began to feel sleepy, and soon he decided that it was not imagination. He glanced sleepily toward Bill, who was already lying down. He found it a tremendous effort of the will to make himself reach up and close the switch that started the little camera whirring almost noiselessly. It seemed he never pulled his arm back—he just—lay there—and—

	A white uniformed man was bending over him as he opened his eyes. To one side of him he saw Morey smiling down at him.

	"You're a fine guard, Arcot. I thought you were going to stay awake and watch them!"

	"Oh, no, I left a much more efficient watchman! It didn't go to sleep—I am willing to bet!"

	"No, it may not have gone to sleep, but the doctor here tells me it has gone somewhere else. It wasn't found in our room when we woke up. I think the pirate found it and confiscated it. All our luggage, including the gas sample bottles is gone."

	"That is all right. I arranged for that. The ship was brought down by an emergency pilot and Fuller had him fixed for me. He took care of the luggage so that no member of the pirate's gang could steal it. There might have been some of them in the ground crew. They will be turned over to us as soon as we see the emergency man. I don't have to lie here any longer, do I, doctor?"

	"No, Dr. Arcot, you're all right now. I would suggest that for the next hour or so you take it easy to let your heart get used to beating again. It stopped for some two hours, you know. It is hard to change a habit of some twenty-five or six years, but once changed, it is hard to change back. You will be all right, though."

	Five men were sitting about the table, discussing the results of the last raid, in particular as related to Arcot and Morey. Fuller, and President Morey, as well as Dr. Arcot, senior, and the two young men, were there. They had consistently refused to tell what their trip had revealed, saying that pictures would speak better than they could. So now the men adjourned to the library where a small motion picture projector had been set up. As they seated themselves in the darkened room, Arcot set up the small screen, then returned to the projector and stalled it. At once they were looking at the three dimensional image of the mail-room aboard the air liner.

	"I have cut out a lot of useless film, and confined the picture to essentials. We will now watch the pirate at work."

	Even as he spoke they saw the door of the mail-room open a bit, and then, to their intense surprise, it remained open for a few seconds, then closed. It went through all the motions of opening to admit someone, yet no one entered!"

	"Your demonstration doesn't seem to show much yet, son. In fact, it shows much less than I had expected," said the senior Arcot. "But that door seems to open easily. I thought they locked them!"

	"They did, but the Pirate just burned holes in it, so to save expense, they don't anymore."

-

	NOW the scene seemed to swing a bit as the plane hit an unusually bad air bump, and through the window they caught a glimpse of one of the circling Air Guardsmen. There suddenly appeared in the air a bit of flame. It hung in the air above the safe for an instant; described a strangely complicated set of curves; then, as it hung for an instant in mid-air, it became a great flare. In an instant it narrowed down to a little point of brilliant red flame. This described a complex series of curves and touched the safe at the top. In an inconceivably short time the eight-inch thickness of tungsto-iridium alloy was glowing incandescent and running around molten; a large flare of the red flame sprang out to surround the point of flame, and this blew the molten metal to one side, a shower of brilliant sparks. It was cutting the metal rapidly now, not burning it, but blowing it to one side, perfectly fluid.

	Soon the torch had cut a large circular piece of metal nearly free, and it would soon drop into the safe. Now the torch left the safe, again retracting itself in that uncanny manner, no force seeming either to supply it with fuel or to support it thus, yet it burned steadily, and worked rapidly and efficiently. No, in mid-air, it hung for a second.

	"I'm going to work the projector for a few moments by hand so that you may see this next bit of film." Arcot moved a small switch and the machine blinked, giving a strange appearance to the seemingly solid images that were thrown on the screen.

	The pictures seemed to show the flame slowly descending till it touched the metal again. Again the metal glowed, then, as suddenly as the extinguishing of a light, the safe was gone! It had disappeared into thin air! Only the incandescence of the metal and the flame were visible.

	"It seems the pirate has solved the secret of invisibility. No wonder the Air Guardsmen couldn't find him!" exclaimed Arcot, senior.

	The projector had been stopped exactly on the first frame, showing the invisibility of the safe. Then Arcot backed it up.

	"I think you are right, dad," he said, "but notice this next frame."

	Now there appeared a picture of the room again, the window beyond, the mail clerk asleep at his desk, everything as before, except that in the place of the safe, there was a shadowy, half visible safe, the metal glowing brightly, and beside it there was visible a shadowy man, holding the safe with a shadowy bar of some sort. And through both of them the frame of the window was perfectly visible, and, ironically, an Air Guardsman.

	"It seems that for an instant his invisibility failed here. Probably it was the contact with the safe that caused it. What do you think, dad?" asked Arcot, junior.

	"It does seem reasonable. I can't see off-hand how his invisibility is even theoretically possible. Have you any ideas?"

	"Well, dad, I have, but I want to wait till tomorrow night to demonstrate them. Let's adjourn this meeting, if you can all come tomorrow."

	The next evening, however, it seemed that it was Arcot himself who could not be there. He had asked Morey, junior, to tell them he would be there later, when he had finished in the lab.

	Dinner was over now, and the men were waiting rather impatiently for Arcot to come. They heard some noise in the corridor, and looked up, but no one came.

	"Morey," asked Fuller, "what did you learn about that gas the pirate was using? I remember Arcot said he would have some samples to analyze."

	"As to the gas, Dick found out but little more than we had already known. 
It is a typical organic compound, one of the metal radical type, and contains one atom of thorium. This is a bit radioactive, as you know, and Dick thinks that this may account in part for its ability to suspend animation. Thorium has a valence of four, as have many of the semi-organic metal radicals. It is thus able to replace carbon in some structures. However, since it was impossible to determine the molecular weight, he could not say what the gas was, save that the empirical formula was C62Th H30O27N5. You can see it is a very complex molecule. It broke down at a temperature of only 89° centigrade. The gases left consisted largely of methane, nitrogen, and methyl ether. Dick is still in the dark as to what the gas is. Look over there!"

	The men turned with one accord toward the opposite end of the room, looked, and seeing nothing particularly unusual, glanced back rather puzzled. What they then saw, or better, failed to see, puzzled them still more. There was no doubt Morey could not be seen.

	"Why—why where—ohhhh! Quick work, Dick!" The senior Arcot was laughing heartily, and as the astonished and curious pair looked toward him, he stopped and called out, "Come on, Dick! We want to see you now. And tell us how it is done! I rather think Mr. Morey here—I mean the visible one—is still a bit puzzled." There was a short laugh from the air—certainly there could be nothing else there—then a low but distinct click, and both Morey and Arcot were miraculously present, coming instantaneously from nowhere, if one's senses could be relied on. On Arcot's back there was strapped a large and rather hastily wired mechanism—one long wire running from it and out into the laboratory. He was carrying a second piece of apparatus, similarly wired. Morey was touching a short metal bar that Arcot held extended in his hand, using a table knife as a connector, lest they get radio frequency burns on making contact.

	"I have been very busy getting the last connection of this portable apparatus rigged up. I have the thing in working order, as you see—or rather, didn't see. This other outfit here is the thing that is more important to us. It is a bit heavy, so if you will clear a space, I will set it down. Look out for my power supply there—that wire is carrying a rather dangerously high E.M.F. I had to connect with the lab power supply to do this, as I had no time to rig up the beautiful little mechanism the pirate must have.

	"I have duplicated his experiment. He has simply made use of a principle known for some time, but as there was no need for it, they haven't used it. It was found back in the early days of radio, as early as the first quarter of the twentieth century, that very short wavelengths effected peculiar changes in metals. It was shown that the plates of tubes working on very short waves became nearly transparent. The waves were so short, however, that they were economically useless. They would not travel in usable paths, so they were never developed. Furthermore, the apparatus developed could not be made to handle them. In the last war they tried to apply the idea for making airplanes invisible, but they could not get their tubes to handle the power needed, so they had to drop it. However, with the tube I recently got out on the market, it is possible to get down there. I think our friend the pirate has developed this thing to a point where he could use it. You can see that invisibility, while interesting, and a good thing for a stage and vaudeville, is not very much of a commercial need. No one wants to be invisible in any honest occupation. Invisibility is a tremendous weapon in war, so the pirate just started a little private war, the only way he could make any money on his invention. No one wants it. People can't use an invisible plane—they would run too much risk of being crashed. If two of the blamed things were in the neighborhood, it could never be known when one might run into the other.

	"His gas, too, made the thing attractive. He had probably discovered that before."

-

	"THE whole thing looks to me to be the work of a madman. He is not violently insane; probably just has one particular obsession. His scientific bump certainly shows no sign of weakness. He might even be some new type of kleptomaniac. He steals things, and he has already stolen far more than any man could ever have any need of, and he leaves in its place a 'stock' certificate in His own company. He is not violent, for hasn't he carefully warned the men not to use the C-32L mask? 

	"And his careful instructions as to how to revive the people! He is insane in one branch only. But he has developed this machine for invisibility, and naturally he can fly in and out of the air guard, and they will never know he's there, provided their microphonic detectors don't locate him. But they have a mighty poor chance. I believe that he uses some form of glider. He cannot use an internal combustion engine, for the light of the explosions in the cylinders would be as visible as though the cylinders were made of clear fused quartz. He cannot have an electric motor, for the storage of his energy would be a weighty matter—the cells would necessarily weigh too much. Furthermore, if he were using any sort of prop, the noise of the air around it would give him away. If he used a glider, the noise of the great ship so near would be more than enough to kill the slight sounds. The glider could hang above the ship, then dive down upon it as it passed beneath. He has a very simple system of anchoring the thing, as I discovered to my sorrow. He has a powerful electro-magnet and just turns that on when he lands. The landing deck of the big plane was right above our office aboard, and I found my watch was doing all sorts of antics today. It lost an hour this morning, and this afternoon it gained two. I found out it was very highly magnetized—I could pick up needles with the balance wheel. I demagnetized it; now it runs all right. I noticed you do the same thing to yours later, Bill."

	"I had to. It took me twenty-five minutes to walk two blocks, according to my watch. The next two blocks I did in a minute and forty-five seconds."

	"But to get back, he anchors his ship, then, leaving it invisible, he goes to the air lock, and enters. He wears a high altitude suit, and on his back he has a portable invisibility set and the fuel for his torch. The gas has already put everyone to sleep, so he goes into the ship, still invisible, and melts open the safe.

	"His power supply for the invisibility machine seems to be somewhat of a problem, but I think I would use a cylinder of liquid air, and have a small air turbine to run a high voltage generator. He probably uses the same system on a larger scale to run his big machine on the ship. He can't use an engine for that either.

