Ranger Boys in Space

The boy behind the wheel of the ancient car leaned out as he called, as though to make his voice travel farther. He didn't really need to; not only were his lungs powerful enough for any demand likely to be put on them, but the car itself had nothing to interfere with his call. It had once been a convertible, but the top had been removed long before the machine came into Bart Ranger's possession. He claimed that it was the oldest powered vehicle still on any American road, and none of his friends ever argued the point.

Sometimes an unsuspecting garageman, listening to the nearly silent motor, claimed that Bart was cheating and had put an old body on a modern chassis, but the mechanic was wrong. The motor's condition was the result of many hours of work on the part of Bart, his younger brother, and Peter Ashburn.

"Come on, Pete! He'll be taking a taxi if we don't get going!"

"Keep your shoes on!" The voice floated from an upstairs window of the house, and the occupants of the car relaxed. Peter appeared at the door a moment later and walked toward them. Neither Bart nor his brother expected him to run; Peter Ashburn very seldom hurried on dry land, insisting that he needed his energy for swimming. He got into the car and Bart immediately swung out of the drive, turned right, and found his place in the Washington-bound traffic. Rhode Island Avenue was not too crowded yet, but he knew what it would be like farther in.

The other two paid little attention to the driving problem. They were looking forward to meeting Jim Bowen, who had been gone for several months this time.

"It's too bad that Uncle Jim can't get home a little oftener, when he's only as far away as Niagara," remarked Dart (he had been named for his uncle, but only his schoolteachers ever remembered that fact) .

"Are you trying to sound innocent just because we're in public?" asked Peter. "You know as well as I do what he's been doing, and why he's really been a lot farther off than Niagara most of the time. Do you think there's someone in the back seat listening in?"

Dart admitted that it was probably safe, but added, "You know Uncle Jim said to keep quiet about this business. He said he'd told us because he trusted us, and if he'll let you in on something like that when you're not even his nephew, I should think you'd be pretty careful about talking."

"You're right," admitted Peter, "but you know as well as I do that I haven't said a word where anyone could hear us. Who was it only a couple of weeks ago who was wishing out loud that he could go along with his Uncle Jim? It was you, and you were doing it in my yard, where there was a lot better chance of being heard than there is here."

"Why argue about it?" Bart cut in without taking his eyes from the road. "Uncle Jim knows he can trust us; we all know there was no one listening that day in your yard because there was no place within earshot where anyone could have hidden, and we've all wished out loud at different times that we could be with him. Pete's asking at school why there wasn't any course being given in astronomy, for that matter—"

"—would have been a giveaway if everybody didn't know I was a bookworm anyway," finished Peter. "Better change the subject or you'll be right into the argument with Dart and me."

"All right. How long do you think Uncle Jim will be home this time?"

"Not long, unless things have changed." Dart's remark was made in a gloomy tone.

"Maybe they have." Bart sounded more cheerful. `Remember, before he went he said, 'This time ought to clear things up.' "

"You mean they might get up and stay up this time?" asked Peter. "Why would that let him out? I should think that that would be the time he'd really get to work; he's a geographer, not an engineer."

"I only know what he said. Anyway, if they've really finished the job, maybe he'll be able to tell us a good deal more. Besides, we're older than when we first heard about it, and maybe we'd stand a chance to get in on it ourselves."

"I don't know about that, Dart," remarked Peter. "With Bart and me only sixteen and you a year younger, I'm afraid there aren't very many people who are going to assume we can do a man's job at anything."

"But when it's something no one has done before—maybe we could talk our way in." Peter shook his head doubtfully, and even Dart would have admitted without much pressure that his remark was more wish than hope.

Before any more could be said on the subject a whine sounded above and behind the car. Peter and Dart looked up.

"Is that the plane?" asked Bart. Peter shook his head.

"No. Wrong course, wrong kind, and too early. This one's in a turn—must have come from the south and be cutting around to land on the southwest strip. We'll make it all right." Bart nodded and glanced upward to make sure as the sound of turbines drew ahead of them.

For some minutes there was silence while the car hummed deeper into the town. All the boys were thinking about James' Bowen, the "Uncle Jim" of the Rangers. He was a widely known man; he had accompanied exploring expeditions to Antarctica and the Amazon Valley, and was one of the few to have reached the summits of both Everest and K2 on foot. He had taken over the guardianship of Bart and Dart when their parents had been killed ten years before. His nephews had grown up with the hope of going with him on his regular work when they were old enough.

Peter also thought of him as "Uncle Jim," though he himself was not related either to Bowen or to the Ranger boys. He had met them three years before when his own guardians had moved to Washington, and a friendship had grown up between them, though Peter Ashburn was very different from the brothers. He was Bart's age, but that was all. The Rangers were athletes, Dart's chief ambition being to beat Bart consistently at any sport he could manage. He came closest in tennis and track—his nickname did not come entirely from its resemblance to his brother's—but never quite made the grade. Peter, on the other hand, cared little for any sport except swimming, and, as he had said, had something of a reputation as a bookworm. His friends could slightly understand his liking physics and chemistry, his claim to enjoy mathematics was viewed with some suspicion.

In spite of this difference, he got on remarkably well with the brothers. Peter never tried to account for it; he liked Bart, Dart, and their uncle, and all three liked him. He was as eager as the Rangers to reach the airport in time, and was relieved when the car swung out onto the lower deck of the Fourteenth Street bridge, two minutes from the airport parking space, with no sign of the airliner from the northwest.

They crossed the river, swung off onto the ramp feeding the airport, left the car, and were climbing to the concourse when Dart saw the incoming liner. It was just a speck in the clear sky, but none of them had any doubt of its identity.

By the time they had reached the rail overlooking the unloading ramp, the big machine was close enough for details to be seen. It was coming straight in, its landing gear already down, the six turbines which drove its huge propellers throttled back so that they could barely be heard. The boys watched closely as it eased downward; they all knew something of flying from their schoolwork, though they had never handled planes themselves.

It was hard to tell just when the already spinning wheels touched the runway, but the fact that they had done so was heralded by the sudden rise in the sound of the turbines as the pilots reversed pitch to slow the great aircraft down. It rolled majestically past, a quarter of a mile from the concourse, still losing speed; in another half mile it had come to a halt and swung clear of the runway. Slowly it ambled back, reminding Bart of a rather fussy, well-dressed old man picking his way through a crowd of boys with snowballs as it passed the other planes parked along the ramp. It came as close as possible to the concourse, turned around so that one wing tip passed only a dozen yards from the boys, halted, and let its great propellers swing to a stop. Three doors along the fuselage opened out and down to form ramps, and the passengers began to stream toward the terminal buildings.

Peter took his attention from the heat-blur around the jet exhausts as Bart called his name.

"Pete! You take the forward door; I'll handle the middle one and Dart the tail. Yell if you see Uncle Jim." Ashburn nodded and tried to obey, but it was no easy job. All the doors were wide enough to let several people out abreast, and the liner must have had over two hundred passengers to discharge. It was a local, terminating at Washington, so no one would be staying aboard. He strained his eyes until the stream of people thinned to a trickle and finally ceased; then he looked at the other doors. The rear cabin seemed also to have emptied, but a few people were still emerging from the center one. After a few moments this flow ceased also, and the boys looked blankly at each other for a moment.

"He must have been in the front," Dart said at length. "I suppose Pete was watching the exhausts cool, or something like that."

"I was watching the door," Ashburn replied. "I'm as sure he didn't come out mine as you are about yours. Could he have been up in the cockpit?"

"Illegal, even for Uncle Jim," remarked. Bart. "No, we must have missed him. He'll probably be picking up luggage down below; if we don't catch him there, we can have him paged—if he doesn't beat us to it." He turned away from the railing.

Peter was the last to leave; it was he who took a final look at the great plane behind them and saw something which made him stop in his tracks, stare, and then call to the others with all the power of his lungs.

"Bart! Dart! Here, quick!" The others whirled and leaped back to his side.

The airliner had not quite emptied itself. The compartment just back of the cockpit was served by a small elevator, used to carry aboard such items as test apparatus or food, and this had started down. It had been hidden at first by one of the landing-gear doors, but now the boys could see what it carried.

There were three people on the small platform. One was either the pilot or some other airline employee, judging by his uniform, and another a tall, dark-haired man dressed in clothes that seemed designed for hard work. Both these people were giving their attention to the third man, who was seated between them in a wheel chair.

It was not possible to tell at first glance what was wrong with him. He was not covered by a blanket, but in spite of this there was no sign of casts, bandages, or any other of the usual reasons why a man may not be able to walk on his own feet. His face looked thin, though he was a little too far away for the boys to be sure. At this distance he closely resembled the workman standing by his wheel chair.

For just a moment the eyes of the boys rested on the man in work clothes, whose build and coloration were not too different from those of James Bowen; then, almost simultaneously, they realized their error. In spite of the loss of weight, the anxious expression which was now visible, and the evident helplessness, the man in the wheel chair was Uncle Jim.

THE FAILURE

IT WAS fortunate that most of the other people had already left the concourse, for the boys broke all records and several regulations going down the stairs. At the bottom they turned toward the ramp without slackening their pace. A guard at one of the gates started to intercept them, then seemed to realize the situation; he stepped back out of the way, and the boys went by scarcely noticing him.

The elevator had reached the ground and the chair was being wheeled toward the gate when the boys reached it—Peter well behind the others, by this time.

"Uncle Jim! What happened? Was there an accident? Did it—?" The last question of Bart's was interrupted by a sharp nudge from his younger brother.

James Bowen looked up, and tried to smile. It took an effort that the boys could see easily, and which shocked and startled them almost as much as had the original sight of their uncle in a wheel chair. The expression underlying that forced smile was one they would have called fear, had it been on anyone else's face, but none of them could imagine James Bowen's being afraid. He was thin, as they had already seen—fully twenty-five pounds lighter than when he had left them, and Peter noticed that his hands were gripping the arms of the chair so hard that the knuckles were white. He did not release that grip even to shake hands, and Peter wondered.

"Hello, boys." Bowen's voice was nearly normal, at least. "It's good to see you again. No, it's not exactly an accident; it's something we were a little afraid of all along. I'm—"

"Then you're sick?" Dart cut in. "Will it last long? Was it radiation, maybe?" Bart returned the nudge, to silence him.

"No, not radiation. I'll tell you all about it when we get home."

"Then you can come home? You're not hospitalized?"

"No, Pete. I'll be with you very shortly."

"But we have the car here; aren't you coming with us? If you don't need to go to a hospital, what else is keeping you?"

"Well—you still have the same car?"

"Of course."

"Then I think I'll go in the ambulance I see they have waiting. It's nothing to do with your driving; I'll explain that, too, when we get home. You go along; I'll meet you there."

Bart looked with troubled eyes at his uncle for a long moment; then without another word he turned and went back toward the parking lot. The other boys followed silently, and the old car was humming back across the Potomac before anyone spoke. When the ambulance passed them there, Peter, usually the quietest of the trio, said, "Step on it, Bart." Bart would normally have made some answer designed to "keep the bookworm from getting above himself," but this time he simply nodded, and by some trick did manage to keep the ambulance in sight most of the way home.

He pulled into the drive behind it while Uncle Jim was still being helped up the front steps. The boys watched, not daring to help until they had some idea of what was wrong. Bowen seemed strong enough, but he had to feel carefully for each step with his foot before he put weight on it, and although it was obvious that he could see, the men on each side seemed to be guiding him. The boys followed the group through the door and waited silently while the wheel chair was brought in and the patient settled in it. Mrs. Lynn, the housekeeper, for once was too shocked to speak.

"Thanks, Doctor." Bowen addressed these words to the man in work clothes, rather to the boys' surprise. The doctor nodded.

"All right, Mr. Bowen. As you know, we can't tell just how long this will last; I'm staying in town and will call at least once a day. If any change should occur when I'm not here, please call. You know about keeping a running report on your condition."

"Right. I'll do that as well as I can myself, and the boys here will supplement my observations from outside."

"You're going to tell them the story?"

"All of it." The doctor shrugged.

"That's your affair, and of course you know them better than I do." Bowen hastily presented the boys to Dr. Kellner, who acknowledged the introduction, remarked that he had better check in at Reed, and left. The boys scarcely noticed his departure, except for the fact that they were now alone with Bowen; without waiting for an invitation they settled down in various parts of the room to hear what he had to say.

"I'm sorry that I came back this way, boys; it mist have been quite a jolt to you. The whole thing is a long story, and I don't quite know where to start. You know what we were doing. People have been arguing for years about whether it was worth while to spend the time and money getting a rocket out of the atmosphere and into a permanent path around the earth. Time and time again the engineers came up with plans: always very, very complicated and very, very expensive, and somehow the project never really got under way—whichever service happened to be concerned at the time couldn't get the money needed. Then, as I told you, something happened which cut down the complication and the risk to almost nothing. I couldn't tell you what it was at the time, since it was completely secret, I did tell you that we had the satellite project under way, that the station was being built, and that we hoped to get it up before long.

"It was, and is. Three weeks ago it was launched, and is now circling the earth between three and four thousand miles up."

"Then you've succeeded!" Dart leaped to his feet. "You've been in space!" He sobered down a little. "I suppose all this is still secret, though."

James Bowen was silent for a long moment.

"It will be no secret after tonight," he said at last, "and it's no success, from our point of view."

"What?"

"We have failed. I can tell you more now, since, as I said, the news is being released anyway.

"The thing which seemed to remove all difficulties was an entirely new rocket. You must have learned in school that the problem with early rockets was the terrific amount of fuel they wasted in building up speed. It was known that the faster you could squirt gas out of the rocket's tail, the less fuel you needed to get to a particular speed; so they did their best to make more and more powerful fuels, since it was the energy in the fuel which had the most to say as to how fast the gas went out.

"About a year and a half ago, a completely new motor was built. It is still a rocket, but it uses water as the 'gas' and shoots it out at many thousands of miles a second—so fast that a ship weighing as much as an ordinary jet fighter and carrying the same amount of fuel could go anywhere in the solar system, using power all the way, instead of coasting. It was very wasteful of energy—maybe you've had enough math to see why, Pete—but we could afford the energy; it was powered by the same reaction that makes the sun go—the so-called Phoenix reaction, something like that in the old H-bombs, I guess. The important thing was that a ship could now carry all the fuel it was ever likely to need; we began to see ourselves running around the whole solar system in the next couple of years. In fact, there was an argument for a while that we shouldn't try to build the satellite station—there would be no use for it, since any ship could take off from the earth and still have fuel enough to go anywhere it wanted. We finally decided to build it, though, since it would have a lot of uses besides a fueling station. That much you knew."

"And it's done and up? How can you say you failed, then?"

"It's finished, and in its orbit, and there is a crew aboard. Twenty years ago, anyone would have said that we had done ninety percent of the work toward conquering the inner planets.

"However, there's a catch. Pete, when you first started diving, how did it feel between the time you left the board and the time you hit the water?"

"Well—I don't know. Or at least, I don't remember. I don't think it bothered me much."

"Well, then, how about elevators—just as you start down, or just as you stop on the way up?"

"It's not too bad. I used to get sort of queasy in the stomach, but I hardly notice it now."

"Do you think you'd notice it if it didn't stop?"

"What do you mean?"

"The elevator feeling occurs when you accelerate downward, so that your feet don't press the floor so hard, your insides don't press down on each other so hard, and the fluid in your middle ear which controls your sense of balance doesn't stay so firmly in the bottom of its tubes. Since you never can accelerate for more than a few seconds in a downward direction while you're on the earth, you never suffer the sensation for long. In a rocket, though, you'll feel it any time you're using power different from the amount you need to accelerate at falling-body rate, and if your power is off—" He shook his head, and the expression on his face grew sharper.

"If it's off, I should think you'd have no weight at all," Peter remarked.

"That's right."

"But why should that bother you? I should think it would be fun; you could float around without—" Bowen, falling from his usual standards of courtesy, interrupted.

"Don't say that! You don't float; you fall! And believe me there's a difference! With no weight at all, nothing keeps the fluid in your middle ear at the bottom of its semicircular canals; it spreads out and covers the whole inside of them. That means your brain gets signals that you're right side up, upside down, and lying on your stomach, back, and both sides all at once. The closest thing you get to it on Earth or any planet of decent size is when you spin yourself around rapidly for a while and then stop suddenly, so that the liquid sloshes around inside; then your sense of balance tells you that one way is up and your eyes tell you something different. The good thing is that it only lasts a short time."

"Spinning makes me dizzy," remarked Dart.

"And what I've been describing is just that—dizziness," replied his uncle. "You get dizzy; you feel as though you were falling but you don't know which way is down, since there isn't any 'down.' For a while you keep yourself under control, telling yourself that it's all right and you're not going to run into anything and that you don't really care which is down—that it's no worse than learning to fly an airplane on instruments, when you have to disregard your sense of balance too; but sooner or later your feelings win out over your mind. If it doesn't happen while you're on duty, it does later—for example, while you're waking up from sleep and don't quite know yet what is going on around you."

"I think I see," Peter said after a moment's silence.

"I should think you could get used to it, though, after a while; and didn't you say that there was a crew aboard that satellite station? That can't be using power, and must be weightless; how do they stand it? Did you get them used to it by easy stages?"

"We thought that might be possible, at first," Bowen replied. "We knew that weightlessness wouldn't be comfortable, of course, and expected that it would take a good deal of getting used to; so we designed the station to spin. Centrifugal force in the outer portions was to act as artificial gravity and make the place more or less comfortable, while the parts near the center could be used for weightless practice."

"And it didn't work?"

"It didn't. Every soul on board got deathly sick while we were working into the position and velocity needed for the orbit, while weight was changing constantly and 'down' altering its direction all the time; when we were finally set up, and power went off altogether, only one man was able to control himself enough to get the thing spinning. About half of the men failed to get their sense of balance back for the best part of a week; when they did, we started experimenting as you suggested, Pete, to see whether we could get used to it.

"All I can say is that we tried, in every way anyone could think of, and we failed. Some of them are trying yet—I suspect that they offered to stay because they couldn't face the thought of the trip back. I lost my sense of balance during one of the experiments, but I had to come back no matter how I felt. That's why I didn't ride back with you; I could see the sky from your car, and it's hard to look at if you don't know whether it's up or down."

"Is this permanent?" asked Bart in alarm. He had visions of his uncle spending his life in a wheel chair. "How can I tell? Nothing like this has ever happened to anyone before. At least, I'm getting so that I can stand it a little better, and can sleep for a few minutes every now and then. It was pretty bad at first, I must admit, and I still don't like to think about the cause. That's why I was so rude a little while ago, Pete, when you talked about the joys of weightless floating; believe me, it's no joy!"

"Then they're giving up on the whole business of space travel? You said that secrecy was being ended tonight," Peter said.

"I'm afraid they are. It seems logical to me, though I don't like it any better than you do. What we're facing is the fact that man spends a lifetime training his mind and nervous system to link together the messages from his muscles, his eyes, and his semicircular canals; now he faces a situation where those messages disagree with each other. It's no wonder his mind quits under the strain. I'm afraid, Pete, that we're not going to walk around on the deserts of Mars—ever."

THE WIRE

FOR several minutes the room was silent. Although the boys had been really too sensible to expect to accompany their uncle into space in the near future, they had been looking forward to exploring the planets when they were older; Uncle Jim's flat statement that this could never be done was a shock. Being boys, they found it hard to believe. Bart was the first to give voice to this feeling.

"I can't see it, Uncle Jim. You say that you've been working on this particular problem only three weeks and have already given it up? That's not like you, and it's not like the picture I've always had of scientists. You've told us time and again how it has taken years to solve some of the problems Old Lady Nature has set up, and lots of others aren't solved yet—but they aren't giving up on them."

Bowen flushed slightly.

"I suppose it would seem that way to you. However, I can assure you that a number of pretty brilliant people have been considering this question since it came up, and they haven't even been able to think of a line of attack on the problem. That's a little different from the usual situation, where the investigator at least knows where he's heading.

"Still, you're partly right. The actual reason for publicizing the whole thing is to get more ideas. We all admit that there may be an answer, but we have no idea of what it will be like. What I said is true; a person spends his whole life in oufitting himself for space, and practically has to throw his brain out of gear in order to be able to stand weightlessness. Since he's not much use without a brain—" Bowen shrugged.

Bart nodded slowly.

"I suppose you must be right, though it seems to me that there must be ways—how about some drug that numbs your ears, so that you don't get the dizzy sensation?"

"I'm already in that condition, with the result that I not only can't fly but can't walk."

"It seems to me I've heard of folks with some kind of deafness which interfered with their ear canals, but they were able to get along all right."

"Yes, we thought of that before the take-off, and had two of them on the crew. They're both still up there; neither wants to face weightlessness again. Apparently they depend more than most people on muscle sense—the thing that tells you whether your leg is straight or bent and whether the head that has your normal sense of balance is sitting straight on your neck."

Bart was silent, and his brother took up the questioning.

"How do they know that anyone who gets an idea from this new publicity won't keep it to himself and use it for his own ends? As I understood it, that was the reason for the original secrecy."

"That was most of it. The news accounts tonight are not going to carry complete specifications for the Phoenix motor, though, and ideas of the sort we want won't be much use by themselves. I think there's a pretty good chance, actually, that we'll get something."

Dart had been frowning through a good deal of this conversation. Now he spoke up.

"Since this whole thing was never a military proposition, just why was all the secrecy being observed, anyway? You told us not to tell anyone, and somehow we always thought about how long we'd spend in jail if we talked; actually, would there have been any law broken if we had?"

"No; but your respected uncle would have been out of a job. The Geographic Institute did make agreements with several governments, according to which we were to get to the planets first. It was for just one reason, really; if private individuals or government-sponsored expeditions make the first landings, there'll be a lot of legal fuss about who owns the planets, because no laws have been really worked out on the matter. If an international outfit like Geographic gets there first, at least there won't be anyone claiming the moon or Mars by right of first landing or something. Actually, the whole thing is not too important, the average man would say, but it might save a lot of argument later, and that was the reason for the agreement."

