“A gravity beam!” they ejaculated together in tones varying from incredulity to simple puzzlement. “What's that?”

“Well, it'll take quite a bit of explaining, but I'll drop out the technical part of it… You see, it's like this—You remember old man Einstein, the frizzy-hair Frisian, demonstrated that magnetism and gravity are the same thing down underneath? And that some of the astronomers and physicists have said that both magnetism and light are the same thing? That is, forms of vibration. Well, one of the things I picked up from the lads in this Lassan city was that light, matter, electricity, gravitation, magnetism and the whole works, are the same thing in different forms.

“They've just jumped one step beyond Einstein. Now, they've got a way of producing, or mining, pure light, that is, pure matter in its simplest form. When it's released from pressure it becomes material and raises hell all over the shop. How they get the squeeze on it, I can't say. Anyway, it isn't important.”

“Very interesting lecture—very,” commented Gloria, gravely.

“You pipe down and listen to your betters till they get through,” Sherman went on. “Children should be seen, not heard. But what I've got here is a piece of permalloy. Under certain magnetic conditions it defies gravity. Now if we can screen gravity that way, why can't we concentrate it, too?”

“Why not? Except that nobody ever did it and nobody knows how,” said Ben Ruby.

“Well, here's the catch. We can do anything we want to with gravity if we go about it right. What is it in chemical atoms that has weight? It's the positive charge, isn't it? The nucleus. And it's balanced by the negative charges, the electrons, that revolve around it. Now if we can find a way to pull some of these negative charges loose from a certain number of atoms of a substance, there are going to be a whole lot of positive charges floating around without anything to bite on. And if we can shoot them at something, it's going to have more positive charges than it can stand. And when that happens, the something is going to get awful heavy, and there are going to be exchanges of negative charges among all the positive charges, and things are going to pop.”

“Yes, yes,” said Ben. “But what good does all this do? Give us the real dope on how you're going to do it.”

“Well, with what I picked up from the Lassans, I think I know. They know all about light and mechanics, but they're rotten chemists, and don't realize how good a thing they've got in lots of ways. Now look—if you throw a beam of radiations from a cathode tube into finely divided material you break up some of the atoms. Well, all we have to do is get an extra-powerful cathode tube, break up a lot of atoms, and then deliver the positive charges from them onto whatever we're going for. That would be your gravity beam.”

“How are you going to get radiation powerful enough to split up enough atoms to do you any good?” inquired Ben.

“Easy. Use a radium cathode. The Lassans have the stuff, but never think of using it seriously. They think it's an amusing by-product in their pure light mines, and just play round with it. Nobody ever used it before on earth, because it was too expensive for such foolishness, but with so many less people around, we can get some without too much trouble, I guess.”

“Mmm. Sounds possible,” said Ben. “That is, in theory. I'd like to see it work in practice. How are you going to throw this beam?”

“Cinch. Down a beam of light. Light will conduct sound or radio waves even through a vacuum and this stuff I'm sending isn't so very different. Whatever we hit will act as an amplifier and spread the effect through the whole body.”

“Boy, you want to be careful you don't blow up the earth,” said Murray Lee. “Well, Gloria, I guess we're indicated to go out and dig up some radium. Let's fool them by going before they ask us. There ought to be a supply in some of the hospitals.”

They rose and the other two plunged into an excited and highly technical discussion. When they returned, the workmen had already constructed a black box, not unlike an enormous camera in shape, in the center of the floor. At its back and attached to it, stood a stand fitted with a series of enormous clamps. Ben and Sherman were at a bench, working blowpipes, and shaping the delicate, iridescent glass of a long tube with a bulge at its center.

“Here you are,” said Murray Lee. “I had to row with the Surgeon-General of the Dutch Colonial contingent to get this. He wanted to use it on some tuberculosis experiment. But I convinced him that he wouldn't be worrying about 't. b.' if the Lassans came out of their hole and stood the army on its head. How goes the job?”

“Swell,” said Sherman. “Now you children run along and play. We're busy. We won't be finished with this thing before tomorrow afternoon, if then.”

As a matter of fact it was the next evening before Murray and Gloria were summoned back to the laboratory. The device they had seen was now mounted on a stand of its own, with long ropes of electrical connections running back from it, and had been pushed back to the end of the room. Opposite it was another stand with a two-foot square piece of sheet iron resting on a chair in its center. The lens of the big camera was pointed in that direction.

“Now,” said Sherman, “watch your uncle and see what happens.”


He turned a switch; the tube at the back of the apparatus lit up with a vivid violet glow and a low humming sound filled the room.

“I decided to use powdered lead in the box,” he explained. “It is the heaviest metal there is available, and gives us the largest number of nuclei to project.”

A second switch was thrown in and a beam of light leaped from the camera and struck in the center of the iron sheet, producing merely a mild white illumination.

“Poof!” said Gloria. “That isn't such a much. I could do that with a flashlight.”

“Right you are. I haven't let her go yet. Hold your breath now.”

He bent over, drove a plunger home. For just a second the only visible effect was a slight intensification of the beam of light. Then there was a report like a thunder-clap; a dazzling ball of fire appeared on the stand; a cloud of smoke, and Murray and Gloria found themselves sitting on the floor. The iron plate had completely vanished; so had the chair, all but two of its legs, which, lying in the center of the stand, were burning brightly. The acrid odor of nitrogen dioxide filled the room.

“Golly,” said Ben Ruby, seizing a fire extinguisher from the wall and turning it on the blaze. “That's even more than we expected. Look, it made a hole right through the wall! We'll have to keep that thing tied up.”

“I'll say you will,” said Murray, helping Gloria up. “It's as bad for the guy that's using it as the one at the other end. But seriously, you've got something good there. What happened to the iron plate?”