	"That torch of his is interesting, too. We have had atomic hydrogen welding for some time, and atomic hydrogen releases some 100,000 calories per mole of molecular hydrogen, two grams of gas give one hundred thousand calories. Oxygen has not been prepared in any commercial quantity in the atomic state. From watching that man's torch, from the color of the flame and other indications, I gather that he uses a flame of atomic oxygen-atomic hydrogen for melting, and surrounds it with a preheating jacket of atomic hydrogen. Since oxygen has two valences instead of one, its heat of formation is greater. The center flame probably develops a temperature of some 4000° centigrade, and will naturally make that tungsten alloy run like water. But there has never been any commercial way of storing atomic hydrogen; it has always required a big electrical power supply, and expensive apparatus. Since this fellow was able to use it as a portable welding and cutting tool he has a means of storing it. I rather believe he dissolves it in some substance. Remember the difficulties they had in storing acetylene? They could not store it in the liquid state as it would often explode. They finally solved the problem by dissolving it in acetone. I think that the pirate has found some liquid that will store his atomic hydrogen under slight pressure. That is the only way he could produce the results he has. Now, as to this machine here.

	"It is, as I said, a machine which impresses very high frequencies on the body it is connected with. This puts the molecules in vibration at a frequency approaching that of light, and when the light impinges upon it, it can pass through readily. You know that metals transmit light for short distances, but in order that the light pass, the molecules of metal must be set in harmonic vibration at a rate approaching the frequency of light. If we can impress such a vibration on a piece of matter it will then transmit light very freely. If we impress this vibration on the matter, say the body, electrically, we get the same effect, and the body becomes perfectly transparent. Now, since it is the vibration of the molecules that makes the light pass through the material, it must be stopped if we wish to see the machine. Obviously it is much easier to detect me here among solid surroundings, than in the plane high in the sky. What chance has one to detect a machine that is perfectly transparent when there is nothing but perfectly transparent air around it? It is a curious property of this vibrational system of invisibility that the index of refraction is made very low. It is not the same as that of air, but the difference is so slight that it is practically within the limits of observation error; so small is the difference that there is no 'rainbow' effect. The difference of temperature of the air would give equal effect.

	"Now, since this vibration is induced by radio impulse, is it not possible to impress another, opposing radio impulse, that will overcome this tendency and bring the invisible object into the field of the visible once more? It is; and this machine on the table is designed to do exactly that. It is practically a beam radio set, projecting a beam of wavelength .09 meter, a wavelength that alone would tend to produce invisibility, but in this case it will make me visible. I am going to stand right here, and Bill can operate that set."

	Arcot strode to the middle of the room, and then Morey turned the reflector of the beam set on him. There was a low snap as Arcot turned on his set, then he was gone, as suddenly as the coming of darkness when a lamp is extinguished. He was there one moment, then they were staring at the chair behind him, knowing that the man was standing between them and it, knowing that they were looking through his body. It gave one a strange feeling, an uncomfortable tingling along the spine. Then the voice—it seemed to come from the air, or some disembodied ghost as the invisible man called to Morey.

	"All right, Bill, turn her on slowly."

-

	THERE was another snap as the switch of the disrupter beam was turned on. At once there was a noticeable fogginess in the air where Arcot had been. As more and more power was turned into the machine, they saw the man materialize out of thin air. First he was a mere shadowy outline that was never fully above the level of conscious vision. Then slowly the outlines of the objects behind became dimmer and dimmer, as the body of the man was slowly darkened, till at last there was only a wavering aura about him. With a snap Morey shut off his machine and Arcot was gone again. A second snap and he was solid before them. He had shut off his apparatus loo.

	"You can see now how we intend to locate our invisible pirate. Of course we will depend on directional radio disturbance locating devices to determine the direction for the invisibility disrupter ray. But you are probably marvelling at the greatness of the genius who can design and construct this apparatus all in one day. I will explain the miracle—I have been working on short wave phenomenon for some time. In fact, I had actually made an invisibility machine, as Morey will testify, but I realized that it had no commercial benefits, so I did not experiment with it beyond the laboratory stunt stage. I am still working on a somewhat different piece of apparatus that I believe we will find very relevant to this business. I will ask you to adjourn after tonight's meeting for another twenty-four hours till I can finish the apparatus I am working on. It is very important that you be here, Fuller. I am going to need you in the work to follow. It will be another problem in design if this works out, as I hope it will."

	"I'll certainly make every effort to be here, Arcot," Fuller assured him. "I can promise you a tough problem as well as an interesting one. If the thing works, as I expect it to, you will have a job that will certainly be a feather for your cap. Also it will be a change."

	"Well, with that inducement, spoken by you, I will certainly be here. But I think that pirate could give us some hints on design. How does he get his glider ten miles up? They have done some gliding already. The distance record took someone across the Atlantic in 2009, didn't it? I know they have about stopped, but it does seem that ten miles straight up is a bit too steep for a glider. There are no vertical air currents at that height."

	"I meant to say that his machine is not a true glider, but a semi-glider. He probably goes up ten miles or more with the aid of a small engine, one so small it takes him all morning to get there probably. It is very seldom anyone goes that high. Of course, there are some who are trying the ceiling of their new machines, but they are mighty few—it is too long drawn out a procedure. It wouldn't pay for the big Transcontinental planes to go that high, just the sheer power and work done getting there would be prohibitive if they couldn't use it all on the last part of the flight by gliding. You know that better than I do. And it would be easy for a plane to pass through the lower traffic lanes, then, being invisible, mount high and wait for the air liner. He can't use a very large engine, for it would drag him down, but a hundred horsepower or so would weigh only about 50 pounds if one of the new tungsto-iridium blade turbine engines is used. I think we can draw a pretty good picture of his plane from scientific logic. It probably has a tremendous wingspread and a very high angle of incidence to make, it possible to glide at that height, and the engine and prop will be almost laughably small."

	The next evening the meeting was resumed, and there was considerable questioning as to the nature of the discovery that Arcot was going to announce, for even his father did not know. The two men worked in separate laboratories, except when either had a particularly difficult problem that might be solved by the other. All knew that the new development lay in the field of short wave research of some sort, but they could not find out in what way it concerned the problem in hand.

	At last the meal was over, and Arcot was ready to demonstrate.

	"Dad, I believe that you have been trying to develop a successful solar engine. One that could be placed in the wings of a plane to generate power from the light falling on that surface. In all solar engines, what is the greatest problem to be solved?"

	"Well, the more I investigate the thing, the more I wonder which is the greatest. There are a surprising number of annoying problems to be met. I should say, though, that the one big trouble with all solar engines, eliminating the obvious restriction that they decidedly aren't dependable for night work, is the difficulty of getting an area to absorb the energy. If I could get enough area, I could use a very low efficiency and still have cheap power, for the power is absolutely free. The area problem is the greatest difficulty, no doubt."

	"Well, I think you have a fairly good area to use, if you can only harness the energy it absorbs. I have really developed a very efficient solar engine. The engine itself requires no absorbing area, as I want to use it; it takes advantage of the fact that the earth is absorbing quintillions of horse-power. I have merely tapped the power that the earth has already absorbed for me. Come here."

	He led the way down the corridor to his laboratory, and switched on the lights. On the main laboratory bench was set up a complicated apparatus of many tubes and heavy bus bar connecters. From the final tube two thin wires ran to a long tubular coil. To the left of this coil was a large relay switch, and a rheostat control.

	"Turn on the relay, dad, then slowly rotate the controller to the left. And remember that it is rather powerful. I know this doesn't look like a solar engine, and nine o'clock at night seems a peculiar hour to demonstrate such a thing, but I will guarantee you results—and probably more than you expect."

	Dr. Arcot stepped up to the controls and closed the switch. The lights dimmed a bit, but immediately brightened again, and from the other end of the room came a low, steady hum as the big transformer took up the load.

	"Well, from the sound of that ten K.W. transformer there, if this engine is very efficient we ought to get a terrific amount of power out of it." Dr. Arcot was smiling amusedly at his son. "I can't very well control this except by standing directly in front of it, but I suppose you know what you're doing."

	"Oh, this is a laboratory model, and I haven't gotten the thing into shape really. Look at the conductors that lead to the coil; they certainly aren't carrying ten K.W."

-

	DR. ARCOT slowly rotated the rheostat. There was a slight hum from the coil; then it was gone. There seemed to be no result. He rotated it a bit more; there was a slight draught in the room apparently, but he could see no startling results, so he rotated the rheostat considerably more. This time there was absolutely no doubt as to the results. There was a roar like a fifty-foot wind tunnel, and a mighty blast of cold air swept out of that coil like a six-inch model of a Kansas cyclone. Every loose piece of paper in the laboratory was driving madly before the blast of air that had suddenly leapt out. Dr. Arcot was forced back as by a giant hand, but in reeling back his hand was lifted from the relay switch, and with a thud it had opened the circuit. In an instant all the noise was gone, and only a slight drifting of the air in the room told of the blast that had stirred it up so.

	The astonished physicist came forward and looked at it a moment in silence, while each of the other men watched him. Finally he turned to his son, who was smiling at him with a bit of a twinkle in his eye.

	"Dick, I think you have 'loaded the dice' in a way that is even more lucrative than any other method ever invented! If the principle of this machine is what I think it is, you have certainly solved the secret of a sufficiently absorbing area for a solar engine."

	"Well," remarked the elder Morey, shivering a bit in the chill air of the room, "loaded dice have long been noted for their ability to make money; but I don't see how that explains that working model of an Arctic tornado. Brrr—it is still too cold in here. I think he will need considerable area for heat absorption from the sun, for that engine certainly does cool things down! What is the secret?"

	"The principle is easy enough, but I had considerable difficulty with the application. I think it is going to be rather important though—"

	"Rather important," broke in the inventor's father. "I should think it will be considerably more than that! It is the biggest thing since the electric dynamo! It puts airplanes in the junk heap! It means a new era in power generation. It makes it certain that we will never have to worry about power! It will make interplanetary travel not only possible, but commercially economical."