"But do they think anybody else is actually trying to get out into space? I never thought of anyone's trying to claim the moon just because he landed there first. It sounds silly."

"Not so silly when you think about the arguments over who owned the Americas, back in the sixteenth century," Bowen pointed out. "Anyway, that was the reason for it all; the fact that no spies seem to have kidnapped any of the Institute group to make them tell about the project doesn't make the whole idea senseless. We are still, as I say, keeping the details of the Phoenix motor as secret as possible, so—" he grinned —"if you see any spies around, better let me know." The boys realized he did not mean this literally, and probably did not believe for an instant that there would actually be an attempt to spy on them, but one of them, at least, took the matter seriously. It was just as well he did.

The question bee broke up as Mrs. Lynn called from the kitchen that supper was nearly ready. It was taken for granted that Peter would stay, as he normally did when Bowen was home. Bart got up and began pacing the floor in thought; Dart went off on some project of his own. No ideas had emerged from any of them by the time the housekeeper called out that the food was ready.

Bart pushed the wheel chair into the dining room, while Peter brought the hot dishes from the cooker, and the two boys sat down beside Bowen.

"Where's Dart?" asked Peter as he reached for his napkin. "He must have heard." The others listened for a moment, but heard no sound of approaching footsteps.

"He's interested in something," sighed Bart. "Goodness knows it's not the first time. Shall we hunt him up, Uncle Jim, or let him remember for himself?"

"I'm a little curious to know what could be holding his attention at this point," replied Bowen. "I can wait, if you want to collect him." The two boys shrugged and rose from the table in unison.

"You try up, and I'll go down, Pete." They started for the door, but before they reached it they were stopped by the sound of hasty footsteps in the hall outside. An instant later the missing member of the group plunged into the room and skidded to a halt beside his uncle's wheel chair, panting heavily.

"Uncle Jim! I thought you were kidding about that spy business!"

"I'm afraid I was, Dart." The other two boys looked at each other; Dart was excitable, but far from stupid. He must have seen something.

"Well, you were wrong! We were being listened to, there in the sitting room!"

Bowen started to rise from his wheel chair, then fell back as a wave of dizziness warned him that he could not stand unaided. Like the others, he knew that Dart was intelligent and his report called for a sudden change in plans if it were correct.

"How do you know? What did you see?"

"Well, ever since you mentioned spies I've been trying to figure out what ways we could be checked on in this house; it seemed to me that about the only way was to hide microphones of some sort. If anyone had done that, there would have to be wires going out; so I just looked for wires."

"And you found them?"

"One, yes."

"You're sure it wasn't the phone wire?" Dart gave his older brother a look of scorn.

"I'm sure, unless you've had a new drop run in while I was out—and fastened it to a matchbox-sized gadget stowed behind a picture in the sitting room."

"Which picture?"

"That two-foot-square thing of an Arizona sunset on the wall toward the kitchen."

"You're, crazy; even if the wire hadn't been put in till we went out this afternoon, I'd have seen it afterward while we were talking. I was facing that picture the whole time."

"Hadn't we better look, rather than argue?" asked Bowen. There was no answer to this, and the party headed for the sitting room, Dart leading the way and Peter bringing up the rear with the wheel chair.

"All right, bright boy. Why didn't you see it?" Dart was asking as Peter and Bowen arrived beneath the picture. Actually, there was every excuse for Bart's failure, for the tiny box which his brother had now pulled out into view had been completely concealed behind the heavy frame, and the wire leading from it was little thicker than a hair. It led up the wall, along one of the much heavier wires which supported the picture, along the molding next to the ceiling, until it reached a window opening onto the side drive of the Bowen house, and disappeared between the upper sash and the frame. It took several seconds for all the group to perceive this, since the wire was difficult to see even after its location was known.

After following it to the window with their eyes, Peter and Bart started for the door to find what it did outside, but Bowen stopped them.

"Wait a moment, boys. Dart, did you go out to see where it went?"

"Yes."

"What did you find?"

"It runs down to the ground right outside the window and ends in a box about three inches square and I don't know how thick, buried to its top in the flower bed and pretty well hidden by the plants."

"Do you know whether anyone was watching you while you examined it?"

"I didn't think to look. I didn't see anyone, either on the street or on the neighbors' grounds—or ours."

"Then it's possible, but not certain, that whoever installed this set doesn't know we've found it. I don't think it would be wise for anyone else to go to have a look, though."

"But why not, Uncle Jim?" asked Bart. "Won't they have already heard us talking in the last minute or so, and know what's happened?"

"I doubt it. Of course, it's possible that the box may be a radio, but I doubt that anyone would take such a chance; there's no such thing as a secret wave length, and they wouldn't have wanted to broadcast our talk to the whole world. I imagine that box is a tape or wire recorder; whoever is listening in on us will have to come back to pick it up, or at least its record. That gives us a chance to do a little thinking, since it won't be dark for a while yet and I shouldn't think they'd come by daylight. I could have the police waiting, I suppose."

"But wouldn't that mean that the tape would fall into their hands?" objected Dart.

"Probably; but why should that bother us? We haven't said anything that isn't going to be published soon anyway—in fact, it's probably on the air right now.

"Even the part about the chance of claiming a planet because you are first to land on it?" It was Peter's first remark for some time. Bowen was silent for several seconds.

"That's a point," he said at last. "Perhaps the civilian police would not be the best. The trouble is, I can't use military intelligence, since the project is not military."

Bart glanced at the other boys. They both knew what he was thinking; Dart grinned and gave him a "go-ahead" nod; Peter's expression did not change.

"Uncle Jim," Bart said carefully, "why wouldn't it be possible for us to ambush this character ourselves?"

The answer was prompt.

"Because it would be more risk than I can allow you to take if you aren't armed, and it would probably get you into trouble with the law if you were. I have every respect for your common sense, but very few people your age could resist the temptation to use violence in such a situation."

"We don't have weapons, and I don't see how we could arrest a spy anyway. What we could do is get a look at him—maybe a picture. I should think that might be a good deal of use." Even Peter nodded approval at this. Bowen was less easy to persuade.

"How do you get this picture without his knowing it? I don't want someone chasing you with a gun to get the film away from you, and I don't see how he can help seeing the flash as you take the picture."

Peter offered a solution to this.

"Have the flash set up as a booby trap, so that he'll spring it himself—or at least think he did. Then he may look for the camera, but he won't be chasing us."

"You mean you'll be inside, where it's safe? That seems sensible."

"What good will we be inside?" Bart cut in. "The idea is for us to see things. Besides, unless one of us is either holding the camera when the flash is set off, or else gets it and carries it away afterward, what's to keep the spy from finding it?" Bowen thought for some moments.

"I wish I could be out there to cover the business," he said at last, "but that will be a long time from now, if ever. Boys, I'm going to trust your judgement. I would like to be able to see this spy, but I would very much rather be able to keep the three of you around alive and healthy. I'm not going to make you promise anything, but I'm trusting you to look after yourselves first, and get pictures second. Make your plans carefully; you know the grounds here. I am going to have to sleep—if I can."

THE SPY

THE Bowen house had about half an acre of ground, mostly at the rear. It stood about thirty yards from a fairly well-traveled street. The entrance drive came straight in from a front corner of the lot—the left, looking from the house—and went back to a garage, with a turning loop branching off to the front door. The lot itself was surrounded by a five-foot brick wall on all sides except toward the street; there, the only privacy came from a thick boxwood hedge the same height as the wall. There was no gate; the drive came between the end of the hedge and the wall.

The sitting-room windows overlooked this drive, about halfway along that side of the house. Under them was a narrow flower bed. It was now March, and some of the early plants had grown tall enough to help conceal the recorder, which had been buried at this point. Across the drive was a row of tall bushes, forsythia and lilac for the most part. Some of the lilacs were old and stout enough to be called trees; the boys had sometimes climbed them when they were younger.

Behind the house was an open lawn with a row of fruit trees on three sides. Between these and the wall the bushes continued all around the lot.

The boys had known all this for years, of course, but for the first time they realized how easy it made things for anyone who wanted to approach the house unseen. The wall could be climbed at practically any point, under the cover of the lilacs; one whole side of the building was separated from the bushes only by the width of the drive, and the garage itself was almost concealed by them.

Half an hour's discussion resulted in no better plan than that the three should conceal themselves in the bushes along the drive: one opposite the front of the house, one at the middle, and one near the garage in back. There would be no chance to intercept the spy if he came, but it should be possible to see him as he crossed the drive. Both the Ranger boys had cameras, and these were to be carried by their owners. A flash unit was placed in the flower bed a few feet from the box itself, and arranged to be fired by strings leading to the hiding places of the photographers.

There had been no time for really ingenious booby-trapping, and in any case the boys did not want to be seen showing too much interest in the flower bed. Likely enough that they had betrayed themselves already.

Taking seemingly casual walks through the neighborhood, they had kept careful watch for anyone who appeared to be unduly interested in the Bowen property, but they had not seen any such person. As soon as it was reasonably dark, therefore, the boys slipped out through the kitchen door, crawled over to the garage, and worked their way down the line of bushes toward their stations. Peter was to be closest to the street; he had no camera, but stood the best chance of actually seeing the spy if he went that way, since there was a street light fairly close to the entrance of the drive.

Dart was to be in the middle, closest to the buried recorder, while Bart stayed near the garage. There was no way for them to communicate once they were posted; they would simply have to wait, as long as their patience permitted. None of them had thought to make any arrangements for reliefs; they had assumed without thinking that whoever was going to come would come fairly early. It occurred to each of the boys, as he settled down to his lonely watch and it was too late to do anything about it, that perhaps nothing would happen until two or three in the morning; even Dart admitted to himself that he might be a little slow with his camera by that time.

As it turned out, they needn't have worried about a long wait, though the person who came for the recorder almost fooled them in another way. They had supposed without thinking very carefully about the matter that he would come in at the side of the property on which the device was buried; actually, he must have climbed the wall at the back, and instead of coming down through the bushes where the boys were hidden, kept close to the opposite side of the lot until he was level with the back of the house. From this point he crawled with great care past the kitchen door to the corner nearest the garage; it was here that Bart first saw him.

There wasn't much to see—simply a dark patch, which at one moment was barely visible at the corner of the house, and by the next had worked its way between the building and the flower bed. Bart knew enough to look off to one side rather than directly at the thing, and was able to catch occasional glimpses as it moved slowly down toward Dart's station and the buried equipment. His hand tightened on the string with which he could fire the flashbulb, and he was already holding his camera, shutter open, so as to cover the moving figure; but he waited, hoping that there might be a chance to get a clear picture showing the spy's face.

Now the dark figure had reached the recorder. Any doubt about its mission had now vanished. Bart wondered whether Peter had seen it; he was reasonably sure that Dart had. It was motionless now—either digging up the whole machine, or replacing its tape or wire with a new one. Any moment now it should turn away, back the way it had come, and for at least a moment should have its face toward Bart's camera. The boy once more tightened his hold on the string, and leaned forward with his eyes boring into the near-darkness.

He never pulled his string, however. One instant he was staring tensely, ready to act; the next he had flung a forearm across aching eyes that saw nothing but a dancing mass of color. Dart had fired the flashbulb first.

A split second later several shouts echoed along the drive. Bart's was simply a wordless howl of mingled pain and annoyance; the spy uttered a very similar cry, but Dart had something to say.

"I've got him! Come and help, you fellows!"

"You young idiot!" howled his brother. "What do you think you're doing? Remember what Uncle Jim said? And how can I help you after you blind me?" In spite of this objection, he put down his camera and made his way toward the scene of activity.

Peter gave no answer in words; he simply came at top speed. By sheer luck, he had never seen the spy at all, and had not even been looking toward the house when Dart fired the flashbulb. Consequently he was not delayed by being blinded.

Dart continued to talk; apparently he was not completely occupied.

"I know we weren't supposed to get hurt," he said, "but this is just a kid; he couldn't hurt anyone." It was rather fortunate that Peter arrived just as this sentence was finished, for the spy promptly did his best to prove his captor wrong. A very hard fist caught Dart in the ribs—a few inches too high to wind him, but quite firmly enough to be felt. He tried to shift his grip to prevent another blow, and in the process the captive almost wriggled free. It was at this point that Peter caught the spy's free arm, arresting a swing which probably would have ended on one of Dart's eyes.

Even with both arms held, the small intruder did not seem inclined to give up the fight. He began making extremely painful use of his feet, and for several seconds the group looked rather like a troupe of dancers as Peter and Dart endeavored to keep their shins out of harm's way. Then Bart arrived, with his sight sufficiently restored to enable him to help, and the three of them finally managed to get all of their captive's limbs under control.

"I think he has eel blood in him," remarked Peter. "Who has the light? Let's see what we have here."

"Do that, by all means." Bowen's voice came from the window, which had just been opened. The boys had not realized that he could move the wheel chair himself. "We'll let your captive explain what he's up to, and then I think a little more explaining is due from other people."

Dart was glad that the darkness hid his worried expression. He also hoped Mrs. Lynn had not heard the disturbance; she had not been told about the evening's program, and had firm ideas about sleeping requirements of teen-agers.

"Well, Uncle Jim, I know you said we weren't to take any chances; but when I saw how little he was, I decided there wasn't any danger—"

"Bright, aren't you?" Dart's remark brought both words and action from the captive. "I may be smaller than you are, but I'll take you on any time, at anything you want, just as long as you'll keep your big bodyguards off." One of his feet jerked free from Bart's grip and was planted firmly in his younger brother's stomach, and Dart was silent for some moments. The aim had been better this time. Then a flashlight held by Bowen illuminated the whole group, and the Rangers and Peter looked with interest at their captive. It was just as well that they did; it was their only chance for some time.

He was small enough to explain why Dart had called him a "kid"—several inches shorter than Dart himself; he could not have weighed much over a hundred pounds. His reddish hair was cut very short, and formed a brush over a face which looked at the moment as though its owner carried a permanent chip on his shoulder. It was hard to judge his age, but Bowen, making allowance for the poor light, decided that it was less than Dart's, and wondered how such a youngster had become involved in this sort of undertaking—and why anyone would use such an agent. From a look at that stubborn face, it seemed that it was going to be hard to find out, but there was no harm trying.

"Young fellow," he said, as severely as he could, "I suppose you see that you've managed to get into a good deal of trouble."

"I'm not worried," was the answer.

"I'm not to blame for your lack of common sense. The fact is that you're trespassing, and there's not a policeman in Maryland who wouldn't cheerfully arrest you on a charge of larceny—"

"What's that?"

"Stealing, in plain English."

"What have I stolen?" The young face wore an impudent expression. "I haven't taken a thing of yours."

"No? Boys, did he get the tape from that recorder?"

"I think so," said Bart and Dart simultaneously. "Just a minute and we'll see." Dart started to go through the captive's pockets, but stopped at his next words.

"What if I did?" asked the redhead. "It isn't yours, so how could I be stealing it from you?"

"It's on our property. Whose is it if it isn't ours? What would you tell a policeman?"

"It's—you're pretty smart, aren't you?" The youngster saw the trap in time, thereby earning the startled respect of Dart and Bart, who had not. Bowen showed no sign of annoyance, but continued his questioning through the window.

"What's your name?"

"Wouldn't you like to know?" That answer told Bowen more about the youngster's background than the redhead ever guessed, but the man did not betray the fact. "Was it you who placed the microphone inside this house? That would certainly constitute an illegal act, wouldn't it? Breaking into someone's kitchen, even if you only left things instead of stealing them, is quite—"

"It wasn't—" the captive interrupted, but did not finish his sentence. His lips pressed firmly together in an obvious determination to say no more.

"So you don't always catch the traps in time, my young friend? 'It wasn't the kitchen,' you were going to say? Quite right, but how did you know?" There was a moment of silence.

"There's a blower in the wall at the back; the kitchen must be there."

"Very good; but if you knew that already, what bothered you a moment ago? And did you see that blower when you came tonight? Pretty dark for it to show up, isn't it?" He paused, and continued more gently, "I think you can see we have a case. We'll talk this over inside, where everyone will be more comfortable, and perhaps you can convince us that there's no real need to turn you over to the police. However, you must realize that we have pictures of you— I take it, boys, that you did get pictures?"

"I guess so," replied Bart. "My camera was open and pointed in the right direction when the flash went off. We won't really know until they're developed."

"All right, take a couple of more shots while you have the chance. Then our young friend will know that we can always have him picked up if it becomes necessary."

"We don't have any more flashbulbs out here, Uncle Jim. We'll bring him inside, and take them there while you talk to him."

"All right."

But it wasn't all right. The spy had ideas of his own on the subject of pictures; for one thing, he knew perfectly well that he had not been facing the bushes when the flash was touched off—if he had been, he would not have been blinded by it and these clumsy fellows would never have caught him. However, if they were to try again, he could hardly count on their not getting good pictures, and if they did, his usefulness would be over.

As a result of this conclusion, a rather interesting thing happened. As the boys turned toward the front door, with Dart and Bart each holding an arm of the young spy and Peter walking just ahead, the redhead vanished—at least, that was how the brothers described it later. For a split second no one realized just how it had been done; then they saw that he had somehow twisted his arms simultaneously away from the hands holding them and ducked away from Peter.

For a moment it looked as though the attempt had been wasted, for the small fugitive's move had brought him almost against the side of the house with all three of the boys blocking his way to freedom; but as they closed in in a concerted rush, the spy went up. One hand on the window ledge and one on a shutter, he leaped; as Dart and Bart collided below him, he braced a foot against the ledge and dived over them with seeming recklessness. Peter, slower than the others, had not become involved in their tangle, but he had no chance against the nimble little figure. He landed almost within arm's length of Peter, but had somersaulted in the air so that he came down ready to run—in fact, already running.

By the time the others had picked themselves up and started in pursuit, the spy was halfway down the drive; as the pursuers' footsteps warned him that he might be caught in a straight race, he swerved toward the wall, reached it at a gap in the bushes, and went over it in a way that brought a whistle of admiration from all three boys. When they got their heads over the wall, there was no sign of the redhead; he was undoubtedly hiding in the neighborhood, but searching for him in the dark was obviously a waste of time. The crestfallen boys went back to the house, one of them, at least, making plans to take up a new sport after the spring vacation.

PETER TALKS FAST

UNCLE JIM showed a mixture of annoyance and sympathy the next morning. He had slept better than usual, which gave some hope that he might eventually recover from his "long fall," and this was probably the source of most of the sympathy. He expressed most of his annoyance, not at the spy's escape, but at what he called the complete lack of horse sense shown in the original attempt to capture him. He did admit that Dart's recognition of the spy as a young boy was some excuse.

"But there are kids that age who have been arrested for carrying knives," he added, "and you were still taking a chance. I'm forgiving you this time, but don't get the idea that I'm pleased."

"If we'd kept him you wouldn't be so bothered."

"It's because you lost him that I'm forgiving you. You knew perfectly well that I didn't want to turn him over to the police, and that there was no other legal way of keeping him. What would we have done with him? That was another reason why I didn't want you to do any more than get pictures, and I'm just as glad he got away. How did the pictures come out, by the way?"

The boys had wanted to examine the pictures the night before, but Uncle Jim had ordered them to bed—Peter had, of course, telephoned his home long before to warn his guardians that he would be spending the night at the Rangers'. Dart's objection that it would take only a few seconds for the films to develop had not been allowed. Now, at Bowen's question, the brothers got their cameras, pressed the "develop" buttons, and a moment later the group was examining the prints.

Both showed the spy, but neither showed his face at all clearly—Bart's, of course, did not show it at all; the small intruder had been facing away from him when the flashbulb was fired. The other picture was in profile, but was not as clear as it might have been, and the boys at least had one defense for their action. If it had not been for the attempted capture, no one would have been in a position to recognize the spy, should they ever meet him again.

"I don't suppose we will, though," said Peter. "With all the stuff in this morning's paper about the satellite station, it would hardly do much good to spy on us—or on anyone connected with the business."

"You may be right in a way; but that was also true to some extent before. It was widely known for more than a week that there would be a news release last night. Someone must feel that we're keeping something concealed; and if they believe that, they'll go right on spying. I suppose in a way that might be good; we released the facts to get ideas from the public, and if these folks listen to us they may actually learn less than they would in other ways. I've been in the business from the beginning, and admit I'm out of ideas."

Peter started to say something, but stopped before the words had formed. Bowen was about to go on with his remarks when the expression on the boy's face caught his attention. He looked at him narrowly for a moment.

"Pete! Do you mean you do have an idea about this matter?" The others looked at the "bookworm" expectantly, but Peter did not answer directly. He asked a question of his own instead.

"Did anyone check to see whether our little friend had put a new tape in that recorder? We know he got away with the old one."

They had decided the previous evening not to try to remove the listening device without further thought, and no one had looked to see whether it was still in working condition. Bart hastily went out to determine this point, and returned in two or three minutes with the news that the reel magazine was empty. Evidently the redhead had not had time to replace the one he had taken. This appeared to relieve Peter.

"All right," he said, "I do have an idea. I can't tell how good it is, but I don't think anyone else can either without trying it. Tell me, Uncle Jim, did anything ever happen to those monkeys they sent out on that two-week orbital test several years ago—the one where they used old-style rockets, and were trying to find out what weightlessness would do? I read about the test, but nothing much was ever said about what happened to the test animals—most of the reports just bragged about all the automatic controls they tested at the same time."

"They suffered no apparent ill effects," replied Bowen. "They were all alive when the pay-chamber of the test rocket was parachuted back to the surface, and I believe one of them is still alive. That's why this business took us by surprise; we assumed that if a monkey, who certainly couldn't understand what it was all about, could nevertheless stand the sensations, then a man should have little trouble."

"That's what I thought. That, and something you said last night, started me thinking."

"Duck, everybody!" remarked Dart. "It's one of Pete's ideas!"

"Of course, people who are afraid of ideas can stay on the ground," Peter replied pointedly. "But my point was simply this: doesn't it seem likely that the trouble is caused by learning? That a grown man, who has spent years getting himself used to situations which always include weight, simply can't unlearn all that when the weight disappears?"

"That's about what I said last night," remarked Bowen.

