Murfree saw. He saw much more than Bud Gregory could tell him. He envisioned a quarter-mile circle of wire, built in a remote mountain valley. It made a horn-shaped —cone-shaped—barrier reaching down into the earth. Nothing could pass through that barrier, not even neutrons.
There is some slight radio-activity everywhere. Even rocks possess it. It is the cause of the internal heat of the earth. Perhaps the unknown man had come upon indications of uranium ore underground in that valley, perhaps not. But, surrounded by a shield through which no neutron could escape, any mass of material on earth would become an atomic pile!
A SINGLE molecule of uranium in any mass of rock will sooner or later disintegrate, giving off high-speed neutrons. Normally they travel indefinitely and are harmless. Some go up into the air and may ionize a single molecule. Some may find a fissionable atom and disrupt it.
But by far the greater number are simply lost. Because they can escape. Within a barrier from which they cannot escape, they would bounce backward and forward until, within even a limited mass of matter, they did disrupt another atom. Neutrons from that disrupted atom would then go on and on!
An ordinary atomic pile must be of a certain minimum size because it loses so many neutrons from its outer surface that no chain-reaction can maintain itself. As the size of the pile increases the number that does not escape increases faster than the number that does. There is a size where enough strike fissionable atoms before escaping to maintain the reaction.
When as many are freed as escape the pile, a chain reaction sustains itself. But when none can escape, there is no minimum size. There is no minimum purity of materials. Prevent neutrons from escaping and anything at all, of any size, becomes an atomic pile.
Murfree passed over a third dollar bill. "Now I'm paying you to listen to me," he said evenly. "That man used your outfit and made a circular block for neutrons a quarter-mile across with the horn pointed down. Maybe a million, maybe five million tons of rock were inside it. Maybe there was some uranium in it too. None of the neutrons could escape. Each one bounced back and forth until it broke another atom. That made more neutrons bounce back and forth and break other atoms. You knew that would happen. You knew even a little pile would make him sick. But he made a monstrous one! It didn't make him sick. It killed him.
"Perhaps he intended to run it a while and then shut it off. It would have created enough radioactive isotopes by its normal working to make him a millionaire many times over. But he didn't turn it off in time! Because it killed him! And so the pile kept on working!
"Back in the mountains it's working now. There's hot air rising from it, and every breath of it is deadly poison! It goes up high and the winds spread it and presently it comes down to the ground again and kills. He didn't turn it off!"
Bud Gregory gaped at him. It was clear that he had never thought of such a thing. So much more than a genius that there is no word for it, he was like a child or a savage in that he could not think ahead. But he understood now. The unnameable intuition which had carried him to the achievement of a miracle had not told him the consequences of the miracle. But as Murfree pointed them out he saw.
"M-my gosh!" said Bud Gregory. He looked enormously concerned.
"Nobody can live to get to it to turn it off," said Murfree, grimly. "Maybe a plane can drop a bomb that will blast it. But it'll be weeks before I can make myself believed.
Meanwhile there's poison being poured into the air. People are dying right now.
"For five miles around that thing you made, there's not even a blade of grass alive. The people in the cabins for ten miles around are dying and don't know why. And that horn-shaped mass of ore and earth inside your field is full of more flying neutrons than any atom pile ever was.
"Suppose we turn that shield off with a bomb and all those free neutrons are turned loose at once! How far away will they kill every living thing? Fifty miles? A hundred miles?"
Bud Gregory swallowed. He undoubtedly understood more clearly than Murfree himself, now that it was pointed out to him.
"M-my gosh!" he said again. "I—uh—I didn't meant nothin' like that!"
Murfree handed him a fourth dollar bill with an indescribable sensation of irony. "Now tell me how to turn it off without killing everybody all the way to here!" he commanded evenly. "If it kills me to do it that's all right. But if you don't tell me how to stop the thing I'm going to kill you, you know. Here and now."
He didn't raise his voice. He didn't realize that he was threatening. It simply seemed necessary. If Bud Gregory could doom a continent or a world and not be able to stop what he had created, he was too dangerous to be allowed to live.
But Bud Gregory spoke unhappily.
"I didn't mean nothin' like that! I just meant to make that fella sick as a dog. I figured he might make a little horn an' sleep in it when he camped. He'd be plenty sick by mornin'. But the dumb fool—" Then he knitted his brows. "I'll figure out something. I gotta knack for that kinda thing."
CHAPTER V
... Who Wasn't There
JUST three days later, Murfree was back at the high hill-crest which was actually a pass between mountains. A steady wind blew from behind him. All about him the world was dead. Nothing lived. Nothing! He didn't carry the counter, now. There was no point in it.
He carried, instead, a clumsy contrivance set up in a wooden box in which canned tomatoes had once reached the village of Brandon.
Bud Gregory walked with him, anxiously holding before him a loop of wire which he said would stop the neutrons for his own protection. Bud Gregory had actually sat up at night to make the outfit for his own protection and the mass of tangled wiring Murfree carried.
They reached a spot where they could look into the valley beyond. It was literally a valley of death. There was nothing alive in it. Not one blade of grass, not one shrub, not one bird or insect, not even a bacterium. Everything was dead.
And a swirling, humming column of heated air rose skyward, snatching up deadly dust from a quarter-mile patch of earth that was quite red-hot, now. Every grain of that dust was the most deadly stuff known to men.
Bud Gregory looked. He was pale. He had come through miles of desolation. He had seen the silent cabins of the mountain-folk and the shriveled crops that they had planted. He knew that he had made the thing which had killed them. But now, looking down at the carbonized half-cabin and the heap of huddled garments in it which had been a man, he muttered defensively.
"That fella played heck! I told him it was dang'rous!"
He propped up his loop of wire so that it still protected him. Murfree silently unloaded himself. Bud Gregory made a final assembly. There were a few—a very few—radio tubes. Murfree had traced every lead in the complicated wiring, and he could not even begin to understand it.
By all modern knowledge of electronics, it would do nothing whatever. The tubes would light and current would flow and nothing would happen—according to modern knowledge of such things. But Bud Gregory had labored over it and risked his life to bring it here.
He was untutored and almost illiterate, while Murfree had spent years in the study of just such science as this should represent. So Murfree helped as a naked savage might help to set up a radio-beam, in absolute ignorance of even its basic principles.
"Like I told you," said Bud Gregory in a troubled voice, "this new outfit is like that there thing that makes that—uh—pile. Only this don't make a hollow horn. This here is solid. It won't only stop them—uh—neutrons from goin' through a place. It'll stop 'em dead in their tracks, right where they are when it hits. It's gonna make a lot of heat."