	"Dad seems to think it is a marvelous machine! But, seriously, I believe it will antiquate all types of airplanes. It is a direct utilization of the energy that the sun is kindly supplying. For a good many years now men have been trying to find out how to release the energy of atoms, or more powerful yet, the energy of constitution of matter. It always reminded me of experimenting with fire on a pile of gunpowder. Of course you could stand there holding the match quite safely, but if someone burned his fingers and dropped the match—

	"But why do it at all? The sun is doing it already, and on a scale so gargantuan that we could never hope nor desire to approach it. Three million tons of matter go into that colossal furnace every second of time, and out of that comes two and a half decillion ergs of energy* (*2,500,000,000,000,000,000,000,000,000,000,000 = 2.5 decilion.). With a total of two and a half million billion billion billions of ergs to draw on, man will have nothing to worry about for a good many years to come! That represents a flood of power vaster than man could comprehend. It would fuse the earth so quickly, you wouldn't have a chance to worry about the hot weather! Why try to release any more energy? We have all that to use; we may as well tap that vast ocean of power.

	"We have been doing that to an extent. Plants have done it for countless ages and more recently man has imitated by absorbing the power from the ocean's heat. But I would hate to estimate their efficiency. The solar engines developed so far are more efficient, of course; they run as high as thirty per cent, but as Dad says, they are tremendously bulky, only dirigibles can use them, and then they are effective only during the day. Dad has told you we need a larger heat absorbing area, and also, if it is going to work during the night, we must have some means of storing the heat energy to use after Sunset Now I think the earth would make a very nice storage basin; it certainly has a very comfortable area. And furthermore, it has a nice thick blanket of air and water that hold a tremendous amount of heat for night use. But it has always been a little hard to use that energy as we wish, though it is all there—more than we can use. But just try and get that energy out! Just think of the terrific amount of power there is stored in the millions of tons of water on the earth. There is only one thing that prevents us getting it out, the law of probability. That's why Dad mentioned loaded dice, for dice, as you know, are the classical example of probability when they aren't loaded. Once they are loaded, the law still holds, but the conditions are now so changed that it will make the problem quite different. Still the law holds. I'll admit that dice always seem to show the wrong face, but with a very great number of trials each face will show an equal number of times. The more trials you make, the more nearly does this approach to exactitude. Similarly there are many other illustrations of the law of probability. If you take an infinite number of chances, it always works out, but if you take any finite number of chances, it won't.

	"The ideal case of an infinite number of chances is very nearly approached in one instance.

	"Molecules in matter which has any heat at all, are moving rapidly, colliding, rebounding, and moving off. There are immense numbers of molecules in the tiniest grain of dust your eye. can see. When you consider the conditions in a liter of helium gas in a container, you can consider that there are an infinite number of molecules in it, to all practical purposes. In it, then, there is an equal chance for any molecule to go in any one direction, and the chances are that there is an equal number of molecules going in each direction. Thus we have our helium gas composed of a tremendous number of molecules, each dashing along at several miles a second, and an equal number dashing in the opposite direction at an equal speed. They are so thickly packed iu there, that none of them can go very far before it runs into another molecule and bounces off in a new direction. But there is a chance that all the molecules should happen to move in the. same direction at the same time. How good is this chance? One of the. old physicists of Einstein's time, a man named Eddington, expressed it very well when he said:

-
	'If an army of monkeys were playing on typewriters they might write all the books in the British Museum. The chance of their doing so is decidedly more favorable than the chance that all the molecules in a liter of gas should move in the same direction at the same time.'
-

The very improbability of this chance is the thing that is making our problem appear impossible.

	"But similarly it would be improbable—impossible according to the law of chance—to throw a string of aces indefinitely, or that one should deal a deck of cards and always deal thirteen of a kind in each hand. It is impossible—unless some other force influences the happening. I f the dice have bits of iridium stuck under the six spots, they will throw aces. If the cards are stacked, they will always deal thirteen of a kind. Chance makes it impossible to have all the molecules of gas move in the same direction at the same tune—unless we stack the chances. If we can find some way to influence them, they may do so.

	"What would happen to a metal bar if all the molecules in it decided to move in the same direction at the same time? Their heat motion is normally carrying them about at a rate of several miles a second, and if now we have them all go one way, the entire bar must move in that direction, and it will start off at a velocity as great as the velocity of the individual molecules. But now, if we attach the bar to a heavy car, it will try to start off, but will be forced to drag the car with it. and so will not be able to have its molecules moving at the same rate. They will be slowed down in starting the mass of the car. But slow molecules have a definite physical significance, molecules move because of temperature, and lack of motion means lack of heat. These molecules that have been slowed down are then cold; they will absorb heat from the air about them, and since the molecule of hydrogen gas at room temperature is moving at about seven miles a second, when the molecules of the confined gas in our car, or the molecules of the metal bar are slowed down to but a few hundred miles an hour, their temperature drops to some hundreds of degrees below zero, and they absorb energy very rapidly, for the greater the difference in temperature, the greater the rate of heat absorption. Of course, in running our machine we must exercise caution, for the bar will try to start off at the full speed instantly, and fastened or not, that is the speed it will go unless its power is applied gradually.

	"In practice I think it will be best to use helium in a copper container, since helium has a very low freezing point, and having a very light molecule, it goes at very high speeds when at room temperature. The copper will carry the heat to it better than any other metal, and that will permit the use of absorbing fins.

	"We will be able to accelerate the car very rapidly to a speed of several miles a second at very high altitudes no doubt, and as we will be able to use a perfectly enclosed streamlined car, we will be able to get tremendous speeds. We will need no wings, of course, for by just putting a small unit pointed vertically, we will be able to support the car in the air. It will make possible a machine that will be able to fly in reverse and so come to a quick stop. It will steer us or it will supply us with electrical power, for we merely have to put a series of small metal bars about the circumference of the generator, and get a tremendously powerful engine. For ground cars, where speeds of over one hundred and fifty miles an hour are impractical, we will use a metal bar, as that is so much more directable, and less subject to gas leaks and failures, though there will be little chance of either in a welded inch-thick copper power unit.

	"But for our present need, it means a tremendously powerful engine, that we can make invisible.

	"I believe you can guess the source of that breeze we had there? It would make a great device for cooling and ventilating theaters and apartments!"

	"Bill Arcot," began Morey, "I would like to be able to use that invention. I know enough of the economics of the thing, if not enough of the science, to know that the apparatus before us is absolutely invaluable. I could not offer to buy the rights on it, but I want to use it if you will let me. It means a new thing in transcontinental airliners! Fuller, I want you to help Arcot with his problem for the ship to chase the Pirate. I will give you the contract to design the new airliners. It will cost us billions to get those new machines out, but there will be no fuel bills, no oil bills, and the cost of operation will be negligible. Nothing but the Arcot short wave tubes to buy—and each one is good for twenty-five thousand hours service!"

	"You will get the rights on this if you want them naturally," said Arcot. "You are maintaining these laboratories for me, and your son here helped me work it out. But if Fuller can move over here tomorrow, it will help things a lot. Also I would like to have some of your best special mechanics to make the necessary machines, and to start the power units."

	"Bill," replied Morey, "you know that these labs are yours, and anything developed in them is yours, and that Dick is officially one of your employees. I will have the men here tomorrow. Do you want to keep this invention secret?"

	"Why I only did some mathematics. But I do think it would be best to keep it a secret, because if the Pirate hears about it, he may get cautious and quit his work," Dick pointed out.

	"I hadn't particularly intended to keep it a secret, but I guess you are right, Dick."

-

	EARLY the next morning Fuller moved his materials over to the laboratory, and set up his table for work. Then, with the aid of Arcot and Morey, the design of the new machine was begun.

	"First, let's get some idea of the most advisable shape," Fuller said. "We will want a streamlined shape; roughly speaking, a cylindrical shape modified to fit the special uses to which it will be put. You no doubt have more of the general plan in mind, Arcot. Suppose you sketch it for us."

	"Well, I thought it would be best to design it also as an experimental ship. We don't know much about this yet, and we have to work it out. You will have plenty of fun figuring out strains in this machine, so let's be safe and use a factor of safety of 5. That will also give us a heavier machine to do the testing with."

	"In the first place, it must be proof against the Pirate's gas, for we won't be following the regular lanes with instruments to guide us safely, if we go out. I have thought that over, and I think that the best system is just what we used in the sample bottles—a vacuum. His gas is stopped by nothing, so to speak, but there is no substance that will stop it! It will no doubt penetrate the outer shell, but on reaching the vacuum, it will tend to stay there, between the inner and outer walls. Here it will tend to collect, since it will be fighting air pressure in its attempts to go either in or out. The pressure inside will force it back, and the pressure outside will force it in. If we did not pump it out, it would soon build up pressure enough to penetrate the interior wall. Now, since the stuff can leak through any material, what kind of a pump shall we use? It won't be pushed by a piston, for it will leak through either the cylinder walls or the piston. A centrifugal pump would be equally ineffective. The obvious solution is a mercury vapor pump, which will, of course, take it out, and keep a high vacuum, the difficulty thing that that kind of a pump has too low a volume of rating. We never would make any progress. The thing would be impossible but for our new machine. With it we can just have a number of openings in the wall of the outer shell and set in them, one of these molecular motion directors, and direct the molecules out! They can't come in through it, and they will tend to go out. That will protect us from the Pirate's gas.

	"But now comes another difficulty. If we protect ourselves against the Pirate's gas by a vacuum, we must remember that our vacuum is an equally good protection against heat! Since our generator is intended to run on heat energy, it will be rather chilly inside if we don't remedy that. Of course, our power units will he placed outside, where the blast of air will warm them, but we really won't have a very good streamline effect if we hang a big electric generator outside. The solution is obvious—if we can't bring the generator to the air, we must bring the air to it. We will have all the power equipment in this room here in the back, and the control room up in front, here. The relays for controlling will be back here, so we can control electrically the operation of the power equipment from our warm, gas-tight room. If it gets too warm in there, we can cool it by using a little of the heat to help accelerate the ship. If it is too cold, we can turn on an electric heater run by the generator. The air for the generator can come in through a small sort of scoop on top, and leave through a small opening in the rear. The vacuum at the tail will assure us a very rapid circulation, even if the centrifugal pump action of the enclosed generator isn't enough.

	"For experimental purposes we will want the generator to be greatly over power so that we can make tests over a greater range. I don't believe we will need more than one hundred kilowatts altogether, but we should install about a thousand, for convenience—A.C., of course, so we can send it through transformers. We will need batteries in the keel for starting the generator. Once the speed is high enough, it will be self-supporting, but it can have a small auxiliary D.C. machine to recharge the batteries and to run the relays. About ten kilowatts will do there.

	"But let's begin making actual figures on this."

	For the rest of the day the three men were working on the general plan of the new ship, trying to calculate the strengths needed, supplementing mathematics with actual experiments with the machines on hand. It was decided to put the batteries inside the main control room, lest they freeze at extreme altitudes.