"I know. However, short-lived animals like monkeys, which aren't too well equipped for learning anyway, had no trouble. Wouldn't it seem likely, then, that the younger a person was, the better his chances of getting used to space?"

This question was received in silence, while Bowen and his nephews digested its implications—and Dart came as close as he ever had to apologizing to Peter. Even he could see where this line of thought was likely to lead. He said nothing, however, for he could see the sort of objections likely to be raised, and felt that the originator of the idea was best qualified to fight for it.

Bowen could see what Peter had in mind, of course, but chose not to admit it at first.

"You mean, I take it, that newborn children could get away with lack of weight? I see two objections. One is that they couldn't operate controls anyway, and the other is that you're wrong—the sensation of weightlessness is one of endless falling, and that's one of the few things that does bother a newborn child."

"But it doesn't bother a six-year-old nearly so much. That helps my point. As a person grows older and his brain improves, he learns that falls of a certain distance are not dangerous—we've all seen kids jumping out of trees. Then later he gets the idea more and more firmly fixed that above a certain height it is dangerous to fall, and winds up in the situation you're in. It seems to me that there should be a happy medium somewhere, where a person is grown-up enough to learn to handle machinery, but not so set in his thinking that he can't get used to new conditions. I don't know that that's the case, and I certainly don't know that Bart and Dart and I are at the right age even if the idea is sound; but it seems to me that it's something worth testing."

Bowen thought for some time before he answered.

"You certainly have some sort of idea there," he admitted at last, "but there are more difficulties than you seem to have considered. The most obvious one is the matter of having fifteen- and sixteen-year-old boys gadding around through the solar system with no supervision. I'm not saying that I don't trust you myself, but you can see how a lot of people would react."

"Isn't that a problem which won't really come until after the idea proves possible?" asked Peter. "If it turns out that we can stand constant fall, then we can tackle the problem of making it legal." Bowen noted with amusement the smooth way in which Peter had gone from mentioning young people in general to "we."

"Even the first trial would be a problem that way, though. What parent is going to let his teen-ager fly a rocket—particularly when it won't be possible for any adult to teach him how, at least not in the way flying is usually taught?"

"You'll just have to use boys without parents, I guess."

"Nice try, Pete. Unfortunately, a legal guardian is in an even worse position than a parent, as regards what he can allow his ward to do. I suppose I might possibly arrange it for Dart and Bart here, thought it wouldn't be easy—I'm a blood relative of theirs, and their 'natural' as well as legal guardian. In your case—well, I don't know what we could do. I assume, of course, that you're casting yourself as well as my nephews in the role of test pilots."

"That was the idea," admitted Peter.

Bowen nodded, and the brothers perceived with delight that he wore an expression suggesting that he was willing to be convinced.

"Hmph. What do the school authorities say when I cart you off with the story that I need you for guinea pigs?"

"You took Bart and Dart to Africa four years ago."

"That was supposed to be educational. I had to agree to spend a certain number of hours a week teaching them, or seeing that they were taught, material which the school board had selected."

"Well, can't you do that here? Or would you even need to? This sort of thing would be about as educational as anything we could possibly be doing."

"There's something in that, I suppose. Certainly a young man majoring in physics would profit by it. I'm not so sure about a couple of track stars, of course; it's hard to see where running or jumping could help or be helped by space travel."

The brothers stiffened at this remark. It seemed probable that their uncle was joking, but there was enough doubt about it so that they both felt the need to say something. They looked at each other in some consternation.

"Wait a minute!" exclaimed Dart. "It seems to me that running and jumping will be a darned sight more useful in a place where you have to use your muscles than sitting in a chair reading a book—or swimming!" Peter had his answer ready.

"I don't know about the swimming end, though it seems to me that moving around without weight will be a lot closer to that than to running, but how about diving? How's a fellow who still depends on luck for what happens between the end of the diving board and the water going to know which way is up out in space?"

"There isn't any up, so what does it matter?" retorted Dart.

"Well, it will be nice to find out which is the best preparation," Bart cut in. "After all, it would be foolish to use only one guinea pig in any experiment." Dart grinned at this, and the argument ended; the brothers had made the point they wanted. Bowen took up the discussion once more.

"There is still the matter," he said, "law or no law, school or no school, of putting you fellows into any position of risk. I know that you don't object, but whatever sort of brains you may have, you still don't have adult judgement; if anything did happen to you it would be my fault. I know Pete's folks will feel the same."

"We wouldn't blame you."

"That's not the point; I'd blame myself. So would Peter's guardians, and so would the law. You know it perfectly well. With no reflection on your abilities, I'd feel about the way you would if you told a three-year-old that it was all right to cross the street, and then saw him hit by a car."

There seemed at first no answer to this. While each of the boys felt that he would certainly be able to take care of himself in any situation which was likely to arise, they also knew in their hearts that Bowen's feeling was perfectly justified. Bart even wondered whether it was fair to try to persuade his uncle, considering his present condition. After all, had James Bowen been in his normal state of health, none of this discussion would have occurred; he would have heard Peter's idea, thought it over for about thirty seconds, come out with a definite "yes" or "no," and that would have closed the matter.

If Peter felt the way Bart did, however, he managed to keep his attitude under control. He wanted to get into space and see for himself the worlds that he had read about; he wanted it as he had never wanted anything in his life, and he was prepared to ignore the finer points of fair play to get there. Therefore, during the brief silence which followed Bowen's remark, he mustered his thoughts for another attack.

"Uncle Jim," he finally asked, "just how important do you think it is that we do get out into space? What good will it do the country or the world?" Bowen leaned forward and began answering, earnestly and without hesitation.

"I think it's one of the most important things that can possibly happen right now. In the last three or four centuries the sciences which have been keeping mankind alive have been suffering more and more from the fact that all their observations were from the viewpoint of one world. That viewpoint kept Tycho Brahe from realizing the true nature of the solar system, which didn't hamper the rest of science much at the time; but it was more serious when Lowell drew canals on his maps of Mars and Ganymede and when Michelson and Morley tried to find the actual speed of the earth. It's become worse since; researchers in physics, chemistry, nucleonics, meteorology, and literally dozens of other really important fields—important in that we need them to keep the population of the earth alive—are being hampered because they can't observe the earth from outside or because they can't get weight-free conditions or cold enough conditions or oxygen-free conditions in a large enough space— I could go on half the day, but you see what I mean.

"Then, if getting into space is so important for mankind, have we any right not to try any plan which has a chance of working, regardless of how much worry it may cause or how much danger may be involved?" Peter stared straight into Bowen's eyes as he asked this. Now he was serious; it was not just a matter of finding an argument which would let him personally reach the moon, but a feeling of urgency which matched Bowen's own. Bowen himself realized this, and very slowly nodded.

"You're right; I haven't," he admitted. "I'll do what I can to try out what you have in mind, and to persuade your folks to let you in on it too. Thanks, Pete; that was a very, very good point."

NIAGARA

FORTUNATELY, Peter's guardians knew, respected, and trusted James Bowen. They also felt about Peter as though he had been their own son, however, and they were naturally dubious about the proposal. Bowen's own condition was not very encouraging; the agreement finally reached was that if Bowen himself showed reasonable improvement within the next few weeks, and if nothing serious happened to any of the crew of the satellite station now in space during the same period, then Peter would be free to do as he pleased in the matter.

This waiting period solved another problem; it removed the need for, getting the boys out of school before the normal summer vacation. That took care of Peter permanently in that respect, since he was graduating, and the Ranger boys would not have to worry about the matter until September. If they were at all disappointed at not getting out of the spring term at school, they had the sense not to say so.

The principal anxiety for all of them, naturally, was James Bowen's health. This was not entirely a selfish feeling; as Bart remarked to the others one day, it gave him a queer feeling in the stomach to see the man they had always regarded as one of the strongest and bravest in the world unable to stand on his own feet.

However, as the weeks passed, he did gradually improve. He slept better and better; the nightmares in which he would wake up grasping at anything solid in reach to stop the endless falling sensation gradually became fewer. He learned to stand again, at first for just a few seconds by dint of using his eyes and ignoring his undependable sense of balance; bit by bit, as his nervous system began to trust his semicircular canals once more, the balance itself improved. By the middle of May he could keep on his feet with his eyes shut.

Then it was simply a matter of getting his strength back, since two months in a wheel chair had not given him much exercise. By the time the schools closed he was perfectly able to get around by himself and do a certain amount of work, though he was not yet the man he had been. Peter's guardians were satisfied, to that young man's frank relief, and the day after school closed the four of them boarded a plane for Niagara. Three of them were looking forward eagerly to the prospect of the "long fall," while the fourth very definitely was not. He felt strongly that enough was enough.

There had been no further detected attempt at spying on the Bowen home. They could not decide whether the discovery of the first try had discouraged the unknown people responsible, that they had found out all they wanted to know—or that they had taken up some more efficient method, and simply not been caught at it. Bowen and Peter had thought of that last possibility, though it had not bothered the Rangers. None of them had caught another glimpse of the redheaded athlete who had escaped them the first night, though all three of the boys had kept their eyes open for him.

The satellite station had not been out of the news since the first-announcement, and the classmates of the boys had been bombarding them with questions of all sorts regarding the project, since it was generally known that Bowen was connected with it. It is hard to guess what might have happened had their friends learned that Bart, Dart, and Peter were to attempt to fly rockets and actually visit the station, but Bowen had requested that they keep the matter secret. He had no desire to receive several bushels of letters from horrified parents, and still less to have someone bring legal pressure to stop the matter. He was convinced that he was doing right, but realized that many others did not share his feelings about the importance of space flight. Several times one or another of the boys almost let the matter out, since it was hard not to brag; but as far as they could tell, no one had suspected the truth up to the time they left.

The flight was uneventful. Forty minutes after the doors of the plane closed at Washington the group was walking down the exit ramp at the Niagara field, and a few minutes later they had been driven to the outskirts of the city and the great building of the aluminum plant where the parts for the satellite vehicle had been made. This was a scene of considerable activity, for although many people now felt that there was no future in space flight, a great deal of equipment for that purpose was still being made. Most of the plant was open, but a number of sheds were closed and guarded; and it was into one of these that Bowen took the boys. The guard recognized Bowen and let the whole group in without comment.

The boys had hoped to be introduced at once to the rockets they were to try to fly, but a good deal had to be done first. Their initial experience on entering the building was with a complete medical laboratory, and they spent the rest of the day being examined with a thoroughness they had never before seen. Peter was moved to comment toward the end of the procedure.

"I think there's a blood corpuscle in my left little toe that you missed," he remarked.

The doctor working on him at the moment was able to hold his own in that sort of talk.

"There are two more near your right elbow. We don't care about those; they'll be gone by the time you take off anyway. Tell me, when did you have that skull fracture?" Peter gasped, while visions of being grounded for medical reasons danced through his head.

"It's never been fractured! I never was even knocked out!"

"Really? You mean wisecracks like that came in through the regular channels? I find it hard to believe." Peter realized he had met his match, and made no more remarks.

The examinations included a set of measurements of a very complete nature. Dart, undeterred by what had happened to Peter, asked whether the rockets were going to be tailored to fit them. His Uncle Jim answered this question.

"No, although the one-man rockets are pretty cramped gadgets. What really has to fit, though, is your vacuum suit. You'd feel a trifle silly if you put the thing on and then couldn't move because the knees were half an inch too far down the legs."

They thought the examination was over at the end of the first day, but on the second, they were introduced to the Barany chair, a device which had been used for many years in checking airplane pilots. It was a chair of the revolving type—not revolving when the person sitting in it wished, like an office chair, but spinning under the influence of an electric motor in its base. The control of the motor was not in the chair but on a panel well out of reach, and this feature, together with a set of safety belts attached to the chair itself, caused the boys to eye it somewhat uneasily. Bowen seemed amused about something.

"Well, Pete," he said, "this will give some sort of test for your idea. This thing used to serve to show whether or not a pilot's sense of balance was normal. They spun him for a while and then turned him loose to walk a straight line—if he could."

"And he was supposed to be able to?"

"No. He was expected to be dizzy. If he wasn't, something was wrong with his semicircular canals. I expect you fellows will be dizzy at first, too. However, if there is anything to your idea, Pete, it may be possible for you to learn to overcome—no, that's not a good word—to allow for dizziness. I don't see why my advice should be much good, but it would seem that the thing you'd have to do would be learn to ignore your feelings and trust your eyes alone. I don't know whether it's possible, and even if it isn't you might still be able to get used to weightlessness; but we're going to try this anyway. Who's first?"

This question started a brief argument, the brothers claiming that since the basic idea was Peter's, he had the right to go first, whereas Peter insisted that Dart, as the youngest, was the logical candidate. They finally settled it by matching coins, and Dart turned out odd man. He seated himself with rather mixed feelings, while the others watched closely. The medical technician at the switches called out, "All aboard!" when the safety belts were fastened and checked, and the chair and its occupant began to turn—not too rapidly the first time, and for less than a minute. Then it was stopped, the straps were released, and the straight line painted on the floor was pointed out to the staggering Dart.

He did fairly well, all things considered, but was in no position to deny that he had been dizzy.

"I think your idea is right, though, Uncle Jim," he said when the trial was over. "If I can learn to believe just my eyes, I think I can do it."

The others followed in their turns, doing about as well as Dart; all insisted that they would be able to control themselves with a little more practice. Bowen was not sure whether they were right, or simply felt that failure here would cancel the whole plan.

"We're not going to give you much practice," he said. "After all, although this does throw your sense of balance out, it doesn't do it in the same way that space travel will. This was just an experiment; you'll do it a few more times, at different speeds and for different lengths of time, also for experiment. This can hurt you, after all, and I'd rather you took your damage in some more useful way."

"What else is there to do, then?" asked Peter.

"Actually, it's hard to say; no one has ever been prepared for space except the crew who went up with the station on the first trip, and we can't say that they were very well briefed. We have to wait for a few days, since your suits won't be ready until then; in the meantime, we were planning to check your acceleration tolerance and then get you. familiar with the ships you'll fly if the whole plan works."

The check Bowen had mentioned involved another chair, but this one was set at the end of a long, pivoted, counterbalanced arm. The boys had seen pictures of such devices, and knew that the chair was swung so that centrifugal force tended to throw its occupant outward; and it could reach a speed sufficient to make that force several times that of gravity. Dart, for example, could in effect have his weight raised from its normal one hundred and thirty-five pounds to twice, or three times, or even six times that value—that is, he could be put under two, three, or six "G's" if he could stand it.

As before, this was more of an experiment than a practice session, and a few modifications had been made so that they might learn from it. An imitation instrument board had been placed at the pivot so that it would face the spinning chair constantly and could be read from it—if the occupant were in any condition to read. Bowen wanted the boys to realize that acceleration could interfere with their normal abilities before they became aware that anything was wrong.

Peter was first, this time. At two G's he was somewhat uncomfortable; at two and a half, his eyesight began to suffer—he was reading very peculiar things on the instrument panel. At four, his eyesight failed altogether as the blood was forced away from his eyes by its own extra weight. The Ranger brothers laughed at his attempts to fight off the effects, but they both stopped laughing when- their own turns came. Bart stood just about as much as Peter; Dart, shorter and solider than the others, took about half a G more before his eyes became untrustworthy.

"It's nothing to brag about," cautioned Bowen. "I just want you to see that you'll have to be cautious about using power in the rockets. You can get in serious trouble if your brain starts losing blood where no one can even warn you, much less give you any help. Be careful!"

The boys would have paid more attention to this warning had they not been looking forward to training in their rockets, which Bowen had said would come next. They were a trifle disappointed to find that the training would be synthetic, in imitation control cabins similar to the old Link trainer. It was better than being spun dizzy, however, and they kept telling themselves that the actual take-off could not be delayed much longer.

The centrifuge test had used up most of a morning; Bowen, who had other work to do, suggested that they eat lunch and meet him at the building where the trainers were located. They had long since been given the run of the plant—even guards who did not know them personally knew about them, and the boys had no difficulty entering or leaving the buildings. They ate rather quickly, since they wanted to see the controls they would have to learn, and hastened to the building where Bowen had told them he would meet them. For the first time, a guard stopped them.

"Wait a minute, fellows; no visitors." He was not a man any of them had seen before, so Bart began to explain their position at the plant.

"I know about that," the guard interrupted, "but even your job doesn't mean you can bring visitors. I was told there are only three of you. I don't know which of you is which, but the extra one can't come in."

"What do you mean?" Bart honestly wondered for a moment whether the man were sober. "There are only three of us here."

"So I see. Three and one make four. What about the one already inside?"

"What? Already—"

"Yes. Already. Did one of you get his wires crossed? The little fellow with the red hair went in half an hour ago."

TUMBLE

BART instantly realized what had happened. "Are there any other ways out of this building?" he asked.

"No doors. The windows are too high to be reached from inside without—"

"Don't kid yourself. That fellow could probably go straight up a plaster wall." The acrobatic ability of the redhead was the thing which had remained most firmly in the memories of the boys. "Please telephone for enough extra guards to cover the windows. We'll stay with you, so you won't have to worry about whether we're trying to pull something on you. Warn the guards that the person who spied on the Bowen house in Washington is inside the plant—I think Uncle Jim must have told about that to the officials here. If he hasn't, though, tell them that they're facing the best broken-field runner they ever saw—I'd bet this kid could get a football all the way down a field with both teams trying to stop him."

The guard did not argue; he could see what must have happened. It was not an error which would have been made in a war-conscious country where everyone was security-minded, but it had been long enough since the last serious disagreement between nations so that the guarding of scientific secrets was not being taken too seriously. In spite of that, the guard realized perfectly well that if the spy he had let into the building got away again, he himself would probably be looking for a new job.

He picked up his phone and relayed the information that Bart had supplied. During the minutes that it took the help to arrive, the boys were scarcely able to remain still; all of them were picturing the redhead's making his way out one of the windows and vanishing as he had before. It was broad daylight this time, it was true, but they felt that the little fellow would never have come if he hadn't felt just as well able to take care of himself by day as by night. Once Dart went to the corner of the building to see whether their quarry was getting out on that side, but his brother called him back.

"Hold it. The guard here has no way of knowing that we're not doing something funny, too. We stay here until Uncle Jim or someone else in authority comes and identifies us." Peter nodded approval of this, and Dart came back.

After what seemed an incredibly long time to the boys, a group of a dozen guards appeared, and to their joy Uncle Jim was with it. In a few words they confirmed to him what he had already heard indirectly. Immediately he told all the guards but two to spread out around the building.

"The boys, you two, and I will go inside," he concluded. "If this fellow is still there, we'll try to get him. Close and lock the doors after us. You on the outside, stand away from the building; if he goes out a window and you're under it, he'll go right over your heads. I have the outer fence patrolled, too, but I'd rather he didn't get that far. Does everyone understand his job?"

The guards claimed that they did. It was evident that some of them felt Bowen was exaggerating the spy's abilities, but they surrounded the building as he had ordered. Then the boys, Bowen, and the two guards he had designated went inside and the door was closed after them. Bowen stayed by it until he heard the lock click.

"All right," he said, "now we have the job of finding out whether he's still here—and catching him if he is. This building is mostly one big room, but there are some smaller offices at the far end where he could hide, and of course the machinery on the floor here is big enough to hide a couple of football teams. Our first job will be to go around the walls and check on every window. They are supposed to be latched from the inside, though there are no real locks on them. If the latches are all closed, we can assume he's inside and go on from there.

"We'll split in two parties. Dart, one of the guards, and I will go to the left; Bart, Pete, and the other guard to the right. Call out if you find any window unlatched or open."

It was not possible to see all the windows from the door, since many of the machines on the floor were a good deal taller than a man, and cut off the view. The party spread out as Bowen had instructed, Peter and his group turning right and proceeding along that wall. They went rapidly at first, since all the windows in this wall were visible, but they had to slow down after they reached the corner and made their first left turn. At this point, naturally, they lost sight of the other party. The windows were well above eye level, and it was not easy for the guard to see how anyone—least of all a boy not much over five feet tall—could get to them, but Bart and Peter knew better. They checked each one carefully, particularly those within six feet of any of the taller machines. They had had one experience with the redhead's jumping ability.

Even with this care, they must have gone faster than the other group, for they reached the corner at the end farthest from the door earlier. It was Bart who first came around the last machine, and who saw the spy at virtually the same instant. The small fellow had apparently intended to enter one of the offices whose doors opened in this wall, but Bart's yell told him that he had been seen, and he evidently realized that he could be easily cornered in such a room. He reversed his direction instantly and disappeared between two bulky pieces of equipment. Bart leaped after him, but in the second or two it took to reach the point where the other had disappeared there had been time to dodge behind any of a dozen machines.

"Uncle Jim! He's still inside—somewhere in the middle of the room! Are all your windows fastened?"

"Yes!" came the instant answer, as Bowen's group appeared at the far corner. "Where did he go?"

"There." Bart pointed. "He could have dodged a dozen times and be anywhere in the room by now, though."

"All right. You and I," Bowen spoke to the older of the guards, "are probably slowest. You stay at this corner and watch the two walls you can see; I'll get to the opposite one and cover the other two. If you see him try for a window, call 'north' or 'east' according to the wall he's at. The rest will scatter through the room, looking at, under, over, around, or inside everything as you go. Anyone who sees him, give your location briefly and loudly—`a little northeast of the center' or something like that will be enough—and tell in which direction he's going if he's not cornered inside something. The others will try to intercept him. I'm betting he won't corner himself; it will be work for us."

"Wouldn't it be better to organize in a line, and sweep across the room slowly, covering everything as we go?" asked Peter.

"No, for two reasons. One is that we haven't enough people to make a solid line; second, anything that regular can be worked out by the opposition, and he can then make definite plans to get around you. If we're searching at random, he'll never know when one of us will stumble across him, or vice versa. All right, let's go." He headed for the corner he had assigned himself. The others scattered, except the guard who was to remain in position.

The first call came even before Bowen had reached his corner. It was from Bart, as he caught a glimpse of a form too small to be his brother vanishing behind a dummy control cabin.

