The projector had been stopped exactly on the first frame, showing the invisibility of the safe. Then Arcot backed it up.
"True, Dad," he said, "but pay special attention to this next frame."
Again there appeared a picture of the room, the window beyond, the mail clerk asleep at his desk, everything as before, except that where the safe had been, _there was a shadowy, half visible safe_, the metal glowing brightly. 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 plane.
"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 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 entered.
"Morey," asked Fuller, "what did you learn about that gas the pirate was using? I remember Arcot said he would have some samples to a.n.a.lyze."
"As to the gas, d.i.c.k 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 d.i.c.k thinks that this may account in part for its ability to suspend animation. However, since it was impossible to determine the molecular weight, he could not say what the gas was, save that the empirical formula was C_{62}TH H_{39}O_{27}N_{5}. It broke down at a temperature of only 89 centigrade. The gases left consisted largely of methane, nitrogen, and methyl ether. d.i.c.k is still in the dark as to what the gas is." He paused, then exclaimed: "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. Morey had disappeared!
"Why--why where--ohhh! Quick work, d.i.c.k!" The senior Arcot began laughing heartily, and as his astonished and curious companions looked toward him, he stopped and called out, "Come on, d.i.c.k! We want to see you now. And tell us how it"s 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 extending from it 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"ve been 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"s a bit heavy, so if you"ll clear a s.p.a.ce, I"ll 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, and I had no time to rig up a little mechanism like the one 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, it hasn"t been used. 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, existing apparatus 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. Our friend the pirate has developed this thing to a point were he could use it. You can see that invisibility, while interesting, and a good thing for a stage and television entertainment, 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. His gas, too, made the thing attractive. The two together made a perfect combination for criminal operations.
"The whole thing looks to me to be the work of a slightly unbalanced mind. He is not violently insane; probably just has this one particular obsession. His scientific b.u.mp 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? You"ll remember his careful instructions as to how to revive the people!
"He has developed this machine for invisibility, and naturally he can fly in and out of the air guard, without their knowing he"s there, provided their microphonic detectors don"t locate him. I believe he uses some form of glider. He can"t use an internal combustion engine, for the explosions in the cylinders would be as visible as though the cylinders were made of clear quartz. He cannot have an electric motor, for the storage cells would weigh too much. Furthermore, if he were using any sort of prop, or a jet engine, the noise would give him away. If he used a glider, the noise of the big plane 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 pa.s.sed beneath. He has a very simple system of anchoring the thing, as I discovered to my sorrow. It"s a powerful electro-magnet which he turns 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 it was very highly magnetized--I could pick up needles with the balance wheel. I demagnetized it; now it runs all right.
"But to get back, he anchors his ship, then, leaving it invisible, he goes to the air lock, and enters. He wears a high alt.i.tude 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 grains of gas give one hundred thousand calories. Oxygen has not been prepared in any commercial quant.i.ty 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. The center flame probably develops a temperature of some 4000 centigrade, and will naturally make that tungsten alloy run like water.
"As to the 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 pa.s.s through readily. You know that metals transmit light for short distances, but in order that the light pa.s.s, 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 pa.s.s 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 a wavelength that alone would tend to produce invisibility. But in this case it will make me visible. I"m going to stand right here, and Bob 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 and knowing that they were looking through his body. It gave them 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, Bob, 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 too.
"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 phenomena 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 didn"t experiment with it beyond the laboratory stunt stage. I published some of the theory in the Journal of the International Physical Society--and I wouldn"t be surprised to learn that the pirate based his discovery on my report.
"I am still working on a somewhat different piece of apparatus that I believe we will find very relevant to this business. I"ll 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 of design if this works out, as I hope it will."
"I"ll certainly make every effort to be here, Arcot," Fuller a.s.sured him.
"I can promise you a tough problem as well as an interesting one." Arcot smiled. "If the thing works, as I expect it to, you"ll have a job that will certainly be a feather for your cap. Also it will be a change."
"Well, with that inducement, I"ll 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"ve done some high-alt.i.tude gliding already. The distance record took someone across the Atlantic in 2009, didn"t it? But it seems 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 probably takes him half a day to get there. And it would be easy for a plane to pa.s.s 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 one of the new hundred horsepower jobs would weigh only about fifty pounds. 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 men got together for dinner, and there was considerable speculation as to the nature of the discovery that Arcot was going to announce, for even his father had no knowledge of what it was. 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, 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," Arcot junior said quietly, "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 horsepower. 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 connectors. 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"ll guarantee results--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 faint hum from the coil; then it was gone. There seemed to be no other result. He rotated it a bit more; a slight draught sprang up within the room. He waited, but when nothing more startling occurred, he gave the rheostat a sharp turn. This time there was absolutely no doubt as to the result. 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 came suddenly alive and whirled madly before the blast of air that had suddenly leaped out. Dr. Arcot was forced back as by a giant hand; in his backward motion his hand was lifted from the relay switch, and with a thud the circuit opened. In an instant the roar of sound was cut off, and only a soft whisper of air told of the furious blast that had been there a moment before.
The astonished physicist came forward and looked at the device 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 twinkle in his eye.