	It would be two days before they had finished. The calculating machines were busy continuously, for here there were few rules that experience could give them. They were developing something entirely new, and though they had as a designing staff three of the foremost mathematicians in the world it was a problem that tested them to the utmost

	By the evening of the first day, however, they had been able to give the finished designs for the power units to the mechanics who were to make them. The order for the storage battery and the standard electrical equipment had been placed at once. By the time they had completed the drawings for the main castings, the materials were already being assembled in a little private camp that Morey owned, up in the hills of Vermont. The giant freight helicopters could land readily in the wide field that had been cleared on the small plateau, in the center of which nestled a little blue lake and a winding trout brook.

	The mechanics and electrical engineers had been sent up there already—officially on vacation. The entire program could be carried out without attracting the least attention, for such orders from the great Transcontinental lines were so frequent that no importance was attached to them.

	Four days after the final plans had been completed the last of the supplies were being assembled in the portable metal shed that was to house the completed machine. The shining tungsto-steel alloy frame members were rapidly being welded in place by the cathode ray welding torches in the hands of skilled artisans.

	Already at the other end of the shop the generator had been arranged for use with the molecular motion power units. The many power units to drive and support the ship were finished and waiting installment as the party quit work on that fourth evening. They would be installed on the frame in the morning, and the generator would be hoisted into place with the small portable crane. The storage batteries were connected up, and in place in the hull. The great fused quartz windows were resting in their cases on one side of the room, waiting the complete application of the steel alloy plates. They were to be over an inch thick, an unnecessary thickness, perhaps, but they had no need to economize weight, as witnessed by their choice of steel instead of light metal alloys throughout the construction.

	The three men had arrived late that afternoon in a small helicopter, and had gone directly to the shops to see what progress had been made. They had been forced to remain in New York to superintend the shipment of the necessary supplies to the camp site, and since no trouble was anticipated in the making of the steel framework, they had not felt it necessary to come. But now they would be able to help, and to superintend the more delicate work.

	"She is shaping up nicely, isn't she!" Arcot was gazing at the rapidly rounding frame with a critical eye. Unhindered as they were by the traditional shapes, by wings or other protuberances, they had been able to design a machine of striking beauty. The ship was to be left in the natural shiny metal, the only protection being a coat of the newly discovered "passivity paint"—a liquid chemical that could be brushed or sprayed on iron, chromium, nickel or cobalt alloys rendering them passive to practically all chemical agents. Iron can be rendered "passive" by treating in very concentrated nitric acid, the result being a piece of iron that is unattacked by nitric acid, sulphuric, or even aqua regia, which will dissolve gold and platinum, and to a certain extent, iridium. This new "paint" produced a much more permanent passivity in iron, leaving the iron or steel as shiny as ever, but overcast with a beautiful iridescence, and immune to the most powerful reagents.

-

	THE three men walked around the rapidly growing hull, and looked with excited interest at the heavy welded joints and the great beams. The ship seemed capable of withstanding a fall of several hundred feet with little damage. The location of the power units was plainly visible, and easily recognized, for at each point there came together four or five great beams, welded into one great mass of tough metal, and in it there were set the heavy tungsten bolts that would hold the units in place. Stronger than steel, tungsten had a great advantage here, for its long fibrous structure made it peculiarly resistant to shearing strains.

	They inspected each joint minutely for signs of flaws, using a small portable X-ray fluoroscope to see the interior of the metal. Each joint seemed perfect. They retired, satisfied everything was ready for the work of the next day.

	The morning began early with a long swim in the lake, and a hearty breakfast of country farm produce, a thing rare to these city-bred men. Then the work on the great framework was continued, and that day saw the power units bolted in place, removable if change was thought advisable. Each power unit was equipped with long streamlined copper fins lying close to the rounded hull, that they might absorb heat more rapidly.

	Day by day the structure neared completion, and, with the large crew of specially skilled workers, the machine was practically complete within a week. Only the instruments remained to be installed. Then at last even these had been put in place, and with the aid of Fuller, Morey, junior, and Ids own father, Arcot had connected their many complicated circuits.

	"Son," remarked Arcot's father, looking critically at the great switchboard, with its maze of connections, its many rheostats and controls, and its heavy busbar connectors behind it, "any man who can keep his eye on those instruments must be a close relative of the insects with their many-faceted eyes. I certainly hope you have a good-sized crew to operate all those controls! We have spent two days of hard work getting all those circuits together, and I'll admit that some of them still have me beat. I don't see how you intend to watch all those instruments, and at the same time have any idea what's going on outside."

	"Oh," laughed Arcot, junior, "these aren't intended for constant watching. They are merely to aid in efficiency tests and tests of different kinds. I will set the controls for ordinary work, but first I will have to experiment to determine at what values they will work best. I want to experiment with this machine so I can determine the necessary powers and the lowest factor of safety to use in building other machines. I want to use this as a flying laboratory for the necessary experiments. The machine is very nearly completed now. All we need is the seats—they are to be special air-inflated gyroscopically controlled seats, to make it impossible for a sudden twist of the ship to put the strain in the wrong direction. Of course the main gyroscopes will balance the ship laterally, horizontally and vertically, but each chair will have a separate gyroscopic mounting for safety. I want you to remember that this is an experimental model, and not the finished ship. No machine, in all the history of invention, was truly perfected by any one man. I have had the thoughts of four men helping me on this, and the practical suggestions of experienced mechanics, the ideas of old workers, and I believe that the machine will function perfectly, but I want to be able to watch the working of every smallest piece of the structure.

	"I will practice the manipulation of the machine for at least four days before I try to chase the Pirate. I would ordinarily recommend the greatest haste, but the man has stolen close to ten millions now, and is still at it. That would not be done by anyone in his right mind. Just think, the War Department thought that gas so important that they have obtained a pardon for him on condition they he permitted to have the secret of it. They demand the return of the money, and I have no doubt he has it. I am firmly convinced that he is a kleptomaniac. I doubt greatly if he will stop taking money before he is caught. Therefore it will be safe to wait until we can be sure of our ability to operate the machine smoothly. To start out without practice when we are operating such a tremendously powerful airship would be suicidal. Also, I am having some of those tool-makers make up a special type of molecular motion machine for use as a machine gun. The bullets are steel, about three inches long, and as thick as my thumb. They will be perfectly streamlined, except for a little stabilizer at the tail, to act as a guider. They will not spin as a rifle bullet does, and so there will be no gyroscopic effect to hold them nose on, but the streamlining and the stabilizer will keep them on their course. I expect them to be able to walk right through many inches of armor plate, since they will have a velocity of over four miles a second.

	"They will be fed in at the rate of about two hundred a minute—faster if I wish, and started by a small spring. They will instantly come into the field of a powerful molecular motion-director, and will at once be shot out with terrific speed. It will be the first rifle ever made that could shoot bullets absolutely parallel to the ground. The bullets would go on forever without hitting the earth if I shot them when up above the air, for they will follow an orbit! At five miles a second, a thing is in equilibrium between centrifugal force tending to throw it away from the earth, and gravity tending to pull it down, as you know. It will be accurate at all ranges, allowing for wind-carriage only.

	"But that is all we can do today. The guns will be mounted outside, and controlled electrically, and the charts will be installed tomorrow. By the day after tomorrow at eight A. M. we ought to take off!"

	Later that evening they strolled down for a last swim, for strong moonlight was flooding the Vermont countryside.

	As they returned from the swim, Morey noticed that Arcot was standing off to one side looking up at the moon.

	"Thinking of visiting the moon, Dick? I wonder if you could?"

	"I don't know, Bill—but—it isn't impossible now!"

	The work the next day was rushed to completion far earlier than Arcot had dared to hope. All the men had been kept isolated at the farm, lest they accidentally spread the news of the new machine. It was with excited interest that they helped the machine to completion. The guns had not been mounted as yet, but that could wait. Three-thirty of the afternoon found the machine resting in the great construction shed, completely equipped and ready to fly!

	"Dick," said Morey as he strode up to him after testing the last of the gyroscopic seats, "she's ready to fly! I certainly want to get her going—it is only three-thirty, and we can go around to the sunlight part of the world when it gets dark at the speeds we can travel. Let's test her out now!"

	"I have sent for a U. S. Air Inspector. As soon as he comes we can start. I will have to put an 'X' license indication on her now. He will go with us to test it. There will be room for three other people aboard, and I think that you and Dad and I will be the logical passengers. Look, there is a Government helicopter coming. I guess we will start soon. Tell the men to get the blocks out from under it and tow it out on the rollers. Get it at least ten feet beyond the end of the hangar. We will start it straight up, and climb up to at least five miles, where we will have room to make mistakes safely. When we learn to operate this thing, we want to remember that the machine is infinitely more powerful than anything cither of us ever laid our hands on before. While you are tending to that, I will see if I can induce the Air Inspector to take a trip with us."

	Half an hour later the machine had been rolled entirely out of the shed. The great rollers sank deep into the soft turf of the soil as the two-hundred-ton burden pressed down on them.

-

	THE great machine was a thing of beauty as it rested in the bright sunlight. For the first time the machine was out of the dimness of the construction shed, and its true features and lines were apparent. The four men who were to ride in it on its maiden voyage were off to one side looking at the great-gleaming metal hull. The long sweeping lines of the sides told a story of perfect streamline, and implied high speed, even when it rested thus inert on the ground. The bright, slightly iridescent steel hull shone in silvery contrast to the gleaming copper of the power units' heat-absorption fins. The great clear windows in the nose and the low, streamlined air intake for the generator seemed only to accentuate the lines of the graceful machine.

	"Lord, she's beautiful, isn't she, Dick!" exclaimed Morey, looking at the glistening hull.

	"Well, she did shape up nicely on paper, too, didn't she. Oh, Fuller, come and look at your masterpiece. It is even better looking than we thought, now the copper has added color to it. Doesn't she look fast? I wish we didn't need physicists so badly on this trip, so you could go on the first ride with us."

	"Oh, that's all right, Dick, I know the number of instruments in there, and I realize they will mean a lot of work this trip. I wish you all luck. The honor of having designed the first ship like that, the first heavier than air ship that ever flew without wings or helicopter propellers—that is something to remember. And I think it is one of the most beautiful that ever flew, too."

	"Well, Dick," said his father, "let's get under way. I am anxious for the test."

	The four men entered the ship and were strapped in the gyroscopic seats. One by one they reported ready.