"Near the northwest corner!" he called as loudly as he could. At the same instant he leaped toward the point where the fugitive had disappeared; then he checked himself as a thought struck him. Where he was standing, he could see between the machines all the way to both the north and west walls; if he stayed where he was, the spy could not cross his line of sight in either direction without being spotted. If Bart attempted to follow there would be no telling where the little fellow might go. He controlled himself, therefore, held his position until the others arrived, and explained the situation to them. They immediately moved into the much smaller area where the spy must be and resumed the search, while Bart remained where he was to call a warning if the fugitive crossed his line of sight.

This did not happen, and it seemed likely that the quarry would be sighted again very quickly, but minutes passed without a call horn anyone, and Bart began to grow uneasy. Had he failed to watch closely enough? He could hardly believe this, but he grew more and more worried as the minutes passed.

Peter, prowling among the machines, was also bothered. The area in which the redhead had to be was small—about twenty yards one way and not more than a dozen the other, perhaps a tenth of the whole floor space in the great shed. It was occupied by four of the big, cylindrical affairs which he understood were imitations of the control cabins of the rockets, and about twenty smaller assemblies, such as motors. Any of these would be big enough to hide behind, but it seemed strange that with several searchers the fugitive could be "behind" something all the time. The most obvious way around that argument was that he was not in the area, but there had been no alarm from Bart.

A person could, of course, get inside any of the four training dummies, but Peter felt the way Bowen had about that possibility; the spy would hardly corner himself in a place like that. Nevertheless, after some minutes of fruitless search, he decided to inspect the interiors of the devices.

They were about twelve feet high and eight in diameter, made in imitation of the nose section of the one-man rocket which had been designed at the Niagara plant and, so far, had never been used. A rectangular door seven feet long and three wide opened at one side, its bottom about four feet from the floor of the shed. All these doors were closed, but none was locked, though they had the regular sealing machinery which the real rockets were to use. Peter, after a moment's thought, examined one of them carefully and found that it could be dogged shut from outside; so before looking in any of the devices, he quietly went around to all four of them and sealed their doors. That would keep the fugitive inside if he were already there, and delay any attempt to dodge into one if the pursuit grew too hot for comfort. During this operation Peter met Dart, who had also had no luck, and explained what he was doing.

"I get it," the younger boy said. "Have you got them all locked?"

"All but this one," replied Peter. "Why don't you stand by while I look inside it? You run faster than I do, and might have a chance if he comes out over my head."

"All right." Dart stood back a little way, and Peter opened the door.

It opened outward, like those on the real rockets. Inside it, scarcely a yard away, was another; the space between served as an air lock if it should be necessary to leave the ship while outside a breathable atmosphere. Peter opened the second door and stepped through.

Directly in front of him on the far wall, four or five feet away, was an instrument panel which for a moment almost made him_ forget his reason for being there. It was not as complicated as he had expected, but there were a number of dials which were not labeled and whose purpose he could not quite understand. For several seconds he examined these before remembering with a start that he was not there for training at the moment. Then he looked around the little room.

It was a cylinder, seven feet in diameter and six in height, with the side opposite the instrument panel cut into by the air lock. Above, in the real rocket, would be the nose of the ship with ports through which it would be possible to see out; in this mock-up, there was a flat ceiling which Peter suspected could be used as a movie screen for training purposes. He could imagine a picture of the moon being thrown on it, expanding as though the rocket were falling onto its rough surface while the student inside operated the controls in an effort to avoid the simulated crash.

Below was a circular hatchway leading to a tiny food storeroom and then to the longer rooms containing the necessary machinery for keeping the air breathable and for condensing water; below—or behind—that would be the engine room. In this model, the hatch led only to a small space under the floor, scarcely two feet deep; and Peter lay down and put his head through the trap to make sure it was empty. Then he went out through the air lock to the waiting Dart.

"What took you so long?" Ranger complained as Peter stepped down the two-foot drop to the outer floor.

"I had to make sure," was all Peter said. "Let's dog this one shut so he doesn't sneak into it behind our backs." He suited action to this remark, and the two went on to the next mock-up.

One by one the four were examined, found empty, and locked. Still no cry had come, either from Bart or the guard who was searching with them.

They took the time to check with Bart to make sure that the spy had not managed to sneak out of the area, and found him worried about just that possibility. The guard joined them, equally mystified; while they were wondering what could have happened and what they should do next, a faint sound reached their ears. It was a barely audible scraping, but they turned toward it instantly. Nothing was visible, but after a moment Peter gave an exclamation that was mostly disgust at his own stupidity, and leaped for the nearest of the mock-ups.

While the others watched in bewilderment, he opened its door, which he and Dart had dogged shut again after the inside search; then, instead of going into the machine, he leaped up to the sill, jumped again and gripped the top of the door, and by bracing himself between it and the frame managed to get up to its top. This brought his eyes well above the level of the top of the machine; and as he reached this point he called out.

"This one! He's jumping off the other side!" The three watchers instantly started around the mock-up.

The spy had not attempted to jump all the way to the floor. As Bart came around the big cylinder, he was just recovering from a landing on an engine block standing near the mock-up. He saw pursuit coming, and made another leap before he had fully regained his balance.

That was his mistake. Agile as he was, he left the block a trifle sideways, and landed on the far side too greatly off balance to keep on his feet. Everyone in the room heard the crash as he struck the floor, for a loading dolly was standing at the spot where he touched. It was mounted on casters, and its brakes were off. It rolled as he touched it, depriving him of any small chance he might have had of recovering his balance; his feet went with it, and he landed on the flat of his back. Before he could recover, Bart was on him from one direction and Dart from the other. He wrenched once in an attempt to get out from under them, but stopped with a grunt of pain; one of his ankles had been hurt in the fall. The boys had their spy.

UNCLE JIM

TALKS STRAIGHT

THEY didn't really believe it. They expected that he would vanish from between them as he had before, but after the first attempt that had betrayed the twisted ankle, he made no effort to get away. Three minutes after his fall, he was seated in a chair in one of the offices in the building where he had been captured. Bowen, the Ranger boys, and Peter were there, and several company officials were on the way.

Little was being said; Bowen and the boys were getting their first really good look at the spy, and the redhead was returning the compliment. He was small, as they already knew, about five feet, two inches tall; he could not have weighed much over a hundred pounds. He was certainly younger than Dart. He was wearing a plain T-shirt, corduroy slacks, and sneakers.

The clothes were clean and neat, but obviously had been chosen to let him run, climb, or jump as might be needed. His face was a little pale, but no one could tell whether that' was his natural complexion or arose from fear at his present situation or pain from his damaged ankle. Bowen had asked whether it hurt the moment he saw the boy limping between Peter and Bart, but had received no answer. Seeing that the youngster was determined to say nothing, Bowen was glad enough to wait for the arrival of the company officers who had been summoned by telephone. It gave him a chance to plan his questions.

They arrived at the same time: Walter Ledder, manager of the plant, and Ray Deschenes, the engineer who had been in charge of the satellite construction.

"Good afternoon, Dr. Bowen," Ledder greeted him as the two entered the office. "Hello, boys. I see this is the young fellow Dr. Bowen mentioned to me some time ago. Have you learned anything about him yet?"

"Only that he doesn't intend that we shall learn anything," replied Bowen. "We hadn't really started to question him; we were waiting for you."

"I see. Well, we have not yet called the police, since you thought it would be better not to, but if he is doing us no good, there seems little point in keeping him on our hands."

"Who do you think you're scaring?" The young prisoner seemed suddenly to change his mind about silence. "You wouldn't bring the police, and it wouldn't bother me if you did. You didn't dare the other time you caught me." Bowen raised his eyebrows at this.

"That's an interesting viewpoint," he said. "I seem to recall saying that the police would be inconvenient, but I don't remember saying anything to suggest that I was afraid of them. What gives you the idea that we should be?"

"You know as well as I do. You're trying to be the first to get to the moon, so you can have it for yourselves."

"What gave you that idea?"

"I knew it when I was first told to watch you, and see if you had any ideas for letting people stand space flight."

"You seem to have a rather thoughtful boss. I don't suppose he let you listen to that tape you managed to get from the listening device at my house."

"Sure he did. I wondered why you let me get away so easy, but when I heard that, we knew you wanted us to hear it. You found the mike and then made up that talk so we'd think you were O.K. You must have known it was there, or you wouldn't have had these fellows waiting for me with cameras."

"Very good. Very good indeed. I take it, then, that your employer has told you that he is interested in preventing anyone from laying claim to the moon or any of the planets, and feels that the best way for him to do it is to get there first himself."

"No! He's not going himself; he just wants to know how you plan to do it, so he can report to the government and they can beat you to it."

"He's more foresighted than I thought—to tell you that. I suppose if has occurred to you that he might have put things backward; that we are really the ones trying to prevent private seizure of other worlds, and that he---"

"He isn't! I believe him; he's been pretty good to me all along when no one else was, and no one's going to talk like that about him while I'm listening!" The little spy leaped to his feet in rage as he practically shrieked this, but his ankle gave under him, and he fell back in the seat, breathless but still furious.

"I'm sorry," Bowen said gently. "If you are personally loyal to him, I hate to spoil your trust, and I certainly won't ask you to go back on him or betray him while you feel that way. Nevertheless, it is true that our plan is exactly what you say his is; we have been asked not only by our own government but several others to do just that, so as to prevent what could become an embarrassing situation from developing."

"I don't believe you!"

"Naturally not. There are a couple of points, however, which your argument has not made clear; perhaps you could explain them more fully. First of all, if it's your friend's idea that we made up that conversation whose record you took, why did we make any attempt at all to catch you and thereby show we knew your listening machine was there?"

For a moment the redhead made no answer.

"I suppose it was just so you could use this argument," he said at last, a trifle lamely. Then he brightened. "Besides, you were mad at the boys for trying to catch me; you said you just wanted them to get my picture."

"You're quibbling, and you know it. Even taking your picture would show we knew about the listener —you must be able to see that. That's just one point, though.

"I'm a little curious about this claim that we made up and acted out the conversation on the tape you got. If this friend of yours knows that we're trying to get the moon for ourselves, whom were we supposed to be fooling? If he is a government agent, as you imply, what good would sending him a record like that do us?"

"Well—I guess—you might have been trying to fool me, to get me on your side instead of his."

"We didn't even know you existed until we caught you getting the tape. We couldn't have, and if you had stopped to think for a moment you'd have realized it. If you'll give me just one sensible reason why we should have faked that conversation, I'll give you five dollars."

"You could afford more than that if you owned the moon."

"All right. All right. You're loyal, and I can't very well hold that against you. I still think, though, that a few minutes' clear thought about this matter will at least show you that you have no more real evidence against us than there is against your friend." The boys suspected that their uncle was getting a trifle impatient. "Just what would it take to convince you that I was speaking the truth, and that your friend was either lying or mistaken?"

"You couldn't do it!"

"Not even if it happens to be true?"

"It isn't!"

"That poses an interesting question." Bowen pondered for a minute or two. "It's a matter of just what we're to do with you. If we let you go, you'll trot right back to your nameless friend with whatever you've learned here, and there's one thing which I very much don't want made public yet. We can't, apparently, convince you of our honesty. We can't legally keep you."

"We can have him kept," cut in Ledder. "He was trespassing, and if he doesn't tell the police more than he's told us, they'd want to hold him for investigation —find his parents or guardians, and so on. If he did tell them more, the information might be quite helpful to us."

"That's a point," admitted Bowen. "How about it, young fellow; do you want us to turn you over to the police?"

"You can try that bluff all you want," the boy replied. "I know you won't dare do it. I've seen too much in this very building. I could prove you're trying to get into space."

"Of course we are! We've told you that already, and we aren't worried about who knows it!"

"Then why didn't you want to turn me over to the police earlier? I'll call your bluff, Mister; go right ahead."

Bowen realized that he had talked himself into a corner. He did not want it known that he was using teen-age boys as test pilots until the experiments were over, at least; it might be legal, but would certainly be unpopular with some people. He did not want to explain that fact to the captive, since it was possible that that was not one of the things the youngster had learned from his day's spying. He hesitated, and the redhead saw that he did.

"Got you, haven't I?" he crowed, and grinned around the company in a way that showed how completely he felt in charge of the situation.

Peter spoke up for the first time.

"Maybe this would help," he began. Everyone looked at him with surprise; it had been taken for granted by everyone present that the boys would not try to take part in this discussion. Ledder looked as though he were about to say something; then he glanced at Bowen and left matters up to him.

"Let's have it, Pete." Bowen was glad of the interruption, even if Ashburn's idea should turn out to be worthless.

"Our friend here, who dives over people's heads and doesn't seem to care whether he's right side up or upside down, thinks we're trying to get to the moon to claim it for ourselves. We think he and his friend are trying the same thing. He's been spying on us to see how we propose to go about it, since I suppose he's read the papers and knows that people can't stand weightlessness. Why don't we make everyone happy by taking him along and showing him?"

This suggestion had a mixed reaction. The Rangers and their uncle saw what was in Peter's mind, since he had referred to the redhead's tumbling skill; Ledder and Deschenes thought he was crazy, and the captive appeared to share their opinion.

"I see a couple of difficulties—" began Bowen.

"I know," Peter cut in. "But look. We don't care who knows all the details once the tests are done—right? We're going to the satellite station first for the tests, so our friend—I wish he'd give us a name, so I could be more polite—won't have to worry about our jumping the gun with a moon flight. If we haven't convinced him when we come back here after the tests, we're at least no worse off than we are now as regards his spilling the beans; in fact we're better off—either the plans work, and we're ahead of the others by however long it will take to train pilots, or they don't and it doesn't matter what is told to whom. He's better off because he knows more than he does now. If we do convince him that we're playing straight, of course, the problem is solved; he either forgets his 'friend' or induces him to help us, depending on whether that unknown gentleman has been lying to him or is honestly mistaken."

"You seem to have—" began Bowen, when the captive cut in with his favorite question.

"Who do you think you're fooling? You won't go anywhere near that satellite station; it's the Geographic project. If I take off with you, you'd dump me out somewhere."

"That would be pretty hard on us, if your friend knows where you are," pointed out Bowen. "What you think we're doing is not criminal, but murdering you most certainly is. In any case—"

"In any case, he's read in the papers about what happens to people in space, and doesn't want to go," cut in Peter. The redhead's face turned white, then almost as red as his hair.

"You walking dictionary! I want to go more than you ever wanted to read a new book! I've wanted to see the moon and Mars and Venus since I knew what they were. To you it's just something to own when you get there; I bet you don't even know there's a part of the moon we've never seen! I bet you don't know there's a place on the moon where the sun never sets! Oh, no! To you it's just a big ball of rock with maybe some uranium or thorium mines in it that you can make money from. You gawky talking machine, I'll go anywhere you go and do anything you do except read Einstein, and I'll get there faster and do it better. Why do you talk so much?"

"Even though you believe we'll throw you out on the way?" queried Bowen. He was not convinced of the worth of Peter's idea, but was delighted that a weak spot in the captive's personality had been found.

"I'll go, and if you can throw me out it will be the first time I haven't been able to take care of myself! Bring on your rocket."

"All right." Bowen's voice was quiet. "I'll take you for one reason only. Since we are going to the satellite, you will certainly realize that we've been telling the truth when we get there; when that happens we can settle matters more definitely. How about a name for you? I agree with Peter; calling you `Hey-you' isn't very polite."

The youngster grinned, though the grin was a trifle shaky. It seemed to be dawning on him that, like Bowen a few minutes earlier, he had talked himself into a spot.

"My name's Michael," he admitted. "We'll skip the other one for now. Most people call me Tumble, though." Bowen looked at him and nodded slowly.

"After that dive over the heads of two boys, both several inches taller than you, I'll go right along with that name," he said. "All right, let's get you measured for a space suit, Tumble."

THE PROBLEM OF TUMBLE

THERE was one thing that was very carefully not told to Tumble: the sort of tests which were to be made in space. It was possible, of course, that he had already figured out why boys as young as Peter and the Rangers were going along, but it was also possible that he had not, and Bowen did not intend to take chances on having that point leak out. The boys, therefore, were cautioned to say nothing whatever about the possibility that they would be the only space pilots on Earth if things turned out as was hoped.

Peter had added another reason for this. He suggested that if Tumble had no idea of the possibilities being tested, then his reaction to what actually happened might mean more than that of the boys who were all looking for one particular result. Even Ledder and Deschenes had joined Bowen in admitting that this was a good point, and Tumble was therefore given the same physical checkup as the other boys without being told that this was anything but the usual prelude to a rocket flight.

Some of the tests on Tumble bothered the Ranger boys almost as much as they interested the doctors who gave them. The Barany chair did not bother him at all; after sixty seconds of spinning nearly twice as rapidly as any of the other boys had, he stood up, wavered once, then fixed his eyes on the wall at the opposite end of the painted line and walked straight along it. Peter nodded as he saw this.

"Tell me, Tumble, did you feel dizzy when you got up, and just made up your mind to trust your eyes alone, or didn't you even feel dizzy?"

"Well—" Tumble seemed about to claim that he had not been bothered in the least, but remembered his first stagger in time—"it felt pretty bad in the stomach. Like you say, though, all you have to do is trust your eyes and forget the other feelings."

"That's what you do when you're tumbling, isn't it? I mean, when it's some stunt that has you spinning or tipped upside down? I've done some diving, but there you have everything set up before you leave the board, and it's over so fast that the balance question never seems to come up."

"It's mostly on trapezes that you have to depend on eyes and timing," replied Tumble. "The rest of the time there's no trouble with dizziness, unless maybe you're just showing off—doing cartwheels or flips down the whole length of a room, say." Peter nodded.

"Thanks. I'm not asking where you learned, but you certainly are pretty good at this business. Uncle Jim was right when he said you had a good name."

"He's not really your uncle, is he?"

"No, but I've known Dart and Bart for a while and don't have any real family of my own; I guess I've sort of inherited him. He's quite a fellow. You must have read about some of his mountain climbing."

"I don't remember. I don't read much, except books about the planets. We never—" He stopped, realizing that what he had been about to say might have contained more information than he meant to give.

Peter noticed the pause, but ignored it. He had ideas of his own concerning the best way to learn about Tumble, and direct prying into the other boy's affairs was not one of them; so Peter changed the subject the moment the redhead chopped off his sentence.

One of the things Peter liked about Tumble was his taste in reading. Somewhere in the past his imagination had been fired by something—a lecture, magazine article, television program, or perhaps just conversation —dealing with the other worlds of the solar system. From then on he had picked up every grain of information on the subject which fell his way, and gradually developed hopes which Peter understood perfectly, since he shared them. Tumble had not been acting when he burst out his feelings about visiting the moon; he had meant every word of it, and Peter had known it as he listened. At the moment, therefore, Peter Ashburn came closer than anyone else at the Niagara plant to trusting their prisoner.

For a prisoner he still was. The matter had been discussed after he agreed to fly with them, and the boy himself had admitted that he could not see any way in which they could trust him free. He refused to admit what he had learned while he was examining the shed in which he had been caught, even though he realized that such an admission might satisfy everyone that he had learned nothing dangerous. Even Bowen, annoyed at his own failure to learn anything from the boy, admired his honesty; Tumble had said flatly that if he were given the chance, he would be off in an instant to tell all he possibly could to his still nameless friend. There had been no choice but to confine him in the buildings where tests and training were carried on. He must have known that in doing this the plant operators and Bowen were putting themselves in what might become an awkward position with the law, since he could easily charge them with kidnapping, but he never mentioned it.

Bowen himself was wondering what steps the "friend" might be taking to learn what had become of his little agent. The mysterious person must have known that nothing violent would have been done, and perhaps thought that the Niagara police knew more than they were telling; but if he ever tried to find out from them, no news of the fact got back to Bowen. This was almost worse than if a group of lawyers had shown up demanding the boy. The suspense was beginning to get on Uncle Jim's nerves, as his nephews soon noticed.

"It's this trying to do my regular work, and wondering at the same time when the young devil is going to make a break for the fence," he remarked once. "I'd rather he tried it than kept me waiting."

"If he did, what good would it do?" asked Peter sensibly. Tumble at the moment was inside a partly constructed space suit while adjustments were being made to it, and Bowen and the boys had seized the chance to talk about the problem he represented. "If you caught him," Peter went on, "you'd be right back where you were before, since we can't put him on bread and water or something for trying to get away. If you didn't—well, that's just what you're worrying about."

"I know it. Thank goodness we'll be in space in another ten days; I don't know whether I could stand it much longer."

"You know," Bart said thoughtfully, "I'm not sure that he'd go even it we let him. Either he's a darned good actor, or he wants to make this trip even worse than I do; and that's saying a lot." Bowen looked at the other boys to see how they felt about this. Peter nodded agreement; Dart looked uncertain, seemed about to say something, but changed his mind.

"You may be right," Bowen said slowly, "but he's a capable young fellow, and it wouldn't surprise me if he were as good at acting as everything else. I know it's reasonable for him to be interested in traveling to the moon or Mars, but how do you tell whether he really is or not?"

"He certainly has read a lot about them, as he said," pointed out Peter, "but he's not a real scientist—at least, he doesn't have much idea how things were found out about the planets. He can tell you what the air of Mars is like and the temperature of the hot side of Mercury, and rattle off the names and distances of Saturn's moons. Remember his crack about the place on the moon where the sun never sets? I didn't believe him, but I looked it up, and there is such a place. Those aren't things he picked up in school, and I don't think he boned up on them just on the chance of being caught. I rather agree with Bait; he'd stay with us anyway for the flight."

"You may be right, but we don't dare count on it," replied Bowen. "Also, please don't relax in your job of watching him, just because you think he doesn't need watching. Remember there's another reason why he might be staying on his own hook; he's learning a lot. We don't care whether most of it gets out or not, but he doesn't believe that. I don't see how anyone, even as young as he, who looks at a newspaper can have been so thoroughly fooled. This company was mentioned as the makers of the satellite station; my name was used, and even my picture, quite a number of times; the whole story of the first flight was published, together with the statement that we were looking for public help. Yet he gives this yarn about his friend's being a government agent out to stop exploitation of the planets! It just doesn't fit in with the brains the kid seems to have."