“Disintegrated. Let's see, where does iron come in the periodic table, Ben? Twenty-six? Then you'll probably find small quantities of all the chemical elements from twenty-five down in that heap of ashes. Phooey, what a rotten smell! That must be the action of the beam on the nitrogen in the air.”

“There's a lot to be worked out in this thing, yet, though,” declared Ben, “and if you're right about the Lassans making a comeback, precious little time in which to work it out. For one thing, we've got to get a searchlight that will throw a narrow pencil of light for a long distance. I don't think those elephant-men are going to let us poke this thing under their noses. And for another we've got to dope out something to keep it in and some way to furnish current for it…”

“Can't you work it from a tank?” asked Murray, “and rig up a friction accumulator to work from the tracks?”

“I can, but I don't like the idea,” Sherman replied. “From the way those Lassans took to our airplanes, I could make a guess that when they come, they're going to come in some kind of flying machine. The dodos are no good in modern war. We'd never catch any kind of an airplane with a tank.”

“How about an airplane for yourselves?”

“Too unsteady and too frail. I want something that will take a few pokes and not fold up.”

“Say, you guys have less ingenuity for a couple of inventors than anyone I ever heard of,” Gloria put in. “Why don't you get one of these Australian rocket-planes and fix it up. It's big enough to hold all your foolishness, and if this thing is half as powerful as it looks, you ought to be able to harness it some way for a power-plant. Then you can plaster your rocket all over with armor. I think—”

Sherman interrupted her by bringing his fist down on the table with a bang that made the glasses rattle.

“You've got it! By the nine gods of Clusium! With the punch this thing gives us used as a rocket, we'd have power enough to fly to the moon if we wanted to. Why a rocket airplane at all? Why not a pure rocket? Let's go.”

It was another week before workmen, even toiling with all the machine-shop facilities of Philadelphia at their disposal, and working day and night, could turn out the machine to Sherman's design, and it was two more before the apparatus was installed. The trial trip was set for the early morning when there would be least chance of atmospheric disturbance.

The Monitor (she had been named for the famous fighting craft with which the American navy ushered in a new age in the history of war) now stood near the center of the flying field at the Philadelphia airport—a long, projectile-like vessel with gleaming metal sides, set with heavy windows, ten feet in diameter and nearly twice as long. At her stern a funnel-like opening led to the interior. This was the exhaust for the power-plant. At her bow the sharp nose was blunted off and its tip was occupied by the lens of a high-powered parabolic searchlight, slightly recessed, and with the discharge tubes for the atomic nuclei arranged around its edge so they would be thrown directly into the light-beam as soon as generated.

As the four approached her she had been placed on the ramp from which she was to start, slanting slightly upward, with a buffer of timber and earth behind it, to take up the enormous recoil her power plant was expected to develop.

“How do you get in?” asked Gloria, walking around the Monitor and discovering no sign of a door.

“Oh, that's a trick I borrowed from our friends the Lassans,” explained Sherman. “Look here.” He led her to a place half way along one side, where two almost imperceptible holes marred the shining brightness of the new vessel's sides. “Stick your fingers in.”


She did as directed, pressed, and a wide door in the side of the projectile swung open. “Bright thought. No handles to break off.”

They stepped in, bending their heads to avoid the low ceiling.

“She isn't as roomy or comfortable or as heavily armored as the one I mean to build later,” explained Sherman, “but this is only an experimental craft, built in a hurry, so I had to take what I could get… Now here, Murray you sit here. Your job is going to be to mind the gravity beam that furnishes us our power. Every time you get the signal from me, you throw this power switch. That will turn on all three switches at the stern, and shoot the gravity beam out for the exhaust… You see, we can't expect to keep up a steady stream of explosions with this kind of a machine. We wouldn't be able to control it. We'll travel in a series of short hops through the air, soaring between hops, like a glider.”

“How are you going to do any soaring without wings?” asked Murray.

“We have wings. They fold into the body at the back. I've made them automatic. When the power switch is thrown the wings fold in; after the explosion they come out automatically unless we disconnect them. If we want to really go fast, we'll disconnect them and go through the air like a projectile.”

“Oh, I see. Will the windows stand the gaff?”

“I hope to tell you they will. I had them made of fused quartz, with an outer plating of leaded glass, just in case the Lassans try to get fresh with that light-ray of theirs.

“Now, Gloria, you sit here. You're the best shot in the crowd, and it's going to be your job to run that searchlight in the prow. As soon as you pick up anything with it, Ben will throw his switch, and whatever is at the end of it will get a dose of pure protons. We'll have to do a good deal of our aiming by turning the ship itself. I made the searchlight as flexible as I could, but I couldn't get a great deal of turn to it on account of the necessity of getting the nuclei into the light beam.”

“By the way,” asked Murray. “Won't this pure light armor of the Lassans knock your beam for a row of ashcans?”

“I should say not! If they use it, we've got 'em. That stuff has weight and the minute this beam of ours hits it, it will intensify the effect, and no matter how much pressure they have on it, it will blow up all over the place… All set? Let's go. Throw in your switch, Murray.”

Murray did as directed. There was a humming sound and the tiny beam of light leaped across the rear end of the ship and out the exhaust. Across it fell a thin powder of iron filings—the material that was to be decomposed to furnish the power.

Bang! With a roar, the Monitor leaped forward, throwing all of them back into their heavily padded seats, then dipped and soared as the wings came into play. The passengers glanced through the windows. Beneath them the outskirts of Philadelphia were already speeding by.

“Say,” said Ben, “this is some bus. We must be making five hundred miles an hour.”

“Sure,” said Sherman. “We could do over seven hundred as a pure projectile, but we can't use that much speed and keep our maneuvering power.”