	"Officer, I want to explain that these seats may seem to be a bit more active than one generally expects a seat to be, but in this experimental machine, I have provided all the safety devices I could think of. The ship itself won't fail, of that I am sure, but the power is so great it might well prove fatal to us if we are not in a position to resist the forces. You know all too well the effect of sharp turns at high speed and the results of the centrifugal force. This machine can develop such tremendous power that I have to make provision for it. You notice that my controls and the instruments are mounted on the arm of the chair really; that permits me to maintain complete control of the ship at all times, and still permits my chair to remain perpendicular to the forces. The gyroscopes in the base here cause the entire chair to remain stable if the ship rolls, but the chair can continue to revolve about this bearing here so that we will not be forced out of our seats. We will always be 'sitting up' and never lying down or leaning back, as we would seem to be, if the chairs did not vary in position with the forces. The air inflation makes them more comfortable. I sincerely hope you will find the machine safe enough for a license. I know the necessary maneuvers required by law, but I am not used to handling this ship, and I will have to take it straight up first. There is no one in the vicinity to be hurt by any accidents, so with your permission, I will start."

	"All right, Dr. Arcot. If you and your father are willing to try it, I am," replied the Air Inspector.

	"Ready, Engineer"?" asked Arcot.

	"Ready, Pilot!" replied Morey.

	''All right—just keep your eye on the meters, Dad, as I turn on the system. If the instruments back there don't take care of everything, and you see one flash over the red mark—yank open the main circuit. I'll call out what to watch as I turn them on."

	"I am ready, Son."

	"Main gyroscopes!" There was a low snap, a eliciting of relays in the roar compartment, and then a low hum that quickly ran up the scale. "Main generators!" Again the clicking switch, and the relays thudding into action, again the rising hum. "Seat-gyroscopes." The low click was succeeded by a quick scream that died in inaudibly high frequency as the separate seat-gyroscopes took up their work. "Main power tube bank!" The low hum of the generator behind changed to a momentary roar as the relays threw the load on. In a moment the automatic controls had brought it up to speed.

	"Everything is working perfectly so far. Are we ready to start now, Son?"

	"Main vertical power units!" The great ship trembled throughout its length as the lift of the power units began to pull on it. A special instrument had been rigged temporarily on the floor beside Arcot, that he might be able to judge the lift of his power units; it registered the apparent weight of the ship. It had read two hundred. Now all eyes were fixed on it, as the pointer dropped quickly to 150—100—75—50—40—20—10—there was a click and the instrument flipped back to 300—it was registering in pounds now! Then the needle was at zero, and the mighty structure floated into the air, slowly moving down the field as a breeze carried it along the ground. Now the men outside saw it rise swiftly into the sky, straight toward the blue vault of heaven. In two or three minutes it was disappearing. The glistening ship shrank to a tiny point of light; then it was gone! It must have been rising at fully three hundred miles an hour! The fastest racing helicopters seldom rose faster than that! The record was three hundred and thirty-two miles an hour!

	To the men in the car there had been a tremendous increase in weight that had forced them into the air cushions like leaden masses. Then the ground was dropping away with a speed that made them look in amazement. The house, the construction shed, the lake, all seemed contracting beneath them. So quickly were they rising that they had not had time to adjust their mental attitude. To them all the world seemed shrinking about them. Now they were at a tremendous height, over twenty miles they had risen into the atmosphere; the air about them was so thin that the sky-seemed black, the stars glazed out in cold, unwinking glory, while the great fires of the sun seemed reaching out into space like mighty arms reaching—reaching to draw back to the parent body the masses of the wheeling planets. About it, in far flung streamers of cold fire the mighty zodiacal light stretched out into space, an Aurora on a titanic scale. For a moment they hung there, while they made readings of the meters.

	"I never began to let out the power of this thing. When these are made commercially, we will have to use about one horsepower generators in them, or people will try to see how fast it will go and will die of the terrific acceleration and leave the car, like some vast bullet, streaking on through the sky at ever greater speeds, till at last it throws itself off into space. This would make it a menace as well as a blessing. I will have to be careful myself!"

-

	FOR several minutes the machine was tried out at this height, testing various settings of the instruments. It was definitely proven that the values that Arcot and Morey had assigned from purely theoretical calculations were correct to within one-tenth of one per cent. The power absorbed by the machine they knew and had calculated, but the terrific power of the driving units was far beyond their expectations. They had estimated the power of the machine as great, but even they had been unable to calculate the power released.

	"Well, now we're off for some horizontal maneuvers. I believe I have satisfactorily demonstrated the machine's ability to hold itself in the air, to climb at a safe rate to a considerable altitude. The air pressure controls seem to be working perfectly. I am now going to give the necessary proof of ability to maintain traffic speed—I believe they now require over two hundred miles an hour. I will accelerate it at the greatest safe value."

	Suddenly the seats swung beneath them a bit; then, as the ship shot forward with ever greater speed, ever greater acceleration, it seemed that it turned and headed upward, although they knew that the main stabilizing gyroscopes were holding it level. The seats swung beneath them as the acceleration became greater and greater. In a moment the ship was headed out over the Atlantic at a speed no rifle bullet had ever known. Faster and faster the plane streaked along, until it became an almost invisible blur. The radio speedometer needle pushed farther and farther over as the speed increased to unheard of values. Before they left the North American shoreline they were going over one mile a second. The speed increased terrifically, as the men labored under weights of seven to eight hundred pounds apiece. They were over the middle of the Atlantic before Arcot gradually shut off the acceleration, letting the seats drop back into position. Once more they were able to judge up and down with some definite standard.

	They had been able to watch the sun sink rapidly toward the horizon. It was night on the water rolling far beneath, but the sun's rays still reached them where they were.

	"What speed did we reach, Dr. Arcot—look—there is the coast of Europe. Watch it come toward us. How fast are we going?" asked the Air Inspector.

	"The air resistance is slowing us down. We were traveling at the rate of three miles a second before I decreased the acceleration. Now it has fallen to two and a half!" Dr. Arcot answered.

	"That decidedly checks off the speed requirement. But how do you measure such terrific speed? You have no means of using the air blast at that rate. What is the system?"

	"I had to develop one—but it is only accurate to about one part in a hundred now. That's near enough for our work. For ordinary speeds we use the automatically barometrically corrected airspeedometer, but this piece of apparatus depends on the use of radio. You do not change the speed of light no matter how fast the source is moving, but for that reason, if the source is moving toward you, the waves get packed in closer together than they would ordinarily. The same is true of a radio wave. I send out a radio wave from a very small set in the nose of the ship, and pick it up by a set in the rear of the ship. By means of the usual velocity measuring apparatus I find the velocity of the wave as picked up by the set in the rear. That is electrically registered here, but instead of registering it as 186,285 miles per second, with the appropriate number of tenths and hundredths of a mile per second, it subtracts the discovered value from the correct value, the difference being, our speed. I hope to get it more accurate in the future, but it is the only serviceable means at hand now.

	"I'm going to try to see what the ultimate ceiling of this machine is. Remember, it must have a ceiling, since it depends on the operation of the generator to operate the power units. This, in turn, depends on the heat of air. Of course the main power units, being outside in the sun's rays, are warmed to an extent by them. I don't know how high it will work."

	The ship was put into a vertical climb, and steadily the great machine rose, at a low rate lest they overshoot the mark, and have the wrong result. Soon, however, the great generator behind began to slow down, the automatic controls could not bring it up to a sufficient speed. The readings of the instruments were dropping rapidly. The temperature of the exceedingly tenuous air outside was so close to absolute zero that it was nearly impossible to get sufficient energy from it.

	"Get up some forward speed so that you will have the aid of the air scoop to force the air in faster."

	"Right, Morey." Arcot slowly applied the power to the forward propulsion units. Slowly they took hold, and the ship began to move forward again. The increase was apparent at once. The machine quickly gained power and she was rising again. But at last, at a height of fifty-one miles, the ship would rise no farther. The cold of the cabin became unbearable, for every kilowatt of power that the generator could get from the air outside was needed to run the power units. The air, too, was getting bad, for the pumps could not supply enough, and the oxygen tanks had not been carried on this trip. Now they were dropping, dropping, the machine was held stable by the gyroscopes, but she was dropping freely, the power of the generator being used to warm the cabin once more. But the machine had fifty miles to fall, and as the air resistance of the denser air mounted, they could begin to feel the weight return as the air slowed them down in their fall.

	"You've passed, but for the maneuvers, sir! The required altitude was passed so long ago—why we are still some miles above it, I guess! How fast are we falling?" The Air Inspector was decidedly impressed.

	"I can't tell unless I point the nose of the ship down, for the apparatus works only in the direction in which the ship is pointed. Hold on, everyone, I am going to start using some power to stop us."

	It was night when they returned to the little field in Vermont. They had established a new record in every form of aeronautical achievement except endurance! The altitude record, the speed record, the speed of climb, the acceleration record—all that Arcot could think of had been passed. Now the ship was coming to dock for the night. In the morning it would be out again. But now Arcot was sufficiently expert with the controls to maneuver the ship safely into the hangar. They finally solved the wind difficulty by decreasing the weight of the ship to about fifty pounds, so enabling the three men to carry it into the hangar!

-

	THE next two days were devoted to careful tests of the power factors of the machine, the best operating frequency, the most efficient altitude of operation, and as many other tests as they had time for. Each of the three younger men took turns operating it, but so great were the strains of the sudden acceleration, that Arcot, senior, decided it would be wisest to stay on the ground and watch.

	In the meantime reports of the Pirate became fewer and fewer as less and less money was shipped by air.

	Arcot spent four days practicing the manipulation of the machine, for though it handled far more readily than any other machine he had ever controlled, there was the danger of turning on too much power under the stress of sudden excitement. Yet he could not afford to lower the limit of available power, for there must be a margin of at least 32 feet per second to cover the effects of gravity.

	If they were flying against it, they would need 64 feet per second per second more acceleration than if they were flying with it. The "feel" of the ship could be gotten by practice only. He must make his actions instinctively in emergencies, and the battle with the Pirate was apt to be a long series of emergencies, for certainly the Pirate had some weapons other than his gas. No standard machine gun could throw a bullet through the inch-thick armor-plate walls of the machine, and as these were double, there was slight chance of any known ship carrying a gun heavy enough to pierce these double walls, which were yet light enough to land on the Transcontinental plane without disturbing its equilibrium.

	The night before, Arcot had sailed the ship down and alighted on the roof of Morey senior's apartment, leaving enough power on to reduce the weight to but ten tons, lest it fall through the roof, while he went down to see the President of the Lines about some "bait" for the Pirate.