"You think, then, that he's working for someone who plans to pull something fast in the way of space travel, and all that we've seen of him was an act, made up for cover in case he was captured?" asked Bart.

"I don't know what to think. Pete's quite right about his astronomy; it's hard to believe that he could have learned so much just to put on an act. Still, he may have fooled Pete too, now that I think of it. Pete, has he ever kept up a connected conversation on these things you mentioned, or does he just drop some remark now and then which has given you the impression that he knows a lot? I mean, someone could learn about the moons of Saturn and the temperature of Mercury and so on—just pick up a few dozen facts, perhaps, which he could scatter at useful times. You see what I mean?"

"Yes," replied Peter, "and you might be right. I hadn't thought of it that way. When he did say something like that I didn't keep up the discussion; I just remembered it so that I could look it up later to see if he were right."

"I see. In that case, it might be smart for someone—probably you'd be the logical one—to get him really involved in talk about his beloved planets."

"I bet he'll know what I'm doing."

"He probably will. Still, I don't see how that will hurt; if he really knows his business, he won't mind your finding out. If he doesn't he must know that he'd be caught out some day. Having it happen might stimulate him to try to get away, and that would at least end this miserable suspense."

"You mean you really want me to come out in the open and cross-examine him on what he knows of astronomy?"

"Well, no. You might as well try to be subtle. I'll tell you what—there's a telescope here at the plant. It's a regular astronomical instrument, with equatorial mounting and all that; they use it to measure the position of the satellite station, as a check on the radar bearings. It's a pretty good gadget, I believe. Why don't you and Tumble get together for a moon and planet gazing session? That would be natural enough for you. He couldn't refuse without stepping out of character, even if he wants to, and talking astronomy would certainly be natural under the circumstances. I'll see that you're given freedom to use the telescope when they're not making position checks with it." Bowen made a brief note in the tiny appointment book he usually carried.

"How about us?" asked Bart. "It seems to me that it would be just as much out of character for us not to be there as for Tumble to beg off."

"True enough. I can't be there, though; that would be going too far. I'll have to leave it up to you boys. I'll expect a report in the morning, Peter, on how genuine Tumble's astronomical knowledge is."

"Excuse me," said Peter, "but hadn't we better make sure there's something in the sky to look at before we make up the party? Is there an almanac or something around, or does anyone remember where the moon was last night?" The ensuing silence made it evident that no one did, so after a pause Peter suggested, "Well, then, I'll ask him anyway. If he knows what there is to see, it will tell us something."

All agreed to this, and the rest of the day was spent fitting space suits. Those of the Ranger boys were nearly finished, but Tumble's still had a long way to go. His size was bothering the designers seriously. Peter had no chance to ask him about using the telescope until nearly suppertime; when he did, the face under the mop of red hair lighted up in a way that made it very hard to believe that there was any acting involved.

"Sure!" he exclaimed. "I didn't know they had a telescope here. What can we see?"

"I don't know," replied Peter. "I haven't had a chance to look it up. There must be something, though. Of course, it won't be dark till pretty late; but—"

"But we can go see the telescope right after we eat, can't we? We'll have to learn how to use it, and anyway we should be able to see things before it's really dark." They went off to supper with that agreed, and as soon as the meal was finished the four boys headed for the small dome which contained the plant's observatory. There was no guard, and the door was unlocked.

Tumble was unbelievably excited; he had recognized Jupiter and Saturn in the sky, as well as the moon, and could hardly decide which to examine first. They finally settled on the moon. It was a day or two past first quarter, rather low in the southern sky; and after examination of the controls, Peter rather gingerly swung the twenty-inch Cassegrain toward it. Tumble followed the eyepiece around, almost dancing with excitement—he had, as he said, done a lot of reading, but had never had a chance to use a large telescope himself. He gave a cry as Peter, at the finder, steadied the instrument at the proper coordinates; the others could see the glow of the moon reflected from his eye as he peered into the big tube. He was talking, almost as though to himself.

"Golly! Just like the pictures! That must be Copernicus, right near the edge! and the Alps—that straight valley they always wonder about—and Plato and Anaxagoras and Shackleton—darn it, Pete, we can't see the north pole very well; I wanted to show you those mountains I was talking about—"

Peter forgot all about testing and began to enjoy himself.

THE POLARIS

UNCLE JIM heard the report on Tumble's reaction later that night, when the redhead and Dart had gone to their bunks. He nodded at the end.

"It looks very much as though you were right: he really is interested. However, we'll continue to keep an eye on him; goodness knows he could want to get into space and still be willing to do it with someone else."

"He couldn't do it nearly as soon, if his friend is in a state where he needs to spy on us," pointed out Bart.

"True. Well, I'll still be happier when we get off the earth with the young fellow. I wonder what he'll do when he finds we've been telling him the truth?"

"Stay around, I hope," replied Peter. "I like him. Besides, with what he knows about the planets, he ought to be good at exploring, if it turns out that we can do some looking around."

"Maybe. We'll soon know, anyway. The Polaris will lift a week from Friday, and we'll be at the satellite in a couple of hours after that."

"We? Are you going? I thought you couldn't go back into space!" Bart made the exclamations, and Peter's face showed that he was equally surprised.

"I'm going. I'm responsible for you boys, and you're not going to get so far that I can't keep a finger on your doings, believe me. I'll be able to stand the trip; they've arranged to use power all the way, as nearly as possible at one G, so the only times I'll be weightless will be at the half-time point when we reverse and while we're going from the Polaris into the station. I'll last through that—I guess." The boys did not fail to notice his expression as he made this statement, and looked at each other with some uneasiness.

"If you think you can stand it, why isn't it possible for you to do all this exploring yourself?" asked Bart.

"And if you're wrong, and lose your control during this turn you mention, what happens to the Polaris?" added Peter.

"To answer the second question first, the Polaris will be on automatic control the whole flight except for the last few seconds; during the contact with the satellite, the crew there will handle her by radio control. As for the other question, I only think I can stand this because it will be so brief—a few minutes at the most without normal weight. In any sort of exploring flight there would have to be maneuvering which could not be calculated completely in advance; that would mean changing power, and therefore changing weight over much longer times. That would be the situation which could leave a rocket with a helpless crew, in a place where assistance could not possibly reach them. Also, the gravity on other worlds would be wrong, and nothing could be done about it. No, Pete, your idea is still the only one which anyone here thinks has a chance of working."

"And I suppose they're pretty doubtful about that."

"Well, yes. But as you said some time ago, we can't be sure without trying. The two of you had better get to bed; you'll need to be in good shape for this trip, whether the idea works or not, and you'd better keep good sleeping hours. Come on—jump!"

"Better get some sleep yourself, Uncle!" retorted Bart as they left the room.

Bowen promised to do his best, but with the work remaining to be done in the next nine days, his best turned out to be a remarkably small amount of sleep. Even Tumble noticed it, when the explorer paused for a few minutes one morning to watch some tests being made on the Polaris' drive section. The boy was still uneasy about speaking directly to Bowen, but after the man had gone on he asked Peter about it.

"Say, Bookworm, isn't that Dr. Bowen looking pretty shot? I hope he's not going to be flying this thing, if he isn't in any better shape when we go."

"He won't be; he's not a pilot," replied Peter, "but you're right about the way he looks. He's working too hard for a man who's been sick."

"Why should he have much work to do? Everything is built, except some of the space suits. I should think they'd just be waiting."

Peter smiled, and looked at the younger boy.

"Never read much about airplanes, did you? There was one called the B-36, which had ten engines, and the things they had to check before every single flight filled a fair-sized book. That was after they'd built a lot of them and knew what they could do, too. The Polaris here has about four times as many miles of wiring in her electrical gadgets, and—"

"What do you mean, miles of wire? What do they need all that for? Isn't she just a rocket ship?"

"That's all. Just a rocket ship. With a Phoenix fusion engine loaded with electric and magnetic gadgets; at least four electric calculating machines; radios for long range and short range; special radios to talk to people in space suits; radio direction finders, radar scanners, television contact between pilot and power room; electric control for all the doors so they can be operated from either outside or inside or the pilot's station and —"

"All right, all right. Don't use the word 'electric' any more; I get you. I still don't see why Dr. Bowen has to work so hard, though. He's not the guy who builds and checks all that stuff."

"He works because we haven't built a lot of ships like the Polaris, so nobody really knows what they can or can't do and exactly what will happen to them under different conditions. Uncle Jim is the fellow who has to worry about things that may happen and figure out beforehand what to do about them. Would you like the job?" Tumble thought for a while, watching the busy engineers as he did so.

"Sure," he said suddenly. "If it's not engineering, what can happen? There's nothing out there to worry about. If the ship works all right, everything's fine. You can't run into anything, and anyone could figure out how much food and air and water you'll need."

Peter just managed to keep from laughing for a moment; then he grew very serious indeed.

"Even if you were right, Tumble, that nothing out there is something to worry about. Did you ever have your blood boil?"

"Well, I was pretty mad when you said I was afraid to go into space with you."

"I don't mean it that way. Come with me." Peter slid down from the cable reel on which he had been sitting. "There's something Uncle Jim doesn't know I've seen; I guess he didn't want us to see it, but maybe you'd better." He headed for the observatory building, but did not visit the telescope. A small room there was filled with reference books, and of course Peter had found them long since and spent some time browsing through them. He led the way directly to one of the shelves and took down an obviously old and much-read book. Tumble caught just a glimpse of the title—something like Principles of Aviation Medicine, which seemed rather uninteresting to him. Peter took only a few seconds to find the page he wanted, and showed it to the redhead. Tumble looked, his face a puzzled frown. "What's that? A fur-covered football?"

Peter shook his head, his face grimmer than Tumble had ever seen it.

"No. Read the description. It's a rabbit."

"A rabbit! It looks as though someone had pumped it full of air."

"Not air. Steam."

"You're crazy. What really did it?"

"What you were talking about a few minutes ago. Nothing."

"I don't get it."

"Ever hear of the way water boils at a lower temperature in high-altitude places like Santa Fe, where the air pressure is lower?"

"Sure. That's why it takes so long to boil eggs or potatoes; the boiling water isn't so hot."

"Right. Well, what happens if you go higher still?"

"I suppose the boiling point gets lower."

"It does. At about sixty-three thousand feet it gets down to the same temperature as your blood—and your blood is mostly water. What happens then?" Tumble blinked, looked at the picture once more, and gulped.

"I—I see."

"This is a very old book; it was written just about the time people were first building high-altitude airplanes. They didn't have pressurized cabins, and wanted to find out what would happen to the pilots at different heights. They did it by putting animals in a room and pumping the air out. That's why I said nothing did that to the rabbit. It's the same nothing that we'll run into in space."

"Seems like a dirty trick on the animals."

"It was quick, and I suppose that they had 'em under ether. Anyway, better a rabbit than a man. Now do you see the sort of thing that worries Uncle Jim? There are risks like that, and probably others that no one's thought of, and he feels responsible for Peter stopped with a jolt. He had been just on the point of letting out the fact that must not under any circumstances be learned by Tumble until he was safely away from the earth—supposing he didn't know it already. "—for the success of the whole thing, even if he isn't an engineer," he finished rather lamely. "Now do you want this job?"

Tumble's eyes went back to the picture. His freckles showed a little more clearly than usual.

"I guess I don't," he admitted. "Say, Pete, wasn't I supposed to get some more measurements for my space suit today? Maybe we'd better get over there; I wouldn't want 'em to feel rushed about anything."

"All right." Peter put the book back on its shelf and followed the younger boy from the room. He was rather pleased with himself; he'd made Tumble do some thinking. Then he began to wonder whether he might not have been overdoing it; after all, he didn't want to frighten the kid so badly that he'd back out of the trip.

"Pete, are you sure those suits can stand the vacuum?" Tumble asked as they fell into step. "I should think they'd just burst, like balloons that have been blown too far."

"No, there's no worry about that. The plastics they're made of are about four times as strong as the same thickness of steel, the engineers told me. The joints are so well made that it would take years for all the air to leak out. There are batteries to run the radios and the gadgets that renew the air you breathe, but as long as you're in sunlight the air renewers use that for power; even if you're in the dark for days and the batteries run down, there are spare oxygen tanks. They have temperature controls to keep you from freezing—well, like every other machine you see around here, they have anywhere from fifty to two or three hundred years of ideas worked into them. I couldn't begin to describe how they're made, let alone make one myself, and I'd be willing to bet no one else could either!"

"But how can anyone make them, then?" Tumble sounded doubtful, but at least seemed to have stopped worrying.

"One person doesn't, any more than one person makes a car or an airplane—or the Polaris." That set the redhead off an another slant.

"Say," he said, "I thought that ship was a rocket."

"She is."

"Then where does the gas squirt out? Every rocket I've ever seen pictures of had a big hole in the stern. The Polaris just has a big flat block of metal."

"The holes are there, only they're too small to see—about five thousand of them to every square inch, each one running straight through the block for about eight feet. The water that goes into the holes at the top is picked up and pushed out by forces something like magnetism, so it squirts away at thousands of times the speed any other rocket ever managed. That's why the Polaris and the other ships with this motor don't need to be nearly all fuel, the way the earlier ones were."

"I don't get it."

And, although Peter was a fairly good teacher, Tumble was a long, long time understanding all that made a Phoenix rocket work. He certainly didn't on the night when all the boys were ordered to get to bed early, since they would have to be up before three the following day to get ready for the flight.

No one is really awake at that hour of the morning, and not even the excitement the boys naturally felt as they got into their space suits, checked them as they had been taught, and accompanied the others out to the ship was enough to make them really alert until they got aboard.

Bowen and the pilot went all the way up to the nose, over two hundred feet from the ground. The boys and the two other men who were going on duty at the station began strapping themselves in the harness provided in the next room down, although there was no particular reason to expect any heavy jolts.

The man in charge of the passenger compartment plugged a line from his space suit into a phone connection on the wall, and reported that everyone there was ready to go. The pilot's voice came back.

"All right. We still have eight minutes before we lift. Does everyone down there have his phone plugged in?" The boys had not, and the man quickly showed them what to do—no one had told them about the phone connections in the Polaris, though they had been talking to each other over the radios in the suits.

In the control room, the pilot carefully checked the punched tape which was feeding instructions to the automatic control. Several times he checked it against the time signals coming from Washington; each time it proved correct.

"Stand by to lift!" he called suddenly, as a solid row of punches extending entirely across the tape disappeared into the mouth of the autopilot. Everyone tensed; they trusted the engineers, but mistakes were sometimes made—

Those in the blockhouse outside saw the air under the Polaris suddenly glow a dazzling white. The radiance spread to the concrete, which started to crumble and spall away; in the few seconds it took to raise the ship a hundred yards, a foot-deep hole was eroded in the surface. Then the ground began to cool, and the watchers shifted their eyes to follow the great metal bullet.

It was rising with apparent slowness, the air under it glowing as though a giant searchlight were shining from its base. A wash of superheated gas struck the blockhouse. The whole area was humming in tune with the roar of the ultrafast gas column jetting from the Polaris' drive unit. Very gradually the sound died away, and the glow faded to a spark; finally that, too, vanished in the early morning sky.

THE LONG FALL

THE boys had read their share of books dealing with space travel, and had seen more than one motion picture dealing with the same subject. These had all been written before the Phoenix motor was developed, and in spite of their knowledge everyone but Peter rather expected to feel himself dragging down on his harness and the blood rushing from his head under the ship's acceleration.

This did not happen; the tremendous accelerations mentioned in the stories were needed with chemical-powered rockets which had to get their speed before the fuel gave out, but the Polaris lifted herself almost gently into the sky. At no time during the first part of the flight did the weight of the people and objects aboard get more than ten percent above normal, and after the first three minutes of lift the pilot permitted his passengers to get out of their harnesses and move around freely.

The boys naturally headed for the few windows the ship possessed.

There was much to see. The sun had not risen at Niagara when the Polaris lifted, but it was visible now, glaring in a midnight-black sky. Below it a narrow crescent, blurred and hazy, marked all that could be seen of the earth. No details showed through the blanket of atmosphere except a single spot of brilliant light. This was the reflection of the sun in the surface of Lake Erie, and as they watched, it faded and disappeared. The Polaris was climbing at an ever-increasing rate, her automatic controls tilting her course toward the east and south, so that the lake no longer lay between her and the sun. At the same time the crescent grew broader, and as the rocket tilted they could look straight down and see vague details through the atmosphere.

It was Tumble who first noticed that the earth was no longer below them—that "down" was still toward the floor on which they were standing, while the world seemed to have swung a trifle to the side. It was just possible to see the outline of Erie and judge where Niagara must be even though it was not yet in sunlight, and it was no longer straight behind them. Peter was still trying to explain this to Tumble when a call from Dart interrupted them.

The Ranger boys had moved to the opposite window, and the younger one's loud reaction to what they saw brought the others hurrying over with the problem of net acceleration still unsettled. They did not blame Dart for his excitement; for although they had all seen a night sky, they had never imagined one such as they glimpsed through this port.

The sun, on the far side of the rocket, might as well not have existed. The Polaris was far above any measurable traces of Earth's air, and the scattered sunlight which hides the stars from sight in the daytime was absent. The stars did not wink at the boys; they stared, forming a peppering of steady points of light on the infinitely deep background of blackness; among them, very high above the hazy arc of darkness, which was the night side of the earth, hung the moon. It was now well past full; the raggedness of the western side could be seen even without a telescope, and the great dark plains which have made the "man in the moon" to generations of Earthbound children were clear as the eyes in a skull. Tumble stared in rapt silence, and the others were almost as awe-struck.

"Why is it off to the side?" asked the redhead finally. "Shouldn't we be heading straight to it?"

"No, for two reasons," replied Peter. "One is that we aren't going there—yet. The other is that even if we were, we could never follow a straight-line course in space; it's moving, and we'd have to head for the place it would be when we were to get there."

"I'll believe the second of those remarks," was the answer. There was nothing more said; everyone continued to look at the sky.

The stars were unbelievable, and the planets they had seen in the telescope were there too, though at first Venus was too nearly straight ahead to be seen. As the rocket tilted farther, however, the cloudy planet swam into view through the port they were using. Its appearance brought an awe-struck whistle from one of the men, and Tumble and Dart were both sure that they could see its crescent form with the naked eye. Peter and Bart doubted whether this could be, but even they found they could see three of Jupiter's moons. Peter was annoyed with himself for failing to find out before takeoff which of the satellites would be visible, and tried to figure out which the missing one must be from the motions he and the others had observed through the telescope on the previous few nights.

He was still at it when they were interrupted by Bowen's voice from the control room.

"Start getting back in your harnesses, boys. I'm coming down to your deck."

"What's up?" asked Bart.

"We'll be turning over in six minutes, and you'd better be tied down by then. We'll have to stop accelerating." He said no more, but three of the boys knew what he had left unsaid. So did the men, for they were losing no time at the job of strapping themselves once more at their take-off stations. Tumble alone was at a loss, and as was coming to be his custom, he asked Peter to explain what was going on.

"We've been picking up speed all along," was the reply, "and are now going very much faster than the station; we have to swing the ship so that the tubes point the other way, and use them for slowing down."

"I see. You pick up speed for half the journey, and get rid of it for the other half."

"It's not quite that simple; we didn't pick up speed as fast as we'll lose it, because the earth's gravity was fighting us. Besides, we don't lose all our speed, because the satellite is doing something like four miles a second, and we have to get in touch with it." Tumble thought for a moment.

"Then, I should think we'd go more than halfway before this turning over business was needed?"

"That's right, this time. Going back to the earth it would be different."

"I see." Tumble said no more, but did a great deal of thinking. Big as the moon looked with no air to cut off its light, even he could see that they had not come anything like halfway to it. Maybe these people had been telling the truth—but that was silly, he told himself. Lerch would never have lied to him.

"Why do we need to strap in?" he asked at this point in his thoughts.

"Because while we're turning over, the main drive will be off; and until it goes on again, we'll be weightless," Peter stated. He did not know how much Tumble knew of the effects of free fall—certainly plenty had been written in the papers since the troubles of the first flight had been made public, but Tumble didn't seem to believe all he read in the papers.

As the moment when Peter's idea would receive its first trial drew near, his heart was thudding a good deal faster than usual, and he could feel a damp trickle of perspiration on his forehead. He could not see the faces of his friends very clearly through their helmets, but Dart was quieter than usual as he attended to his harness, and his brother made a half-checked motion toward his head as though he had forgotten for a moment that he could not wipe his brow while the helmet was in place.

The news did not seem to bother Tumble. Even the arrival of Bowen from the deck above, and his care in placing himself where he could watch the clock set into one wall, did not bring forth any remark from the little spy, but the others could read a great deal into his silence.

"How long?" asked Bart.

"Thirty-five seconds, on automatic," replied Bowen. "The side jets could whip her around in five, on manual handling, but it would take a good deal longer for a pilot to head her exactly right; besides."

"I see." Bart said no more, and they all waited as the second hand swept again and again around the dial before them. None of the boys had noted the time when Bowen had first called down, so they were not sure just when the power was to go; but they learned. Bowen himself told them, in a voice that suggested that the words were being dragged from his lips against his will.

"Thirty more seconds—fifteen—ten—five—"

And someone cut the rope.

That was the way Tumble described it later. He had not known what to expect, in spite of the newspapers. He was, of course, used to the sensation of falling; the number of hours he had spent on flying rings, trapeze, and trampoline took care of that. The feeling, however, had never lasted so long, and after perhaps five seconds he gasped, "How long before we hit the ground?"

"We don't." It was Peter who answered, and he was sure ever afterward that Tumble's question had been the difference between success and failure of his whole idea.

For he had known what to expect. He, too, had known the sensation of falling, experienced time and time again between diving board and water. He had been telling himself that of course the ship would be falling, but that with her velocity she could never strike the earth at all, nor any other thing in space until long after everyone aboard had died of old age. In spite of his knowledge and what he had tried to tell himself, something had gone wrong. He knew the ship was traveling upward, in spite of his sensations—but which way was up? There was a ceiling—that should be above, though it didn't feel that way. For a moment he almost steadied; and then he saw the earth through one of the ports. His mind knew that earthward wasn't really down any more, but his sensations didn't agree. His eyes were telling him two different stories; his sense of balance was telling him nothing—or was it everything? His muscles were starting to tremble in a way that an airplane pilot who had suffered from vertigo would have recognized, and he had almost lost control of himself—when Tumble asked his question.

"We don't." Those words left Peter's lips almost without his thinking—they were the ones he had been saying to himself in answer to the very same question that the redhead had asked. The very act of speaking jerked his attention back from the crazy-quilt of sensations that were coming from eyes, muscles, and balance organs, and he was suddenly himself again. "We're heading up, still." These words were carefully chosen; he could think, once more. "We're going so fast that the earth's gravity could never pull us back, and it would be years before we could hit anything else. It's just a long, long dive, Tumble; take it easy. We'll have weight again in ten seconds." His eyes had focused on the clock, and he very carefully avoided looking at anything else. At least, the clock dial had a top to it.

Tumble did not answer, and the heavy breathing that came over the radios certainly did not belong to him alone. Others were afraid, too, and Peter did not blame them. His own stomach felt—

All right. Weight came back, along the hum of the drive, so suddenly that the knees of everyone in the room gave under the load. Tumble sagged just a little. Everyone else dropped as far as the safety harness would allow. The boys came back to their feet at once and began unfastening their straps without waiting for orders or permission; the men did not. Bart was the first to notice this.

"Uncle Jim! Are you all right?" Wrenching furiously, he got the rest of his harness off and leaped across the floor to his uncle. A shaky voice reassured them.

"Not exactly all right, but I will be. It—it doesn't get any better with practice, as I said. See about the others, will you? I don't want to stand up for a few moments; my sense of balance has gone again, I'm afraid."

The boys obeyed him, in grim silence. The other men were in about the same condition as Bowen; but all were able to stand up again after a few minutes' rest, and Dart, who had gone up to the control compartment, reported that the pilot was also recovering.

Bart had muscle cramps in arms and legs; he had held on to his self-control by sheer determination, with every muscle so tense that it hurt. His brother had felt about the same as Tumble, but had got through the worst by concentrating on Peter's words as he tried to explain what was going on. All four of the boys had come through far better than the men, and three of them were aching to get together where they could discuss the matter in private. Tumble felt no need for privacy; he told of his sensation at great length, without caring much whether anyone listened.

"You know, it's just as well I didn't eat much breakfast this morning," he remarked. "That long fall is rough on the stomach. Takes a bit of getting used to, I guess. Pete, did you ever try a dive as high as that one?"

Bowen snapped off his radio for the time being. His stomach was in no condition to hear the whole thing talked over again. He had never been seasick or airsick, but free fall was quite another matter. He began, with some pain, to plan just how he would tell the boys about the job that awaited them in another twenty minutes.

TUMBLE TEACHES

"IT'S over for now, anyway," remarked Peter. "I guess it's kind of lucky the ship was on automatic control just then."

"Can that tape take it right up to the satellite?" asked Tumble. The question came so naturally that no one thought to be surprised for several seconds; then they realized that this was the first time he had been willing to admit that the Polaris might be going anywhere but to the moon.

"No, it can't," Bowen replied, without making any comment on the redhead's apparent change of heart. "It will bring us close, and match our speed to theirs; then we turn over the controls to them, and they bring us in by radio."

"What happens to our weight then?"

"That—that's a trifle hard to say." The brothers listened closely; they had never heard their uncle use quite that tone before. "Exactly what maneuvers this ship will have to take can't be told now; but—"

"But we can't possibly stop exactly where we want," finished Peter, "and that means we'll not only be weightless some of the time, but will have our weight changing both in amount and direction while the ship is worked into contact. Isn't that right?"

"It is." Bowen's voice was hardly louder than a whisper.

"And half a minute without weight just now almost ruined you, and didn't do anyone else much good. How are you going to stand it?"

There was a pause of several seconds, and the answer was the last that the boys expected to hear.

"I'm not."

"But—" Bart and Dart started to cry out with the same voice.

"I'm not going to be able to stand it, and I was pretty sure I couldn't when we took off. The pilot is the same; he was on the earlier trip, and suffered as much as I did. Robbins and Derlen, here, may be able to, but it's not certain. Therefore each of us has, clipped to the mouthpiece of the drinking tube inside his helmet, a pill that will put him to sleep for an hour. The pilot and I will take ours just before the power goes off next time; Robbins and Derlen will take theirs whenever they feel that things are getting too much for them."

"But we don't have any pills!" It was Dart who made this protest.

"I know. Someone has to stay awake; it may have been selfish of us, but we decided that you young people were the most likely to be able to take it—as Pete has been hoping all along.

"It will be your job, boys, to see that we get into the station. The ship will be brought into its berth, which is at the center of the station where there is no weight; therefore none of the crew there can come to help us out. You will have to bring us out through our air lock, into the one at the berth, and carry us down to where there is enough weight for the others to meet you. I'm sorry to spring it on you like this, but I didn't want to tell you before. Until a few minutes ago, I was hoping that I wouldn't have to take my pill."

"I see." Bart spoke these words almost absently, as though he were thinking of something else; the other boys were silent. Bowen tried to smile, though his face could hardly be seen inside the helmet, as he added one more remark.

"At least, this will be the first and maybe the best test of the whole plan, eh, Peter?"

This remark caught Tumble's attention; and without thinking how such a question might be taken he blurted out, "What do you mean? You really did have an idea all the time, even if you were asking for more in the papers?"

"We did. Peter, it was yours; give him the whole story. He can hardly tell his friend now, and he certainly has a right to know anyway. It will kill the time until Pill-minute, anyway."

Peter obeyed, and the redhead listened without a single interruption. When Peter stopped talking, Tumble walked over to the nearest port and stood still, looking silently out into the star-speckled blackness; he remained that way for several minutes.

"All right," he spoke at last. "You make it sound pretty straight. I still don't know what to think, though. My friend has been pretty decent to me for a long time, and I can't seem to believe that he'd lie to me the way he must have if you're right. Let me think a while longer. After we get to the satellite, I'll decide one way or the other."

"That's fine, except for one thing," replied Bowen.

"What's that?"

"Don't feel you're being hurried. I don't care if you wait until we're back on Earth, or even later, to decide. I like you, and hope you come to see the truth; but I don't want you to take sides until you're really sure of the facts." Tumble made no comment to this, and no more was said for the few minutes that remained before the pilot called down.

"Two minutes left on the tape. All taking pills, strap in!"

The boys responded to this by rushing to the ports in the hope of getting a glimpse of the satellite station, but it was still so nearly straight ahead—according to the way they were traveling; actually the stern of the ship was pointing at it—that it could not be seen. The men had known this, and had not even tried to look—or perhaps they were too concerned with what was about to happen.

Bowen was resuming his harness, and the boys remembered that he had said the pilot was also going to go to sleep. The other two men were strapping in, but at the questioning looks of the boys Robbins said that they hoped to stay awake.

"It wasn't fun, but Dr. Derlen and I will make one more try. We're fastening down so that if we do lose control and have to swallow the pills, you fellows won't have to chase us all over the room in order to tow us to the station. We'll let you know, or at least try to, if we can't make it by ourselves."

The seconds passed, and the tension grew. Twice more the pilot spoke.

"We're on their radar." Another pause; then, "Thirty seconds to the end of the tape!"

Bowen calmly swallowed his pill, and collapsed in his harness without a sound. Above, the pilot must have done the same; and the tension began to mount swiftly in the compartment. The boys stayed by the windows, looking for the first sign of the satellite. Robbins and Derlen watched them, their fists tightening uncontrollably as the final seconds of powered flight ticked by.

Peter saw the station at almost the same instant the power was cut, and to his own great surprise found himself able to examine it in spite of the endless-fall feeling that immediately swept over him. It looked like a great, thin drum, spinning about three times a minute. At the center of the circular face which was turned toward the Polaris was something that looked like a huge gun; Peter knew that it was a telescope, placed where the spinning of the station would not put a load on its mounting. The whole structure was five hundred feet in diameter, and almost a hundred and fifty thick.

"That's what was in the papers, all right!" He heard Tumble's voice over the radio, and discovered the redhead beside him. He must have crossed from his own port since the weight went off—a 'feat which Peter suddenly realized he would not like to attempt himself. The very thought of letting go of the strap beside the port was unpleasant. Before he could consider this any farther, however, Tumble went on, "Why is it turning like that?"

"To give a feeling of weight to the men inside," replied Peter. "Did you ever swing a bucket of water around your head, without having it spill? It's the same idea there. 'Up' to the folks in the station is toward the center, and their weight is less the closer to the center they get. That's why Uncle Jim said we'd have to bring him and the pilot down quite a way before we could get any help."

"I don't see that."

"Well, I suppose they'll dock the Polaris at the center, rather than try to have it catch up with the rim. That would be pretty hard, and I suppose it would throw the station off balance, besides."

"Do they pull that gun out of the way for us, or fasten us on beside it, or what? And where do we get inside?"

"I don't know; I haven't been here either, remember."

Tumble's question was quickly answered, however. Some of the motors of the Polaris began to function again, but this time not steadily. "Down" changed with startling speed; at the first jolt of power, Tumble snatched frantically at the strap to which Peter was holding, for the two suddenly found that they were at the top of the compartment. There was no trouble holding on, however; they developed only a few pounds of weight, and that vanished again in a few seconds. Now, however, the station appeared to be moving; and very gradually it seemed to turn until from a full view of its circular face it was quarter-on. Another brief jolt of power followed, and changed their course—even Tumble realized that it was the Polaris which was actually doing the moving—and carried them past the edge of the great drum until they could see the other face. It was the weightlessness after this shove which proved too much for Robbins; he gasped, "Sorry, boys," and became silent, his limp form drifting freely in the straps while coasting and sagging in whatever direction happened to be "down" when power was applied.

Two more changes of course set the rocket drifting straight toward the center of the drum. On this side 120 there was no telescope, but a framework quite obviously meant to receive the rocket; under the guidance of the unseen operator in the station, the Polaris drifted neatly into this scaffolding and stopped with a solid thud which told of either magnets or mechanical clamps securing a grip on her skin. At the same instant a twenty-foot circle of metal swung outward from the hull of the station, showing where entry could be made. It was only a problem of getting there.

Peter found himself still reluctant to let go of the strap, though his mind told him that he couldn't possibly fall. Bart and Dart were in the same situation, not quite afraid in their minds but with their bodies very unhappy about their sensations. Dr. Derlen was still conscious, but that was about all. Tumble was the only one who seemed both happy and in fairly good control of himself. Without saying anything, he suddenly let go of the strap he had been sharing with Peter, braced his feet against the wall, and pushed.

His space-suited form sailed across the compartment and struck the opposite wall just where it met the bulkhead separating the chamber from the control room.

"Darn! It's hard to aim!" he exclaimed. "I was trying to hit the port. Come on, Dart; let's see you do better."

With an effort, Dart let go of his strap. Before he could bring himself to push off toward a port, however, he had drifted out of contact with what had been the floor; a wild kick at it, when he realized what was happening, served only to send him against the same bulkhead as Tumble, though nowhere near the redhead.

"I win," the latter practically crowed. "Here, watch this. Right beside you, Pete!" He shoved off again as he spoke, and this time brought up just where he intended, clutching the strap he had released a few moments before.

"Come on; there's nothing to it. It's just like you said a while back, Pete; forget what you feel like, and don't believe anything but your eyes. It's like a good high bounce on a trampoline—though I've never stayed up this long yet. Push off; I'll pull you down if you start to float away!"

This remark stung the pride of the Ranger brothers, and they both began to try leaping, ignoring the chance to ask Tumble what he meant by "down." Neither one was able to control his aim for some time, but gradually they caught on, and after a while were able to reach any point in the compartment with a single dive. Peter, however, remained at his window.

"What's the matter, Pete?" asked Bart, half mockingly. "Glued to the port? No one will be coming out to meet us, you know."

"I know. They'll probably be wondering why we haven't come in, too."

"Well, then, let's get going. We can handle ourselves, without weight well enough to get the others in okay. Come on."

Peter knew Bart was right, but still found it hard to let go of the strap. He managed it, however, and doing his best to judge his line of flight, pushed off toward the spot where Bowen was floating. He didn't expect to enjoy it, but neither did he foresee what actually happened.

He didn't travel straight, which was to be expected, but what was much worse, he whirled. For three age-long seconds he was spinning in the emptiness of the room, with space suits, ports, walls, and the door into the control room all circling about him. Then he struck the far wall, clutched frantically at a nearby strap, and managed to stop himself, but it was several minutes before he could control his breathing again.

The brothers were laughing, but Tumble was not. When Peter could see straight again, he found the redhead beside him, speaking slowly and carefully.

"Hold it, Pete. None of us has tried to cartwheel yet; you were a little hasty with that. Now, fix your eyes on the place you want to go—say that port beside Dr. Bowen. Now, keeping hold of the strap, pull your feet up so that they're between you and the wall, and your head is between them and the port—that's it—now let go and push off!"

Almost without realizing it Peter did as he was told. This time he did not spin, though he did not hit very close to the port at which he was aiming. The main thing was that this time the sickening fear which had swept over him during the first dive did not recur. Later he realized how big a favor Tumble had done him in making him dive again right after his first failure. Twice more he tried, each time improving, and finally the redhead breathed a sigh of relief.

"You're all. Tight now. Let's see if Dr. Derlen can make it."

Tumble may have been feeling that he was a superior teacher; if so, the idea was quickly driven from his mind. Derlen did make an honest attempt, it is true; he released his harness, hoping that his space suit would hide his trembling from the boys. However, the instant he pushed off his self-control went. He gave a single shriek as the lack of support added itself to the endless fall sensation, and swallowed his pill before reaching the other wall. He had just time to admit it before he lost consciousness.

Tumble whistled gently.

"That gives us one man apiece to tow," he said thoughtfully. "Who knows how to open the air locks? We'd better get these men into the station."

The sudden knowledge of their responsibility sobered all the boys, and with no more joking at Peter they each took hold of one of the drifting figures—Dart bringing the pilot from the control room—and towed them toward the nearest air lock. This was not the one by which they had entered, but was located much closer to the nose of the Polaris; two minutes later they had drifted easily through the still open door of the space station. Someone must have been watching, for as the last space suit floated through, the door closed silently behind them.

TUMBLE LEARNS

PETER was still not sure how he had made the jump to the station, with the helpless figure of Derlen in tow. Weightlessness was bad enough inside the walls of the Polaris; outside them it was far, far worse. Inside, one could tell himself that he might indeed be falling but there were only a few yards to fall; outside, that comforting fiction was impossible. A cave man might have been able to convince himself that the sparkling blackness around him was only just out of reach and that a fall to it would be harmless, but not Peter, who had known the distance between Earth and its moon since he was eight years old.

He had almost given up when he first emerged from the rocket's air lock; he had had to back inside once more, fix his eyes on the entrance to the station, and start his dive from a point where he could not see the emptiness all around him. Keeping his gaze fixed on his target, he had made the crossing without actually crying out, but he was not looking forward to the next time.

Safely inside the great air lock of the station, with the outer door closed and air hissing softly into the chamber, he was able to forget that trouble for the moment. He was still weightless, falling with the station along its endless path around the earth, but he was actually getting used to that. He had stopped worrying about whether his idea would work; he knew already that it would. At least, he would have said so to anyone who asked.

The boys had no way to measure the pressure of the air in the lock, but they knew that it must have reached station normal when another door opened before them. It led into a room almost as large as the lock itself, and equally empty. Like the lock, its wall was studded with metal grips, and without waiting to discuss the matter the boys each dived through the door, carrying the helpless men with them. There were no signs to point the way, but all directions led down; so they simply continued the way they had started, through rooms and corridors all without furniture or equipment. Even dust was lacking here.

Soon they were no longer able to dive straight for a target; they were missing it, or sometimes reaching it too soon. They could not yet feel any weight to speak of in their own bodies, but the ones they were towing became harder and harder to hold back. Then Bart discovered he could stand—that he had weight enough to keep his feet pressed against one wall, which they henceforth thought of as the floor. From then on they were more careful about diving, and at last they had to climb, using the wall grips as rungs on a long ladder. Then the space-suited men became too heavy for one of them to carry. Still they had met no one, and heard nothing in their suit radios except each other's voices.

"You'd think they'd have started to put in stairs by this level," remarked Bart at last, as he eased his uncle to the floor and settled down to rest briefly himself. "They certainly knew what weight would be at the different parts of this place."

"We must have nearly a third of our regular weight right now," agreed Peter.

"Why doesn't one of us stay with the men, and the others scatter out to look either for a better way down or for the people who are here?" asked Tumble sensibly. No one could find any objection to this, and Dart was selected to remain. Bart went on down, while Peter and Tumble hunted for an elevator or stairway on the same level. To the embarrassment of the whole group, it turned out that there were several elevators so close that they should have found them long before if one of them had thought to look; they located two so quickly that Bart was still near enough to be called back. The helpless men were bundled into one of them, and Bart pressed the lowest button in the row on one wall. The door slid shut, and the cage started downward.

The start of a descending elevator is the closest approach to weightlessness the average person ever experiences. The, boys knew that, and they expected that they would scarcely notice it after their recent experiences. However, they were wrong. It was a slow elevator, but as it started to leave their feet behind, all four of the boys suddenly felt as though their stomachs were trying to get back to the Polaris. Peter clutched at a rail on the wall, apparently meant for a hand-hold; the brothers seized each other; and even Tumble only partly stopped his impulse to find support. The sensation was over as quickly as it had come, but it sobered the boys. Apparently they had not completely solved the problems of space sickness yet.

It took several minutes to reach the bottom, but when they arrived their troubles were over for the time being. Virtually the whole crew of the station was waiting at the elevator. They had seen the party cross from the Polaris, but had not known where they were after the inner door of the air lock had been opened. The station was not full of television equipment, not being a prison, and it had not been possible to talk to the newcomers on their suit radios since the metal walls cut off the radio waves. None of the satellite crew knew that four of the visitors were unconscious, since the boys had looked just as helpless as the men when they dived across from the rocket; and as the minutes passed with no one appearing and no elevator working, the crew began to fear that all the newcomers had succumbed to the effects of weightlessness in the upper levels. Plans were being suggested for rescue methods when the indicator showed that one of the elevators was moving.

The men of the station were more than surprised to find that half the newcomers were young boys, but they did not waste time discussing the matter. A few words explained the condition of the grown men, who were immediately escorted to the infirmary. The drug they had taken did not take too long to wear off, and presently Bowen was giving the whole story—except for Tumble's peculiar status—to the assembled crew of the satellite.

The men were dubious, for the most part. They had all tried their best to get used to the sensation of endless fall; they had ventured, singly and together, up to the higher levels of the station; but they had all failed, in spite of the firmest will power and strongest determination any of them could muster. A man simply can't ignore twenty-five to forty years of getting used to weight; most of them doubted that anyone could overcome even fifteen or sixteen years of it.

They realized that the boys had done quite well during and just after the flight of the Polaris, but most of them had had similar spells when they thought they were getting accustomed to it. Always, sooner or later, their emotions had taken control away from their minds. They nodded grimly—and sympathetically—when the boys admitted their experience in the elevator.

Nevertheless, no one suggested that the trial should not be made. Every man of them told of his own attempts in detail, in the hope that some idea which had failed for him might work for the younger people. Then they were given the freedom of the station, told to go where they liked, and try the low-weight levels whenever they wanted.

They found that they weren't quite as eager to go back up there as they had expected to be, but none of them wanted to admit it, so they went. In fact, they spent most of the next several days on the higher decks. They learned for themselves some of the things the men had told them, but which they had not believed—that even when a person thought he had learned to take the "long fall," the sensations would suddenly come back and steal away his control. They began to understand why the men had all given up the task as hopeless, but they themselves kept on.

The boys found that if they could keep their minds on some definite job, they could forget their sensations for a time. That was apparently why they had been able to do so well during the docking of the Polaris, and why they had suffered in the elevator with the end of the job in sight. They found that they could play children's games like hide-and-seek, or tag, or follow-the-leader, all the way from the edge of the station, where weight was normal, to the center and back again, but that the game had better end at normal weight. The let-down when one of the games was finished was almost sure to leave them all dizzy and helpless if it happened on a high deck.

The men advised, time and again, that they give up, but each time the suggestion was made, something would come to the boys' minds. With Tumble, it was the thought of seeing his beloved planets; with Peter, a mixture of curiosity like Tumble's and sheer stubbornness—the idea was his, and he was not going to give it up this easily. None of them found the effects growing worse with time, as the men had; this fact encouraged them when everything else failed.

So it went; gradually, in spite of what the men had predicted, some gains began to show. First an hour and then half a day and then a whole day passed without any of them succumbing to the terror of the long fall; finally Tumble performed an experiment which Bowen would have forbidden had he known about it in time. The boy went up to the center of the station late at night—they kept Niagara time on board—and deliberately went to sleep there.

It was sleeping in free fall which had originally cost Bowen his sense of balance; that brief but frightful instant just after he woke up and before he could recognize what was happening had been no time to be weightless. It might have killed him—almost certainly would have if anything had been wrong with his heart. He did not know about Tumble's experiment until too late to stop it, and he himself did not sleep at all that night. When the redhead appeared in the "morning" not only in control of himself but refreshed, Bowen hardly knew what to think, but he knew what to do. He turned to the station chief, Dr. Wetzel.

"Let's break out those scout rockets. I've seen enough." Wetzel looked thoughtful, eyeing Tumble, then Bowen, and then the other boys, who were waiting with an impatience that threatened to be as hard on their control as free fall.

"All right," he said abruptly. "We can't be worse off than we are. I like the kids, but if you think they can get away with it—"

"We're controlling the rockets and can get them back before anything drastic happens. As far as I'm concerned, the main idea has proved good."