	"Send some cash along," said Arcot, when he saw Morey, Sr. "Say a quarter of a million, make it more or less public knowledge, and talk it up so that the Pirate may think there is a real haul on board. I am going to accompany the plane at a height of about a quarter of a mile above. I will try to locate him from there by means of the radio disturbance locater, and if I have my apparatus on, I naturally can't locate him. I hope he won't be scared away—but I rather believe he won't. At any rate, you won't lose on the try!"

-

	AGAIN Morey and Arcot were looking at the great Jersey aerodrome, out on the great fields that had been broad marshes centuries before. Now they had been filled in, and stretched for miles, a great landing field, close to the great city across the river.

	The men in the car above were watching the field below, hanging inert, a silent dot of glistening metal, high in the deep velvet of the purple sky, for fifteen miles of air separated them from the Transcontinental machine below. Now they saw through their field-glasses that the great machine was lumbering slowly across the field, gaining momentum as it headed westward into the breeze on the take-off. Then it seemed to be barely clearing the great skyscrapers that towered twenty-four hundred feet into the air, arching over four or six city blocks. From this height they were toys made of colored paper, soft colors that glistened in the hot noon sun, and around and about them were weaving lines of flashing, moving helicopters, the individual lost in the mass of the million or so swiftly moving machines, for only the higher, steady moving levels of traffic were visible to them. Below these they knew were other and still other levels of machines, hanging motionless or creeping along at thirty or forty miles an hour, rocking slightly, despite the gyroscopic stabilizers as the terrific air-wash of thousands of whirring blades hit them, varying each moment as the crowded traffic moved.

	"Just look at those cars in the traffic below there! Thousands and thousands coming back into the city after going home to lunch—and every day the number of helicopters is increasing! If it hadn't been for your invention of this machine, they would have been impossible soon. The airblast in the cities is unbearable now, and getting worse all the time. Many machines can't get enough power to hold themselves up at the middle levels; there is a down current of over one hundred miles an hour at the 400-foot level in downtown New York. It takes a racer to climb fast there!

	"If it were not for the gyroscopic stabilizers, they could never live in that huge air-pocket. I have to drive in through there. I'm always afraid that somebody with an old worn-out bus will have stabilizer failure, and it will work havoc with hundreds below." Morey was a skillful pilot, and realized, as few others did, the dangers of that downward airblast that the countless whirring blades maintained in a constant roar of air. The office buildings now had double walls, with thick layers of sound-absorbing materials, to stop the roar of the cyclonic blast that continued almost unabated twelve hours a day.

	"Oh. I don't know about that, Morey," replied Arcot. "This thing isn't all to the good. Remember that if we had about ten million machines hung in the air of New York City on the heat contained, there would be a noticeable fall in the temperature. It would undoubtedly drop to a temperature that would produce an Arctic climate year in and year out. You know, though, how unbearably hot it gets in the City by noon, even on the coldest winter days, due to the heating effect of the air friction of all the thousands of blades. I have known the temperature of the air to go up fifty degrees, due to the heat of the engines and the friction of the blades. The solution of the thing is obvious. There will be a sort of balance between the two types of machines. It will be a terrific economical problem, but at the same time it will solve the problem of the great companies who have been fermenting grain residues for alcohol. The castor bean growers are also going to bring down their prices a lot when this machine kills the market. They will also be more anxious to extract the carbon from the cornstalks for reducing ores of iron and of other metals. It will no doubt have to be worked out eventually at any rate." As the ship flew high above the Transcontinental plane, the men discussed the economic values of the different applications of Arcot's discoveries from the huge power stations they could make, to the cooling and ventilating of houses.

	"Arcot, you mentioned the cooling effect on New York City; with the millions on millions of these machines that there will be, with huge power plants, with a thousand other different applications in use, will not the terrific drain of energy from the air cause the whole world to become a little cooler?" asked Fuller.

	"I doubt it," said Arcot slowly. "I have thought of that myself. Remember that most of the energy we use eventually ends up as heat anyway. The lights we use turn the electricity to light, whence it is radiated to be absorbed by materials that convert it into heat. Motors give off heat and mechanical energy. The propellers convert the mechanical energy to motion of the molecules of air—heat again. The forward drive of the airship is converted into heat through air-friction. Only the energy we store as chemical energy is maintained—and eventually that leaks back into the air. In return, just remember the decillions of ergs of energy that the sun is giving off—true, we don't get more than an infinitesimal portion of that energy—but what we do get is more than enough for us. Power houses can be established very conveniently in the tropics, where they will cool the air, and the energy can be used to refine metals or to stabilize the carbon of carbon dioxide from the air. I understand from something Dad said last night that that is what he is working on now. He has devised a method for electrolyzing carbon dioxide in a solution in a compound Jackson worked out for him. That brings us to carbon, the true starting point for any organic synthesis. With that we will have an unlimited supply of acetylene, the one indispensable hydro-carbon in modern synthesis. That means that the surplus heat of the tropics will find a use. Together with the weather control possible by the direction-control of great winds, we could set huge director tubes on top of mountains, and blow the winds in whatever direction best suited us, not the blown wind itself, but the vast volume of air it carried with it, would be able to cool the temperate zones in summer from the cold of the poles, and warm it in winter with the heat of the tropics. Similarly the tropics would, in this way, be cooled. Of course the control could not be perfect, but it would bring about a vast improvement. I think, however, that we will find this machine to be of great benefit. I don't think it will appreciably lower the mean temperature of the earth.

	"And there is another thing it may make possible in the future—a thing that is hard to accept as a commercial proposition. We have sources of energy now, but we have no sources of materials that will last indefinitely. Copper is becoming more and more rare. Had it not been for the discoveries of the great copper fields of the Sahara and in Alaska, we would not have any now. Platinum is exhausted, and even iron is becoming more and more valuable, for low-grade iron ores cannot be worked. We are facing a shortage of metals. Aluminum, magnesium, calcium, and iron exist in vast quantities, but they are largely in low concentration ores. Do you realize that within the next two centuries we will be unable to maintain this civilization unless we get new sources of materials? History shows us civilization after civilization falling before the invading hordes of barbarians—men who were better equipped to fight for what they wanted. Within two centuries our civilization will be helpless for lack of essential metals. Iron can be gotten from the frames of the skyscrapers as they are replaced by little glass buildings. Glass, or silicon dioxide, practically constitutes a huge percentage of the earth's crust. Silicon represents 28% and oxygen over 47%, so in the available matter of the earth, two elements alone constitute more than three-quarters of the resources. Luckily, the next most abundant element, and the next few are metals, aluminum, iron, calcium, magnesium, sodium and potassium. (I am not certain about the order of calcium and magnesium.) Together, these total about 23%. That means that the first seven abundant elements constitute 98% of our available resources. All the other elements on earth do not total more than 2%! That means that, including the vast quantities of hydrogen, nitrogen, and all other non-metals, chlorine, sulphur, and even carbon, and many metals such as copper, lead, zinc, tin, silver, tungsten, molybdenum, beryllium—all the other 85 elements—total only two per cent! Every time I think of those figures it frightens me. Aluminum, iron, and magnesium are useful for our work. Calcium, sodium, potassium—we cannot use them; they are soft, and so active that they corrode rapidly in the air. In the 98% of the available matter of the earth, three elements are useful. In the two per cent lie all our other materials, except glass. Well, it looks as if we had better start using glass a great deal more!

	"But we have one other chance now. This civilization is doomed if we don't get more elements from somewhere.

	"The solution is—there are eight*(*Since this story was written, a ninth planet was discovered.) planets in this solar system! Neptune and Uranus are each far vaster than Earth; they are utterly impossible for life as we know it, but a small colony might be established there to refine metals for the distant earth. We might be able to build tight-closed cities. But first we could try the nearer planets—Mars, Venus, or some satellites such as our Moon. I pray that this machine will make it possible."

-

	FOR some time they sat in silence in the machine as they swept along, high above the green plains of Indiana. Chicago lay like some monster jewel far off on the horizon to the right and ahead. Below them the huge bulk of the Transcontinental plane seemed a toy, five miles below, as it swung slowly across the fields—actually traveling over six hundred an hour. They too seemed almost motionless as the landscape swung slowly past beneath them. At last Morey spoke.

	"You are right, Arcot. We will have to think of the interplanetary aspects of this some day. Oh, isn't that Chicago off there? We had better start the vacuum gas protector. And I will turn the radio disturbance indicator on to the general reception aerial till we see some signs of action."

	The three men forgot the impending danger of the shortage of metals. There were a number of adjustments to make, and these were quickly completed, while the machine forged evenly, steadily ahead. The generator was adjusted to the maximum efficiency, the various tubes were tested separately, for though they were all new, and each good for twenty-five thousand hours, it would be inconvenient, to say the least, if one failed while they were in action. Each tested perfect, and though they could not hear the even hum of the generator behind them, due to the approximate vacuum at this altitude, they knew from the smooth functioning of the various relays that governed it as the loads on it varied, that it must be working perfectly, at something less than one-half maximum rating. There was a reassuringly large factor of safety in all parts of this machine, which was a good thing on an experimental machine, but left no factor of safety for Mr. Average Citizen's pocket book, if put on the commercial production in this form.

	Steadily they flew on, waiting tensely for the first sign of a glow from the tiny neon tube indicator on the panel before Morey.

	"This looks familiar, Dick," said Morey, looking about at the fields and the low line of the blue mountains far off on the western horizon. "I think it was about here that we took our little nap in the 'Flying Wheel Chair,' as the papers called it. It would be about here th—LOOK! It is about here! Get ready for action, Fuller. You're taking the machine gun, I'll work the invisibility disrupter, and Arcot will run the ship. Let's go!"

	On the board before him the tiny neon tube flickered dully, glowed for a moment like a piece of red-hot iron, then went out. In a moment it was glowing again, and then quickly its brilliance mounted till it was a line of crimson. Quickly Morey snapped the switch from the general radio disturbance detector to the beam receiver, that he might locate the machine exactly, the receiving set being arranged to pick up the signals emanating from points in the beam only, and the same control kept the projector of the indivisibility disrupter in constant coordination, so that the sighting of the receiver automatically directed the disrupter beam at the same point. Quickly the beam was scanning the sky below them, as it searched for the plane of the Pirate. It was fully a minute before the neon tube flashed into life once more. The pirate was flying just ahead of the big plane, very likely gassing them. All around him were the Air Guardsmen, unaware that the enemy was so near. As the disrupter beam could be projected only about a mile, they would have to dive down on the enemy at once, and an instant later the great plane beneath them seemed to be rushing toward them at terrific speed.