The rockets were stowed in berths inside the station but located at the rim, since they had been designed partly as emergency craft. Even at the time the station had been built, there had been some worry about the effects of weightlessness. Wetzel led the way to one of these berths, and the party inspected the tiny craft inside.

It was far smaller than the Polaris. It was about thirty-five feet long and eight in diameter; three of the boys recognized with pleasure the original of the mockups in which they had practiced at Niagara. About half its length was taken up with drive unit, fuel tanks, and control and living machinery; the rest was divided into a pilot compartment in the nose and an even more cramped sleeping and eating room behind. It could be operated by one person, but could carry several if they did not mind the crowding.

"Are you going to send them out one at a time?" asked Wetzel.

"You're equipped to handle more than that by radio, aren't you?" countered Bowen.

"Certainly. We can control all ten, if you like; I thought you might prefer to concentrate on one at a time, that's all."

"That might be a good idea, but with a separate controller on each one to keep the boys out of trouble we should be safe enough, and training will go much faster. We'll handle them all at once."

"All right, we'll preflight four of them. I'll get the men on it right away." The commander turned to the boys. "These machines are all alike as far as I'm concerned, but maybe you have preferences. Pick out the ones you like, and we'll use those." Then he was gone, back toward the living quarters to find the technicians who would ready the little machines for space.

"Wow!" Dart was beside himself with glee. "We're not only pilots, we have our own ships. Which one are you taking, Bart?" He was off down the line of berths, his brother close behind; even Peter, normally the soberest, was carried away by their enthusiasm. Only Tumble stayed behind, eying Bowen a trifle reproachfully.

"You should have told him there'll only be three needed. It was white of you to keep quiet about my being a spy and an enemy, but he'll have to know soon, and it's too bad for him to waste time and trouble getting another ship ready. Maybe if I could say I was on your side—but I can't. I know now you were telling me the truth, but I can't go back on a friend until I've heard his side of the story."

Bowen nodded slowly.

"I thought that must be your trouble, when you didn't say anything after getting here.

"That's all right, as far as I'm concerned. My business, Tumble, is to get ships and men out to the planets in any way that it can be managed. We have only one idea at the moment how it can be; according to that idea, you are one of the most likely people to be able to do it. You got used to free fall quicker than the other boys, you are more skillful at maneuvering in that condition than they, you are faster in reaction than they are. The fact that I don't even know your last name doesn't matter. As far as I'm concerned, giving you rocket training will provide me with some facts I need to know; our personal problems don't count beside that. What I said earlier about your final decision still goes—you can hold off as long as you want, until you've picked up all the threads you need to make a decision. I respect you for standing up for a friend, even if I don't at the moment think much of the friend.

"I need you, and mankind needs you, in space. So, as far as I'm concerned, you're a cadet rocket pilot, on the same footing as my nephews and Peter Ashburn. Run along and pick your ship, Tumble!"

For a long moment the redhead stared at the man, with a more sober, searching expression than Bowen had ever seen on the face of man or boy. Then he smiled suddenly.

"If you need it for the record, or the license, or something, sir, my last name's Tighe." Then he was off down the line of rockets.

But Bowen noticed that Tumble Tighe stayed away from the other boys for a few minutes. Some things are harder on self-control than mere weightlessness.

TUMBLE LOSES PATIENCE

TRAINING, even in rockets, means school, and Tumble had never felt very warmly toward schools of any description. Bowen and the scientists of the station found that out quickly enough, though no one was tactless enough to ask the boy for any details about his past life which might supply a reason for this attitude. In any case, it was not an unusual one.

Bart and Dart had never been noted for heading their classes, but they applied themselves here. Peter, of course, had no trouble, but even he preferred the actual flight training, which was carried out for an hour or so each day.

"You know," remarked Tumble one day as they were checking their suits in readiness for a flight, "if it were just driving these little ships around day after day, flying in space wouldn't be worth the trouble. I thought it would be zooming around, like flying in a plane. When you're out there, though, you can't tell that you're moving at all!"

"Sure, that's because—"

"Yeah, Bookworm, you know why, of course. You know everything. I know why, too; there's nothing to be going past, so you can't tell you're going. That's not the trouble; what bothers me is that we really aren't going anywhere. We just go out, and speed up, and slow down, and do circles, and—"

"And try to get back into the station," pointed out Dart. They all laughed at this; on the first flight, Tumble had insisted after an hour's practice that he could handle the ship well enough to get it back into its berth. The instructor had let him try. For fifteen minutes he had tried to "stop" the little machine beside the station, and when he finally succeeded realized that the berth was at the edge of the spinning drum, coming past him about once every twenty seconds. He had tried to hit the power just hard enough to match its speed as it passed, and of course had gone careening straight out into space while the open door he was trying to enter had whipped on around to the other side of the station. Tumble was no quitter, and he had kept trying until he had finally learned to follow the spin of the big structure. It had taken more than an hour, however, and now whenever Tumble seemed a little too sure of himself the other boys would bring up the subject of his first landing.

"All right, kid all you want," he said this time, "but I bet you feel the same way I do."

"Maybe I did," remarked Bart, "but I don't any more. I don't want to go anywhere in that ship until I know how it's going to behave. When we started I thought I did; I thought it would be like an airplane. I didn't know that pointing the nose in a different direction didn't do a thing about the way I was going, any more than you did. Right now, I expect that all the things we're learning out here where there's no weight won't help us a bit in flying the rockets close to the moon or a planet. I'm not going anywhere in that ship of mine until Dr. Wetzel and Uncle Jim and the pilots all say I know enough to try it."

"All right, old snail. I'll be laughing at you from the highest peak in the Mountains of Light." Tumble slipped his helmet into place and sealed it to the neckpiece of his suit, cutting off any chance to answer him for the moment. That did not stop Bart from making a remark, anyway.

"Just hope it isn't your headstone that's on that peak." Tumble would probably not have paid any attention even if he had heard. The others finished sealing their suits and got into their rockets for the flight. They were dropped through the hatches, one at a time, and the lesson commenced.

To Peter, it was an interesting exercise in mathematics; to the brothers, it was about like any other piece of school work—something to be done, but not really enjoyed; to Tumble it was an almost unbearable bore. He had taken long enough, he felt, to learn that if he headed away from the station and used a certain amount of power for thirty seconds, then he had to turn around, use the same amount for a whole minute, head once more in the original direction and use yet another thirty seconds of the same power in order to get back to the station. Now they were trying to tell him that this wasn't exactly right, either; it made a difference which way he started. If he did the maneuver heading toward the earth, he wouldn't get quite all the way back; if he headed the other way, he wouldn't get all the way back either. As if this weren't confusing enough, no matter how carefully he aimed the ship, pointing back as exactly as he could along the way he had come, he never seemed to end very close to the station; it was always well to one side.

"I think these smart alecks are doing something with the controls," he muttered to himself as the ship dropped from its cradle into the emptiness of space. "It's a nuisance having someone who can make the ship do what he wants by radio no matter what I do. I bet they're trying to make me think it's harder than it really is. I'm going to do something about that." Still grumbling, he pointed the nose of the little machine at a particular star, as the instructions of the teacher in the station came through the radio, and obediently cut in the amount of power required.

He didn't finish the maneuver, however. He was used to seeing the earth, of course—above him or below him or beside him, according to whatever direction happened to be "down" at the moment. He had seen it as a big disc glowing in the sunlight, as a fuzzy-edged half moon, as a hazy crescent, and as a great circle of darkness cutting sun and stars from half the sky; but he had never seen it with a hole in it. The sight took his entire attention from the control exercise he was supposed to be doing, and he simply stared.

His instructor's voice roused him at last.

"Tumble! What's the matter? Why haven't you turned the ship over?"

"I forgot," admitted the boy. "Look, can you see the earth? There's something funny—a big, black spot that looks almost like a hole. Usually you can't make out the marks on the surface very well, but this shows up clear as anything."

"Hmph. I don't know. You make your turnover and start slowing down before you get so far away we can't talk, and I'll ask the astronomers while you're doing so."

Tumble obeyed, though his eyes still kept straying to the peculiar sight in the sky beside him. In spite of the distraction, his control work was neat and precise; the instructor had no fault to find when he came back on the radio with the information Tumble had asked for.

"It's an eclipse, the astronomers say. The black spot is the moon's shadow. The people under the place where the shadow hits are having an eclipse of the sun. The astronomers are furious because the station isn't going into the shadow, so they won't be able to do something or other they want to. They say someone should have figured all this out in advance and put the station in a path that would have carried it through the shadow cone. Scientists are funny people." The instructor was one of the pilots who had brought the station up originally.

"I see," answered Tumble. He understood what eclipses were, and needed no further explanation. "Well, I guess I kind of messed up that exercise, didn't I?"

Before he answered, the instructor examined the recording equipment which had kept track of the little ship's control movements.

"Well, forgetting the turnover when it was due could have killed you, of course, if you'd been heading for anything solid. Aside from that, you did a very good job indeed. These records are almost as smooth as though the ship had been on automatic control."

This remark may have been a mistake, for when Tumble got back to the station he went straight to Bowen with it.

"Look, Dr. Bowen. Why do we just keep flying in circles around here? We can handle those ships; Mr. Linn told me this morning that I was nearly as good as an automatic pilot."

"You can't land with an automatic pilot, and they can't make up their minds what to do. Someone has to set them. Believe me, Tumble, you're no more anxious to start exploring than I am to let you go, but I want you to come back, too." The redhead knew when arguing was futile; he left the room, still unsatisfied.

But these people did not know Tumble yet. He did not often settle down in deep thought, but when he did, action of some sort was likely to result. Bowen's refusal to recognize his skill as a pilot convinced him that the time for thought had arrived. He wandered into the now deserted section where the little rockets hung in their berths, and settled down for it.

He glanced down the row of ships. There were ten of them there, six identified only by numbers, while the other four had carefully painted names. Bart's Outbound was nearest; his brother's was the Fabberwock, which seemed silly to the redhead. Even the bookworm had carefully painted Ion on the nose of his machine, and Tumble had christened his the Tumblesauce—so that, as he said, there would be no mistake as to whose she was.

Just now the pilot of the Tumblesauce was not thinking of names, however. He knew his ship, or felt that he did; he could see no reason on Earth or off it why he couldn't take her anywhere in the solar system. Already he had been out on practice flights which had lasted longer than a flight to the moon would take. He had seen his mountains as well as anyone ever would through a telescope; but what did they look like close up? He didn't know, and never would if these cautious old fogies—even Pete—had their way. It was all very well to teach him how to use the rocket, but if they wouldn't let him do anything except drive it around in circles—how could they expect anyone to get anywhere that way?

The thought struck him again. Did they want him to get anywhere? What had Lerch said so long ago about these people? They wanted to get in first to make their own claims, he had insisted. They had denied it, of course; but they were keeping him back, just the same. How did he know that he would not wake up some morning to find the other boys millions of miles on their ways to make just that claim? He had been a fool; he had swallowed Bowen's apparent friendliness too easily. Something had to be done, and Tumble Tighe was the one to do it.

His face firmed into decision under the red thatch of hair, and the boy turned suddenly and left the dock. He had finished thinking; it was time for action.

The Tumblesauce, like her sister ships, had emergency food aboard; it was always possible that a motor would fail, and the pilot might want to eat while the rescuers were coming. Tumble had heard of emergency foods, however, and decided that it would be more comfortable to add some of the things he liked. He did this at odd times during the next week or so, when he was sure the others were too busy to notice him.

He checked the fuel tanks. Fuel was a minor problem with a Phoenix reactor, but his training had impressed on him that nothing about machinery should be left to chance. He went over in his mind the navigation problem involved—he didn't dare ask for help from either his instructor or Peter. He did work some of it out on paper, but carefully burned the paper afterward. The real trouble, of course, was not in finding the moon but in arranging to get there traveling slowly enough so that he would not blow a new hole in its already pitted surface. That was where gravity both of Earth and moon complicated matters; but Tumble was sure he had figured it correctly. Nine days' spare time went to this job.

There was just one more thing to do. He almost laughed as he realized that it was the part of ground school he disliked the most which had taught him to do it. Well, if they wanted him to learn about radios, he would show them!

He waited until the next morning before showing anyone, however. He was sensible enough to know that he would need the sleep, impatient as he was. Then, after breakfast, he joined the others at the dock. They all carefully checked their space suits, as had now become routine; each one got into his own rocket, and one by one the little machines dropped through their hatches.

Tumble did not listen while his instructor outlined the maneuver he was to try next. Instead, he had the cover off the receiver which picked up the control impulses from the station; and working very carefully, for he did not know whether the plastic of his space suit was sufficient insulation against four hundred volts, he slipped the main fuse out of its clip. Being a rather neat young fellow, he put the fuse into the repair kit and the cover back on the set; then, without saying a word to his instructor, he swung the Tumblesauce around so that her nose pointed just ahead of the moon on the latter's path among the stars, and cut in two gravities of drive.

BULL'S-EYE ALMOST

THE instructor could not, of course, see Tumble's rocket directly—had he been near a porthole, which he wasn't, the little machine would have been out of sight of the station a few seconds after launching. Even the gleam of sunlight on its bright hull could not be distinguished among the thousands of stars, if it were more than a mile or two away. For that reason, the instructor did not realize what the boy had done for more than a minute. He had been outlining the maneuver that the Tumblesauce was to perform; when he had finished, he waited for an answer, and got none.

"Tumble! Come in! Did you read me?" He paused, then repeated his calls; and when silence continued on the Tumblesauce's wave length, he cut in the circuits which tied his vision screen to the search radar of the station.

Four dots immediately glowed on various parts of the screen; but one was much fainter than the others. Shaking his head, the instructor snapped over to another circuit, and five seconds later had the distance and speed of the fleeing speck of metal. At the instant of the measurement, it had been just over thirty-five miles from the station, traveling away at almost exactly one mile per second.

His hands flew over the controls which should have spun the errant rocket end for end and started its main motor at the task of slowing down its mad flight; but thirty seconds after the first observation its distance was seventy-three miles, while more than thirty percent had been added to its speed.

"Tumble, are you out of control? Tell us please—at least send out a carrier wave; you'll be out of our radar range before long, and if anyone is going to find you with a rescue ship he'll need something to guide him."

"I'm not out of control." The words came firmly, but with no suggestion that the speaker intended to say any more.

"Then come back, for goodness' sake. You don't know what you're getting yourself into."

"I know all right. I'm tired of doing loop-the-loops according to instructions. I'll be back in a few days. There's something I've been wanting to see for a long time, and I'm going to get a good look at it."

The instructor had sounded a general alarm the moment he had finished his first check on the Tumblesauce's position and speed; at this point Bowen appeared in answer to it. A few seconds' explanation gave him the facts, and he shook his head.

"We won't be able to talk him back," he remarked. Then, into the microphone, "Tumble, you're not ready for this, whatever you may think. Please remember that making a landing where there's any gravity to speak of is a lot different from matching up with this station—"

"Who told you where I was landing?"

"You did. Time and again. I don't suppose you believe anything I'm saying, though, so I'll ask just one thing; please promise to call us if you even suspect you may be in trouble, so that we'll know about where you are and what sort of help you'll need."

"I won't get in trouble." The boy paused, then added, "I'll call you, though, anyway. I'll be seeing a lot that you'll want to hear."

Bowen shook his head at that.

"All right; thanks. Just be sure your space suit is all right before you try that landing. It probably won't make any difference, but it might." He signed off with that remark, and that was probably the best thing he could have done.

Certainly it made Tumble think for some seconds. He admitted later that he almost reached for the controls, to reverse the flight of the little rocket, but before he did so, his eyes fell on the moon above his head.

That was enough. He had seen pictures of it, he had gazed at it through telescopes; no one was going to stop him from visiting it now. He knew about allowing for gravity; he had done the problem, or ones like it, several times on paper in the last few days in preparation for this very event. He made a face at the radio, and settled himself to the task of piling up distance.

At two gravities acceleration—in other words, adding more than forty miles an hour to his speed each second —covering great distances is not a difficult job. One hour after turning on his power, he was nearly eighty thousand miles from both the station and the earth, and his speed had built up to over forty-three miles a second. Another hour would have doubled his speed and quadrupled his distance, placing the Tumblesauce well beyond the moon.

Tumble did not keep going, therefore. If there had been no outside forces acting on the ship, turning over at one hour and fourteen minutes from his starting time and decelerating at the same rate he had been using would have brought the little rocket to a halt, relative to its starting point, at two hundred and forty-two thousand miles, the moon's distance at the time. Actually, since he would have been fighting the earth's gravity, for most of the distance, the stop would come sooner; therefore he made the turnover a trifle later. He had carefully figured out just when this should be done—it was the problem he had been practicing, and he was very pleased with himself, feeling quite rightly that none of the instructors at the station would expect him to remember .the correction.

He forgot two other facts, however. One was that he had set his initial course by eye and had to correct it from time to time; therefore his slowing down was not done in a direction exactly opposite to his speeding up, and did not exactly offset it. This was minor, however; what really caused his trouble was forgetting that the station, at the time he left it, was moving in its orbit about the earth almost directly toward the moon; this fact had made him a free present of approximately four miles a second. This factor, in some eight thousand seconds of flight, added up to quite an error in distance.

Tumble did not find this out until he was about twelve thousand miles from the moon. He might not have realized it then, for he was paying a good deal more attention to the moon than to his navigation, but the ship itself called the matter to his attention.

The rocket was equipped with radar, and in connection with the radar was a tiny automatic calculator which was designed to figure the course of any large object approaching the rocket. It would sound an alarm if the object were on a course which would result in collision; the moment the moon came within the twelve-thousand-mile extreme range of the radar, the alarm sounded.

At first, Tumble paid little attention; he already knew he was heading for the moon, so the alarm was telling him nothing new. Then he remembered that the calculator automatically allowed for any power the ship itself was using, so that the alarm must mean that he was not slowing down rapidly enough. Even this did not surprise him too much; he would have admitted, if anyone had asked him, that he might be a few hundred yards or maybe a mile or two off in his calculations. He increased his power a trifle, expecting the alarm to cut out as soon as the calculator had made allowance for the change, but it kept ringing.

Tumble's next thought was that the alarm equipment must be out of order; he made two more increases of power, until the Tumblesauce was losing speed at nearly a hundred feet per second each second and the boy was sagging in his safety harness under a force of three times his own weight, but the alarm continued to ring. As a final test he started two of the tiny side motors at a power sufficient to push the rocket out of line with the moon in a few minutes. He expected no result from this move, but to his surprise the bell stopped almost at once.

It was hard to think under three gravities of acceleration, but even so he could see what that meant. Somewhere he had made a mistake. He had too much speed; unless he kept a course which would pass to one side of the moon, he would strike its surface much too hard for comfort.

Actually, his instruments were giving him his distance from the moon, his velocity at the moment, and his acceleration; it would have been easy for some people to calculate from their readings how fast he would strike—or, alternately, what acceleration he would need to make a safe landing. Peter, he reflected gloomily, could probably have done the arithmetic in his head (this was a mistake; even Peter had his limits) ; but Tumble Tighe and Peter Ashburn were two very different people. Tumble had to use trial and error; he kept increasing his main power, and after each increase edged back until his course once more intersected the surface of the moon.

Each time the bell rang again. He kept up the attempts until the Tumblesauce was slowing at nearly six gravities—until Tumble himself was being jammed into his seat by the more than six hundred pounds provided by his own inertia. A grown man would have been unconscious under the force, unless he were lying down at right angles to it; even Tumble, sagging in the control chair with his feet almost as "high" as his head, was barely able to see. He was more frightened than he could remember ever having been in his life; he knew now that his error had not been one of a few feet. It had involved thousands of miles of distance and thousands of feet per second of velocity. At last he stopped edging back toward the moon; if he struck it at his present speed there would be a new crater for someone to name. The only comfort for him was that he would never know it. He and his rocket would be a boiling cloud of gas a thousandth of a second after the blow.

The minutes passed, however, and nothing seemed to happen. With each second, the rocket was going that much more slowly, and its frightened pilot drew a tiny bit of courage from each of those seconds. For more than an hour the moon had been invisible beneath his feet; now it began to show in one of the side windows. That meant that almost certainly he would pass it safely even if he did not stop in time, and with this realization the last of his terror departed. Those few minutes of fear had soaked his clothes with perspiration, and his arms and hands were cramped with the grip he had held on the arms of the pilot chair. But that was just something to forget.

The speed dial on the radar unit dropped to zero, which did not mean that he had stopped but that he was no longer getting any closer to the moon—he was passing it. With some difficulty he moved his head enough to watch it through the port. It was only a few miles away; he had given himself just barely enough sideways velocity. It was moving very slowly, too; and as he watched, it stopped entirely and then began to drift in the opposite direction—toward the stern of the rocket. Tumble realized what that meant, and cut his power at once. He had finally gotten rid of his extra speed.

But that did not mean that he could relax. Fifteen miles above the surface of a world, even one with gravity as weak as the moon's, is no place to take a nap; the Tumblesauce might have stopped as far as her interplanetary speed was concerned, but she was falling.

Tumble swung the tail toward the surface of the moon, and applied enough power to halt the fall—the radar was useful once more. Then he began to ease gently downward. He knew about where he was; he had been aiming at the moon's north pole from the beginning, and must have stopped nearly above it. A quick glance through the ports showed the craters and mountains he had seen so often through the telescope, now standing out sharp and clear. He had trouble recognizing them, since he was seeing them from a direction no human ever had before; but he thought he could identify his favorite Mountains of Eternal Light. He was not right above them, but this was no time to change that; he had a landing to take care of.

The Tumblesauce settled gently downward. Had anyone been watching from outside, he would have seen her rocket exhaust glowing faintly, a line of light that reached downward from her tail and finally touched the surface. A wave of dust and pebbles, glowing with the heat of the stream of gas, washed outward from the point of contact and vanished as the jet swept the rock clear of loose material. Five seconds later Tumble saw his distance scale touch zero; as he cut the power to his main engine, he felt a faint jar. The rocket had fallen perhaps six inches. It stood quietly on its tail, a gleaming metal cylinder, the first man-carrying machine ever to touch the moon.