	The two radio beams were constantly kept focused on the plane of the Pirate. When they were about two miles from the two machines below them, the neon tube blazed up brilliantly as the energy of the two machines clashed. The Pirate was trying to maintain his invisibility, while the rapidly growing strength of the machine above was trying to batter it down, the resulting interference radiating a large amount of energy. The strength of Morey's beam was growing at a tremendous rate, as the two machines approached at nearly three hundred miles an hour. In a moment the ammeter connected with the disrupter beam began to rise so rapidly it seemed dangerous, for despite the ten-kilowatt set being used to project the beam, the resistance of the apparatus on board the pirate ship was amazing. Now, however, there was a rapidly solidifying cloud before them, as the interference of the beam Morey was sending broke down the molecular oscillation that permitted the light to pass freely through the machine. Suddenly there was a circle of blue light about the shadow form, and a moment later the ionized air relapsed into normal condition as the pirate's apparatus broke down under the strain. At once Morey shut off his apparatus, convinced from the suddenness that the pirate's apparatus had been blown out, the tubes unable to stand the strain of the larger tubes on board their machine. He glanced up to look at the pirate as he finished his job. He cried out in astonishment as Arcot called to him, "Morey—look at him go!"

	Morey was too late to see him go. Already the plane had shot off with terrific speed. It had shot up and to their left, at a rate of climb that seemed unbelievable—except that the long trail of flaming gas told the story! The plane was propelled by rockets! The terrific acceleration carried it out of their range of vision in an instant, and as Arcot swung the ship to bring him again within the range of the windows, they gasped in astonishment, for already he was many miles away, a long trail of flaming gas marking his swift flight! There was a terrific wrench as Arcot threw on all the power he dared, then quickly leveled the machine out, following the pirate at lightning speed. He increased the acceleration further as the men grew accustomed to the force that weighed them down. Ahead of them the pirate was racing along, but quickly now they were overhauling him, for his machine had wings of a sort! They produced a tremendous amount of head resistance at their present velocity, for already the needle of the radio speedometer had moved over to one mile a second. They were following the fleet plane ahead at the rate of 3600 miles an hour. The roar of the air outside was a tremendous wave of sound, yet to than, protected by the vacuum of the double walls, it was detectable only by the vibration of the car.

	And naturally the rarefaction of the air operated to reduce the sound.

-

	RAPIDLY the lead of the pirate's machine was cut down, as their acceleration became greater. It seemed but a moment before he would be within range of their machine gun. Suddenly he nosed down and shot for the ground, ten miles below, with the full speed of his machine. In an instant Arcot had swung his machine in a loop that held him close to the tail of the pirate. The swift maneuvers at this speed were a terrific strain on both men and machines—the acceleration seemed crushing them with the weight of four men, as Arcot followed the pirate in a wide loop to the right that ended in a straight climb, the power rocket ship standing on its tail, the rocket blast roaring out behind, a stream of fire a half mile long. It was climbing at a speed that would have distanced any other machine the world had ever seen, but the tenacious opponent behind him clung ever tighter to the tiny darting thing. He had released great clouds of his animation suspending gas. To his utter surprise, the ship behind had driven right through it, entirely unaffected! He, who knew most about the gas, had been unable to devise a material to stop it, a mask or a tank to store it, yet in some way these men had succeeded! And that hurtling, bullet-shaped machine behind! Like some miniature airship it was, but with a speed and an acceleration that put even his to shame! It could twist, turn, dive, rise and shoot off on the straight-away with more flashing speed than his machine displayed. Time and again he tried complicated maneuvers that strained him to the utmost, yet that machine always followed after him!

	There was one thing to do. In outer space his rockets would support him. In a straight climb he shot up to the blazing sun above, out into space, while the sky around him grew black, and the stars shone in solemn splendor around him. But he had eyes for only one thing, the shining car that was rising with more than equal speed behind him. He knew he must be climbing over two thousand miles an hour, yet the tracker came ever closer. Just out of sighting range for the machine gun now ... in a moment ... but, she was faltering!

	The men in the machine behind sat white-lipped, tense, as the whirling shocks of sudden turns at terrific speed twisted the gyroscope seats around like peas in a rolling ball. Up, down, left, right, the darting machine ahead was twisting with unbelievable speed. Then suddenly the nose was pointed for the zenith again, and with a great column of flame shooting out behind him, he was heading straight toward space!

	"If he gets there, I lose him, Morey!" said Arcot. The terrific acceleration of the climbing car seemed to press them to their seats with a deadly weight. It was a labor to talk—but still the car ahead was shooting ahead—slowly they seemed to be overhauling him. Now that the velocities were perforce lowered by the effects of gravity, and the air resistance of the atmosphere was well nigh gone, only the acceleration that the human body could stand was considered. The man ahead was pushing his plane ahead with an acceleration that would have killed many men!

	Slowly the acceleration of the machine was falling. Arcot pushed the control over to the last ampere, and felt the slight surge, as greater power rushed through the coils momentarily. Soon this was gone too, as the generator behind faltered. The driving power of the atmospheric heat was gone. More than sixty miles below them they could see the earth as a greenish brown surface, slightly convex, and far to the east they could distinguish a silvery line of water! But they had no eyes but for the column of shooting flame that represented the fleeing raider! Out in airless space now, he was safe from them. They could not follow. Arcot turned the machine once more, parallel to the earth, watching the plane above through the roof window. Slowly the machine sank to the fifty-mile level, where there was just sufficient air to maintain it in efficient operation.

	"Well, he beat us! But there is only one thing for us to do. He must hang there on his rockets till we leave, and we can hang here indefinitely, if we can only keep this cabin decently warm He has no air to cool him, and he has the sun to warm him. The only thing that is worrying him right now is the heat of his rockets. But he can throw most of that out with the gases. Lord, that's some machine! The principle is easy to see. He uses his atomic hydrogen stored in the way he has, and thereby can store, in very little space, a gaseous material that yields 100,000 calories for every two grams. He can run a real machine on that! But eventually his rockets will give out, and down he will come, so we will just hang here beneath him and—whoa—not so fast—he isn't going to stay there, it seems; he is angling his ship off a bit, and shooting along, so that, besides, holding himself up, he is making a little forward progress. We will have to follow! He is going to do some speeding, it seems! Well, we can keep up to him, at our level."

	"Dick, no plane ever made before would have stood the terrific pulls and yanks that his plane got. He was steering and twisting on the standard type air rudders, and what strains he had! That unique type of plane must be extremely strong. I never saw one shaped like his before, though—it is the obvious shape at that! It was just a huge triangular arrowhead! Did you ever see one like it?"

	"Something like it, yes, and so have you. Don't you recognize that as the development of the old paper gliders you used to throw around as a kid? It has the same shape, the triangular wings with the point in the lead, except that he undoubtedly has a slight curve to the wings to increase the efficiency. I hope that man is only a kleptomaniac, because he can be cured of that, and I can then have a new laboratory partner. He has some exceedingly intelligent ideas! His idea of copying the birds was good—except that he carried it too far. The idea of flying was good, but the birds have a method that man can't imitate. The birds have flapping wings, and their wings are shaped to work well when they flap. Man tried for a while to make a machine that would flap its wings. He generally got killed in the attempt. Finally he decided to try having the wings there, just as the birds do, but not flapping them. He tried to imitate the bird in gliding flight. That was rather foolish, for the birds' wings are made to flap, and when they glide, they are using them for a secondary purpose. Man stands on two jointed bone columns, carefully made and fitted together with some of the most wonderful mechanical features we know of. Why not build buildings, and stand them on similar mechanisms? Simply because legs have only a secondary use in supporting members. They were primarily designed for locomotion.

	"Similarly a bird's wings were designed for movement. Then, too, a rotary motion is so much more efficient than a reciprocating motion. The wheel is beyond a doubt a better way to get over ground than the leg. Why didn't Nature use it? A wheel is not such a good thing to climb trees with, and trees are very useful if a saber tooth tiger happens to be in the neighborhood. Evolution did not favor it. Can you imagine a bird with a propeller on its beak? The propeller is more efficient than the flapping wing, but Nature couldn't use it—it was a matter of design. Imagine, if you can, a bird with a bone propeller on its beak—or somewhere, driven by a bone crankshaft, turned, by muscles—muscles arranged like the cylinders of an engine! It just couldn't be done. Nature had to use the flapping wing.

	"And man, seeing the bird fly, decided that was the way to fly. He found he couldn't do it, but it took him hundreds of years to find some other way than merely approximating the bird.

	"Do you remember how the little paper gliders of our school days used to soar and bank and turn with perfect control; they never stalled in the air, never stayed in a nose dive, never went into tail spins and were, structurally strong enough to be made of thin paper. The standard and only figure that is used in bracing things anywhere is the triangle; it is the unit of strength. It can't he deformed as can a square, it is geometrically better. Why not use it! No wonder the pirate's ship would stand the strains he put on it. No wonder it makes an excellent glider. Of course it would.

	"He is an ingenious man, but I wish he didn't store quite so much hydrogen in his rocket tubes! It is unbearably cold in here, and I can't sacrifice any power to heat. it. The rocket ship up there seems to be getting more and more acceleration in the level. He has me dropping steadily to get air to run the generator. He is going fast enough!"

	They followed beneath the pirate, faster and faster as the rockets of the ship began to push it forward more and more.

	"Dick, why is it he didn't use all his rockets at first instead of gradually increasing the power this way?"

	"If you were operating the ship, Morey, you would understand. Look at the speedometer a moment and see if you can figure it out!"

	"Hmm—4.5 miles per second—buzzing right along—but I don't see what that—good Lord! We never will get him at this rate! How do you expect to get him?"

	"I am still in the dark on that subject. But Arcot, I wonder why it is that he doesn't have to use all his rockets!" said Fuller.

	"He is going 4.5 miles a second. When he reaches 5 miles a second he will never come down from his hundred and fifty mile high perch. He will establish an orbit! He has so much centrifugal force already that he has very little weight We are staying right beneath him, so we don't have much either. Well, there he goes in a last spurt. We are falling behind pretty fast—there we are catching up now—no—we are just holding parallel! He's done it! Look!"

-

	ARCOT pulled out his. watch and let go of it. It floated calmly in the air for a moment, then slowly drifted back toward the rear of the room. "I am using a bit of acceleration—a bit more than enough to maintain our speed. We are up high enough to make the air resistance almost nothing, even at this velocity, but we are held back enough to require some power. I don't know—"

	There was a low buzz, repeated twice. Instantly Morey turned the dials of the radio receiving set—again the call signal sounded. In a moment a voice came in—low, but distinct. The power seemed fading rapidly.

	"—am the Pirate—help if you can. Can you get outside the atmosphere? Exceed orbital speed and fall out? Am in an orbit and can't get out. Fuel reserve gage stuck, and used all my rockets. No more power. Can not slow down and fall. I am running out of compressed air and the generator for this set is going—will take animation suspending gas—will you be able to reach me before entering night?"

	"Quick, Morey—answer that we will."

	"We will try, Pirate—think we can make it!"

	"O. K.—power about—now	"

	The last of his power had failed! The pirate was marooned in space! They had seen his rockets go out, leaving the exhaust tube glowing for a moment before it, too, was dark, and only the sun shining on the silvery plane made it visible.

	"We have to hurry if we want to do anything before he reaches night! Radio the San Francisco fields that we will be coming in soon, and we need a large electromagnet—one designed to work on about 500 volts D. C, and some good sized storage cells; how many will have to be decided later, depending on the room we will have for them. I will start to slow down the ship now. We are somewhere west of the Hawaiians, I believe, but we ought to be able to do the trick if we use all the power we can."

	Morey at once set to work with the radio set to raise San Francisco airport. He was soon in communication with them, and told them that he would be there in about one hour. They promised all the necessary materials; also that they would get ready to receive the pirate when he was finally brought in to them.

	"Arcot," asked Fuller, "why don't you just circle around and head back, taking advantage of your speed, instead of killing it in one direction, only to develop more in the other?"

	"The circle I would have to turn in would have to have a thousand mile radius, because any smaller circle would mean a centrifugal force that would be fatal to us. I will be able to turn soon, but I must slow down, first.

	It was nearer an hour and a quarter later that the machine fell to tire great San Francisco landing field, where the mechanics at once set to work bolting a huge electro-magnet on the landing skids on the bottom of the machine. The most serious problem was connecting the terminals electrically without making holes in the hull of the ship. Finally one terminal was grounded, and the radio aerial used as the other. Fuller was left behind on this trip, and a large number of cells were installed in every possible position. In the power room, a hastily arranged motor generator set was arranged, making it possible to rim the entire ship from the batteries. Scarcely had these been battened down to prevent sliding under the accelerations necessary, titan Arcot and Morey were off. The entire operation had required but fifteen minutes.

	"How are you going to catch him, Arcot?"

	"I'll overtake him going west. If I went the other way I'd meet him going at over 10 miles a second in relation to his machine. He had the right idea. He told me to fall out to him at greater than orbital speed. I will go just within the earth's atmosphere till I get just under him, holding myself in the air by means of a downward acceleration on the part of the regular lifting power units. I am going to try to reach eight miles a second. We will be overhauling him at three a second, and the ship will slow down to the right speed in falling out to him. We must reach him before he gets into the shadow of the earth, though, for if he reaches 'night' he will be without heat, and despite the fact that he is in a suspended animation condition, he will die of cold. I think we can reach him, Dick!"

	"I hope so. Those spare cells are all right, aren't they? This acceleration is hard on anything. We will need those! If they don't function when we get out there, we will fall clear off into space! At eight miles a second, we would leave earth forever!"

	"But Dick, I don't see how you can get eight miles a second, when helium atoms at room temperature don't move that fast. They won't drive a car that fast will they?"

	"Right you are Morey—but for one fact. How fast are helium atoms going at room temperature? Earth goes nineteen miles a second, so they must be going fast enough! They are always trying to go just six or seven miles a second faster than we, no matter how fast we go! It will be willing to drive us at eight miles a second. But we don't want to get too high and find the generator won't give power enough to slow us down so we can fall, nor power enough to pull us down against centrifugal force!"

	The ship was accelerating steadily at the highest value the men aboard could stand safely. The needle of the speedometer was creeping steadily across the dial. They were flying at a height of forty miles that they might have enough air and still not be too greatly hindered by air resistance. The black sky above them was spotted with points of glowing light, the blazing stars of space. But as they flew along, the sensation of weight was lost; they had reached orbital speed, and as the car steadily increased its velocity, there came a strange sensation! The earth loomed gigantic above them! Below them shone the sun! The direction of up and down was changed by the terrific speed, the needle of the speedometer was wavering at 7.8 miles a second. Now it held steady!

	"I thought you were going to take it up to eight miles a second, Dick?"

	"Air resistance is too great! I'll have to go higher!"

	At a height of fifty miles they continued at 8.1 miles a second. It seemed hours before they reached the spot where the pirate's machine should be flying directly above them, and they searched the black sky for some sign of the shining dot of light. With the aid of field glasses they found it, far ahead, and nearly one hundred miles above. Things here in the clear space were far more visible than they would have been if seen through the dull atmosphere.

	"Well, here we go! I'm going to fall up the hundred miles or so, till we are right on his path; the work done against gravity will slow us down a little, but I will have to use the power units somewhat. Did you notice what I did to them?"

	"Yes, they were painted a dull black. What was the idea?"

	"We will have no air, from which to get heat for power out here, so we will have to use sunlight. I am using it now to slow us down as much as possible. That, together with the air resistance and the energy needed for raising the car one hundred miles, will be enough to slow us down, I think!"

	At last the tiny silver dot had grown till it took on the form of the plane it was. They were drawing up to it now, slowly, but steadily. At last the little machine was directly beneath them, and a scant hundred yards away. They had long since been forced to run the machine on the storage batteries, and now they applied a little power to the vertical power units. Sluggishly, as they absorbed the sun's heat, the machine was forced lower, nearer to the machine below. At last a scant ten feet separated them.

	"All right, Morey."

-

	THERE was a snap, as the temporary switch was closed, and the current surged into the big magnet on the keel. At once they felt the ship jump a little under the impulse of the magnet's pull on the smaller machine. In a moment the little plane had drifted up to the now idle magnet, touched it and was about to bounce off, when Morey again snapped the switch shut and the two machines were locked firmly together!

	"I've got him, Dick. Now slow it down till it falls. Then we can go and wait for it. Being a glider, it ought to be quite manageable!"

	Now the energy of the power units on the roof of the machine began to slow down the two machines, the magnet grinding slightly as the momentum of the plane was thrust upon it. They watched the speedometer needle drop. The speed was sinking very slowly, for the area of the absorbing fins was not designed to absorb the sun's heat directly, and was very inefficient. The sun was indeed sinking below their horizon; they were just beginning to watch that curious phenomenon of seeing dawn backward, when they first struck air dense enough to operate the power units noticeably. Quickly the power was applied till the machines sank rapidly to the warmer levels, the only governing factor being the tendency of the glider to break loose from the grip of the magnet. 

	At fifty miles the generator was started, and the heaters in the car at once became more active. There was no heat in the car below, but that was unavoidable. They would try to bring it down to warm levels quickly.

	"Whew, I'm glad we reached the air again, Dick. I didn't tell you sooner, for it wouldn't have done any good, but that battery was about gone! We had something like twenty amp-hours left! I am giving the recharge generator all she will take. We seem to have plenty of power now."

	"I knew the cells were low, but I had no idea they were as low as that! I noticed that the magnet was weakening, but thought it was due to the added air strain. I am going to put the thing into a nose dive and let the glider go down of itself. I know it would land correctly if it had a chance. I am going to follow it, of course, and since we are over the middle of Siberia I think it would be a good idea to start back."

	The trip back was necessarily in the lower levels of the atmosphere, that the glider might be kept reasonably warm. At a height of but two miles, in the turbulent atmosphere, the glider was brought slowly home. It took them nearly twenty hours to go the short distance of twelve thousand miles to San Francisco, the two men taking turns at the controls. The air resistance of the glider forced them to go slowly, they could not average much better than six hundred an hour despite the fact that the speed of either machine alone was over twelve hundred miles an hour.

	At last the great skyscrapers of San Francisco were showing on their horizon, and thousands of private planes started out to meet them. Frantically Arcot warned them away, lest the air blast from their props tear the glider from the magnet. At last, however, the Air Guard was able to force them to a safe distance and clear a lane through one of the lower levels of the city traffic. The great field of the Transcontinental lines was packed with excited men and women, waiting to catch a glimpse of two of the greatest things the country had heard of in the century—Arcot's molecular motion machine and the Air Pirate!

	The landing was made safely in the circle of Air Guardsmen. There was a small hospital plane standing beside it in a moment, and as Arcot's ship released it, and then hung motionless, soundless above it, the people watched it in wonder and excitement. They wanted to see Arcot perform; they clamored to see the wonderful powers of this ship in operation. Air Guardsmen who had witnessed the flying game of tag between these two super-air-machines had told of it through the press and over the radio.

	"Come on, Morey, let's give them a real show, then go home and sleep!"

	"All right, Bill. The invisibility act ought to give them a thrill!"

	There was a sharp click as Morey turned on a switch—then from the crowd below came a mighty roar of amazement! The ship was gone! Gone completely in an instant! They turned to each other in astonished inquiry, and then came another cry of astonishment as it suddenly appeared, hanging in the air a thousand feet above the point of its disappearance! Then it began a series of loops, turns, twists and maneuvers utterly impossible to any other machine. It hung motionless in the air for an instant, then shot up toward the hot, mid-afternoon sun with a speed that left the watchers gasping with astonishment—and continued on its way to New York.

	Two weeks later Arcot had a visitor from the West Coast—a handsome young man of about twenty-eight. Morey was with him at the time. The young visitor looked rather pale, but his six-feet-three made even Morey look to his laurels!

	"Well, I heard you were of fairly good size, Wade, and it is no wonder we had such a whale of a chase catching you!" said Arcot, smiling at him. "Just think, even old earth couldn't throw you down! We had to go out and help bring you in! But, speaking seriously, I hope you have brought your things with you, because if you are willing I think the Transcontinental can afford to let me have a new Lab worker. Dr. Marsh says you will be a great help to me now! After looking over your different pieces of apparatus, both at the Rocky Mountain Perch, as you called it, and in the plane, I am of the opinion that we had better keep all the good rivals in the family, so to speak. That was a neat piece of work on the storage of atomic oxygen! Is it all right for you to get the old head to work so soon?"

	"Dr. Marsh seemed to think so, Dr. Arcot, and I am not in the habit of forcing opportunity to bruise his knuckles! I am with you!" But if the idea for the Atomic Hydrogen storage comes through—"

The End