LONG WALK

TUMBLE did not know which window to approach first. From his seat he could catch glimpses of the surrounding landscape through each of them, but every time he started to look closer at one scene, another one glimpsed from the corner of his eye caught his attention. The seat was back in its normal position after holding him nearly horizontal during the period of high acceleration; there was no difficulty about leaving it. He simply couldn't make up his mind which way to go when he did.

The obvious answer finally came to him. He stood up —the gravity did not bother him; he weighed about what he did forty or fifty feet from the center of the station, and had spent plenty of time getting used to that—and started toward the air lock. If Bowen had seen him there would have been an explosion, for he had made numerous and lengthy speeches about the importance of checking the space suits before going outside a ship. Tumble forgot this until he was actually inside the air lock. When he did remember, he was tempted to go on anyway, since the lock was too cramped to let him make a proper check and he had already sealed the inner door, but he remembered the stories he had heard of what happened to living creatures when the pressure went so low that boiling point was below their body temperature, and went back. The check was done rather quickly, but would probably have satisfied Bowen; two minutes later the outer door of the air lock opened and let the boy get his first good look at the moon.

He had somehow expected it to be glaringly bright, as it had always looked in the telescopes, but the surface was almost entirely of dark-colored rock. From where he stood he could see nothing looking in the least like soil, but when he worked his way cautiously down the ladder he found that the cracks in the rock were filled with powdery dust. Close to the rocket there was none of this loose on the surface, but farther away a layer of it could be found up to two or three inches thick. Apparently it had been blown away from the landing site by the jet.

In general the surface was fairly smooth in spite of the cracks, but low mountains could be seen in several different directions. He was not sure which, if any, of these were the Mountains of Light he had come to see, but there would be no difficulty in identifying them from above when the time came. Tumble's fear had completely gone by now, and the thought of taking the rocket up again did not bother him in the least.

He had not expected that landscape features would be so hard to recognize from where he was standing. He had studied the north polar region for hours in the telescope at the station, and would have sworn that he knew every major peak and crater in the neighborhood, but they looked very different now. Perhaps the fact that the sun was just barely above the horizon would account for it—but no, the sun never rose very high this close to the pole; even Tumble knew that, though he was no mathematician.

Looking toward the sun brought another thought to his mind, and he began looking around for the earth. It was visible enough, nearly a quarter of the way around the horizon to the right of the sun, and like it just barely above the mountains. It was far brighter than the moon ever appears from the earth, but the fact was not very noticeable with the sun also in the sky. It was rather less than half full, but Tumble could not have said at the moment whether it was coming or going in that respect. It did not occur to him to wonder—it did not seem important at the moment.

It did, somewhat later.

However, whatever this place might be, it was a long walk from the Mountains of Light. He might as well get back up a few miles and find them; they were what he was interested in, and anyway he could probably see more from a mountain top when he did get there. He walked back to the ship—at least, the moon's gravity made walking in the space suit a lot easier than it had been on Earth—and climbed the rungs up to the air lock. The door controls worked normally and he entered without trouble, but that was more than could be said for the drive.

Tumble had closed his master switches and turned up half a gravity of acceleration without strapping himself into his seat, and at first he thought that there must be some safety control that no one had told him about which kept the motor from working if the pilot were not safetied at his post. However, fastening his straps made no difference. The motor refused to work.

He unstrapped, rechecked his suit; and went outside to look things over, but he could see nothing wrong with the drive unit from there. Back inside, he looked helplessly at the panel of switches, knobs, and indicators, and wondered what to do. He was not an engineer, and even if he had been able to get the covers off the panels, the sight of the wiring inside would not have helped him. He did not know whether it was a general power failure, or—

But wait a minute. His lights, at least the ones on the instrument panel, still worked. So did the cabin ones, as he found by experiment. The failure could not be general, then; perhaps his side jets—the tiny thrust units used normally for turning the rocket so that its main engine pointed in the right direction—might be working. He tried one, without stopping to think.

It worked, and that was a trifle unfortunate, for Tumble had not considered what would happen if it did. He should have tested two at a time, with the two pointing in opposite directions. As it was, the thrust of the single unit was quite enough to start the tall cylinder of the Tumblesauce—which was not too well balanced anyway, since Tumble had forgotten to extend its props before landing—tipping gently over.

The boy was a shade slow in realizing what was happening, since his eyes were on his control panel and he had just spent a good many days learning not to believe his sense of balance. He was halfway over when he started the opposite steering jet; since the ground was not quite level and the Tumblesauce had already rolled a short distance barrel-fashion, that unit was not pointing in the right direction to straighten the ship up again. It slewed violently sideways, landed in a horizontal position with a clang of metal on rock, and rolled over twice before stopping. Tumble had not been strapped in, and it was luck and his space suit which saved him from a good collection of broken bones.

Since the Tumblesauce was lying with her air lock underneath, the boy had to do a bit of maneuvering before anything at all could be accomplished. By standing on the inner door of the lock, he could reach the control panel easily enough and give a brief jolt of power to another side jet; then he had to move fast to save himself from another fall, since there was no way to strap himself in that position. Eventually he had the rocket lying with its air lock on the side, however, and was free to consider his next move.

He could never handle the side jets well enough to stand the ship up again; he knew that. He would not dare use the main drive even if it worked, since it would simply send the ship skidding along the surface of the moon to tear open against the first projection of rock it might hit. Much as he disliked the thought, it looked as though he would have to call for help.

Unfortunately for this idea, the radio did not work either. Since the small rockets were meant for work principally in space, no particular attempt had been made to streamline them; and the transmitting antennae projected from their sides. The rolling of the Tumblesauce had of course broken these off. The receiver was working, but no signals were coming through. Tumble listened for a long time to make sure of that.

There was an excellent reason for the lack of messages. The station was at the moment over the south pole of the earth, and below the horizon from Tumble's part of the moon. Its course took it from there to the far side of the earth, and by the time it reappeared at the north no message would have done any good.

Tumble could think of only one more idea. He realized that Bowen and the others knew of his interest in the Mountains of Light. Undoubtedly the other small rockets would come in search of him, and that was the logical place for them to search. He had better be there when they arrived.

He removed his helmet and ate as much as he could hold of the food he had stowed on board the rocket. There would be no way to eat it later; that was one provision which had not been made in the space suits. He took a good drink of water, though the suit did recondense what he breathed out; then he took a last look at the control room, climbed awkwardly out the air lock, and prepared for his long walk.

It now was necessary to decide which of the several elevations which he thought must be mountain groups at the horizon was the one he wanted. He had lost his direction completely during the landing, and was not astronomer enough to regain it from the direction of the sun and the earth. The stars might work, but he could not see them, and the sun might be days in setting, if it ever did.

Then he remembered that with no air, it should be possible to see the stars anyway if he got the glare of the sun and the surrounding rocks out of his eyes. He backed against the hull of the rocket, folded his arms between his face and the sunlit hills in front of him, and looked directly up.

The stars were clear enough; there were just too many of them. Whatever minute traces of atmosphere the moon might have meant nothing as far as cutting off starlight went. It took a long time to recognize any of the few constellations he knew among all the extra points of light, but at last he picked out the Big Dipper, and from that was able to find the North Star.

That satisfied him. The Mountains of Eternal Light lie close to the north pole of the moon—so close that the sun never sets- there, as Tumble well knew. That meant that if he reached the north pole, the mountains would have to be above the horizon, and should be easy to recognize. He was sure he could not be very far from the pole.

The North Star was very high above the horizon, so it was a little difficult to use it to decide which way was north; but after several checks, the boy felt he had picked the spot on the horizon that was most nearly under it.

For just a moment longer he hesitated. He looked sorrowfully at the Tumblesauce, for he had grown fond of the little rocket; then he faced resolutely in the direction he had chosen, and started to walk.

OPERATION SICK BAY

BOWEN did not wait for Tumble to report himself in trouble before getting into action. As far as the man was concerned, the young idiot was already in trouble, and the possibility that he might get out of it by himself was not worth considering for a moment.

Although there was no question that something had to be done, there was less agreement about what it should be. The Ranger brothers were all for starting after the Tumblesauce in their own rockets. Bowen had a hard time convincing them that they were not much more likely to keep out of trouble than Tumble himself —they simply weren't adequately trained. If anything, Tumble was the best pilot of the lot, according to the instructors.

"But, Uncle Jim, you're not worried about Tumble's piloting abilities; you said it was his general knowledge of what to expect, and his navigation. Pete, at least, is way ahead of Tumble in both those points, even if Dart and I aren't."

"I know, but none of you is good enough to risk that far from the station. Besides, what could you do? That young idiot will certainly try to land on the moon, and he'll do it before you could possibly get there. Probably there won't be enough left of him or his rocket to see from above, and there are too many holes in the moon's surface already to be able to tell where he hit that way."

"But we have to look. We can't just forget him."

"Of course. But before you look, we can do two things: we can get you some practice in simulated gravity landings, so that at least your necks won't be broken if you have to go down to pick up his pieces, and we can start a search for the kid with the telescope."

Peter jerked upright in his seat, and several of the other listeners looked a trifle surprised.

"But—you couldn't possibly see either him or his rocket in any telescope in the world at this distance, to say nothing of the little thing we have in the station here."

Bowen nodded slowly—and grimly.

"You're quite right. We can't possibly spot him from here. We can't coordinate a search by you boys very effectively from here. Nevertheless, we're going to search." He looked around at the group of men seated in the big assembly room. "Does anyone feel that we don't have to do our absolute best to find that kid? Does anyone feel that it's not our fault he's out there? Sure, I know we didn't ask him to steal that rocket, but we taught him to use it; we gave him the idea that he was better than any of us, and that none of us had any right giving him instructions. My boys here know the difference between brains, or common sense, or whatever you want to call it, and the ability to float around in free fall without having your stomach tied in knots, but that kid is younger than they are, and I don't think he's had as much chance to learn to use his head as they did. He knows he can stand space better than we can; to him, that means the same as saying that he's a better spaceman than we are. We might have gotten the difference across to him if he'd been around long enough—and if he lives through this, which I don't expect him to, maybe it will teach him something. But can anyone here say it isn't up to us to find him if he's findable?"

There was silence for several seconds; then one of the men in the back cleared his throat. Bowen looked as though he would have used a gun had there been one around. "Yes, Mr. Polcek?"

"I just wanted to remark, Dr. Bowen, that you're quite right, but that there's another reason than plain duty for searching. I rather like the little pest." There was a general hum of agreement, and Bowen's expression relaxed.

"You'd better command during the shift, Dr. Bowen," Wetzel added. "You can coordinate our emergency pilots better."

"Good enough. In that case, the only question is the program. It will obviously be necessary to train at least one, and preferably all three, of these boys to make at least the preliminary maneuvers of this station—"

"What?" asked Bart, who had not seen quite all that was behind the last few words of the men.

"Quite simple, Bart. The station will have to get out of this orbit, into another which will take it to the moon, and from that into another around the moon so arranged that we can search as thoroughly as possible with the telescope. To change orbits, we will have to stop the spin; it is very doubtful that any of us will be able to hold out without weight long enough to get a new orbit set up. We will try, of course, but I imagine that before it's done we will all have had to use the pills, and you boys will have to finish up the course corrections and get the station spinning again."

"I—I see. But—can't you take the pills first and let us do the whole job? Then you'd be all right when you woke up; the way you suggest, some of you may be in bad shape for weeks."

"True enough. The reason is time. We could train you to do the whole job, but to be absolutely sure would take days. This way we can take the chance of a shorter training, and the longer we last to do the job ourselves the less you'll have to worry about forgetting something. We'll write out directions, or course, but it isn't always possible to read such things fast enough—you've found that out already, I expect."

"That's true. All right, what are we waiting for?"

"Nothing. Come on." Bowen rose and started toward the main control room of the station, followed by the boys, the four pilots now on board, and the ballisticians, who had also been acting as instructors to the boys during their training.

"The maneuver shouldn't take too long," Uncle Jim went on. "Stopping the spin without damaging any equipment will take about two minutes, and to swing the station so that its main drive is pointed right will take between two and three minutes with the tiny steering motors we have. That's about five minutes, and that's the critical time; if we can last through it, we're all right. After we're lined up we can put on one gravity of acceleration and be comfortable.

"Stopping the spin won't take any skill, but lining up right will; we'll have to do a bit of calculating to find just what the right line is, and then just what steering motors to use to put the station on it. That last will depend on just where Motor Number One is when we stop spinning, and the directions may have to be a bit general for that reason. That, primarily, is why it would take so long to train you boys to do the job, and why it would be best if one of the regular pilots could last long enough for it."

For a few moments, the boys had had glowing pictures of commanding the huge station while all the grown men slept through its maneuvers; but Uncle Jim's outline of the problem took a good deal of the attractiveness from the picture. The brothers were just barely able to see what the problem was, and it came close to scaring them. Peter saw very clearly, and came that much closer to being scared. No one hoped more fervently than he that the pilot would be able to keep control of himself through the time of changing weight.

The next few hours were busy. Again and again Bowen and the pilots went over the controls with the boys; again and again the observers and astronomers checked their calculations as to the time when spin would have to come off the station, what its new heading should be, and how to get pointed that way. Actually, the entire problem could have been set up on automatic controls, as the flight of the Polaris had been —if only the station had been equipped with them. It had never been intended to leave its original orbit, however, and it was fortunate for everyone concerned that the plan of dismantling its main motors and taking them back to Niagara had not yet been carried out.

The hours passed while the station swung across the Antarctic Continent, northward over the darkened Pacific, and into the eight-thousand-mile-wide column of space where the earth hid the moon from view. Some of the observers had been attempting to catch a glimpse of the Tumblesauce, foolish as they knew such a hope to be; now they stopped, along with the radio operators who had been listening for messages from the missing rocket. They did not relax, however, for there was still plenty to be done. The people who were not needed, or who could not help in the coming maneuver, went to their quarters, made sure everything loose there was fastened down, and improvised sheets or blankets into harnesses which would keep them in their bunks while weight was gone—and when it came back in a new direction. Some of them may have planned to stay awake at first to see whether they could take it this time, but none of them really expected to be able to.

Similar precautions were taken all through the inhabited part of the station. In the control room, the seats were already designed so that a man sitting in one could reach his controls, whichever direction happened to be down, but a good deal of movable material had gathered there during the weeks the station had been spinning. Once spin ceased and the station began accelerating toward the moon, all that stuff would fall to the new floor —and might hit a man or a control switch on the way. Everything had to be checked; time and again the boys thought the job had been done when someone pointed out another item to be removed or fastened. Peter decided that when he got back to Earth he could make money betting his friends that they couldn't go into an ordinary kitchen and list in one hour all the articles which would move if the house were suddenly turned on its side. He felt like an expert himself, by now.

The moon appeared again, seen across the wastes of the Arctic, but no sign or signal of Tumble registered on telescope or radio. Room after room was now being reported ready for maneuvers, and gradually the earth's gravity swung the big metal drum of the station into a line as close as it would get to that needed for the long flight.

The answers had come from the calculators, had been checked, and had agreed with each other. The crew, except for the boys, Bowen, and the pilots, were fastened in their bunks ready to take their sedatives when the signal came.

In the control room, Bowen and the two pilots were strapped in their chairs, with one of the boys standing behind each of them. The boys themselves had firm grips on some of the numerous hand straps attached at various places on walls and furniture, and like the men were watching the outside view screen which had been set on Earth. The edge of the planet was fixed on the crossed lines of the screen, and a star was approaching it slowly. The edge was hard to locate definitely because of the blurring caused by the atmosphere, but a photocell had been rigged to sound an alarm when the atmosphere cut down the star's light by fifty percent. From then on, all actions would follow a strict schedule. Actually, the program was being controlled by time, and had already been set up; the photocell observation was simply a final check that the station was still in its regular orbit.

Tension mounted as the star approached the line; the hands of the boys tightened against the chair backs and those of the pilots strayed constantly nearer their switches. A clock set in the wall was also the object of frequent glances; its second hand should reach the quarter-minute at the same moment the alarm sounded. Actually, the alarm was five seconds late, but the pilots had seen that its error could not be great and had not waited for it. Skilled hands flashed from switch to switch, the boy's eyes following their motions closely, and everyone in the room felt the queer, sideward lurch as the station's spin began to slow. For several seconds "down" seemed merely to shift a few degrees to one side, so that walls and floor appeared to be on a noticeable slant; then weight began to decrease enough to be felt. The boys tightened their handholds, but no longer let the falling sensation bother them; the pilots seemed too busy to notice it, at least for the moment. Bowen, however, tensed visibly in his seat. Bart, behind him, could guess what was going on in his mind as weight grew steadily less and the seeming fall grew faster and faster. The man's hands tightened on the arms of his seat, and by sheer effort of will he kept his attention on the clock and the maneuver checklist.

"One minute." The boys hardly recognized the voice, but if the strain in it bothered the pilots they gave no sign. The seconds crawled by, with Bowen frantically checking his list, the instruments, the actions of the pilots, and anything else that might serve to keep his mind from the frightful sensations he was enduring. The boys had said it was easy—all right, so he was falling; what difference did it make? So was the moon; so was the earth, and they never hit anything. His mind knew he was safe, but his body didn't believe it. For forty-five years his nerves had been set to sound a general alarm to his body when those sensations came in, even if they were caused merely by stepping off an unexpected curbstone. Never before—except in his three previous experiences of free fall—had the sensations lasted so long; something must be seriously wrong, his emotions said.

"Two minutes. Twenty seconds stops us." The clock brought his mind back to business for a moment. "Screen Two is positioned. Stop all spin with Rigel on its center line. The star is in the field now—you have about twelve seconds to correct. Too much; ease off the torque a trifle—that's it—Dart, on your toes!" The last words were almost screamed as the pilot in front of the younger brother suddenly jerked his hands from the switches, moaned, and gropingly brought to his mouth the pill which had been held to his control panel by a tiny piece of adhesive tape. Dart responded instantly; his mind and eyes had been following the pilot's actions throughout the maneuver, and while he held on with his left hand his right flew over the unconscious man's shoulder to the vernier dial which needed adjusting.

The other pilot glanced up for an instant, and Peter thought that he would also have to take over; he remembered how the sight of one person's becoming airsick usually was enough to set several others going. It did not work that way this time, however; the pilot claimed afterward that the incident had distracted him from his own troubles just in time to save him.

The whole thing was over in less than five seconds.

Screen Two showed the blazing, blue-white dot of Rigel almost exactly on the micrometer line, and motionless; Bowen was in no mood to make the fractional degree correction needed to center it exactly.

"Main drive—one G!" he ordered, and the pilot cut in another master switch and spun his main vernier dial up to the indicated amount. As he did so, weight came back, and with a groan of relief Bowen settled into his chair, to which only the safety straps had held him.

Bart looked at him with a triumphant grin.

"You made it, Uncle Jim! You didn't have to—"

"I'm afraid you're not quite right, Bart." Bowen interrupted in a tired voice. "I made it, in one sense, but maybe I shouldn't have tried. I'm afraid it's the wheel chair again for me; this room won't stand still."

Thirty minutes later, the score was in. Bowen and both pilots were out of action, with their sense of balance gone—even the man who had taken his pill just before the end had apparently done it too late. In addition, six other members of the station crew were unable to walk, in spite of having slept through the period of changing weight. These hard-hit men were the ones, it turned out, who had done the most experimenting with ways to get used to the sensation, in the first days after the launching of the station. Apparently their nervous systems had gotten used to the feeling, but in the wrong way; they now responded even when the men concerned were unconscious. This was not quite certain, since no one can tell just how deeply or for how long a given amount of drug will affect a man, but the station doctor worried as he thought of the other end of the trip.

At any rate, there would be three and a half hours of normal weight before that problem had to be faced. Bowen, characteristically, did not wait that long to face it; it occurred to him that if no one cared just how the station's "poles" were pointed when they put spin on it at the other end of the flight, it should be possible to shift gradually from one kind of acceleration to the other, so that the only inconvenience would be the gradual change of the "down" direction from the flat face of the great drum to its outer edge. There would not have to be a turnover, as had been needed with the Polaris; there were full-sized motors in both faces of the station, and they simply would shift from one set to the other when acceleration had to be reversed. He was quite happy with this idea, and set to work calculating just when and how power would have to be applied to perform this trick.

In the meantime, the boys were sent out to practice "landings" on the "upper" side of the station, as the best substitute for an actual gravity field. They couldn't actually land on the drum, since their rocket exhaust would have burned through its hull in a few moments; but they tried stopping at the same "level" a hundred yards or so to one side, which called for all the same maneuvers except the final cutting of power.

Unfortunately, Bowen's plan didn't work perfectly. No one had cared much about the precise shape of the orbit which the station would take up around the moon; that was why—or partly why—Bowen had not bothered to put Rigel exactly in its planned position on the screen. No one expected to make any corrections; the station would simply pass the moon, and as it reached its closest point, cut off main power. If things were planned right, it would have a speed about right to make it circle the moon as it had the earth.

Unfortunately, observation showed that if this plan were followed out, the station would actually strike the moon—that Bowen should have taken the time to make that last correction. As a result, another short spell of weightlessness had to be suffered toward the middle of the flight while a hasty correction was being made; when the station was finally set in its path about the moon, spinning as it should and ready to serve as a base for search operations, the men on board it were practically hospital cases.

Some staggered as they walked; some could not walk. Some could not sleep without nightmares. Several could not eat—or, if they did, could not control their stomachs sufficiently to keep the food down. It was the first time the boys had really appreciated their own luck, and Peter admitted that if he had realized clearly at the beginning what the disturbing of his weight could do to a strong and intelligent man, he would never have dared participate in his own idea, or even suggest it.

Bowen heard this remark, and nodded ruefully from his improvised wheel chair.

"I never had much faith in it, but it was something worth trying. Now it turns out to be right. The only catch is that a certain number of boys your age are going to be scatterbrains like Tumble, and if we don't find him, which we probably won't, who's going to let us start a training program for teen-agers? It's up to you fellows—not so much to find him as to do such a good job of looking that you'll offset any ideas which his own nonsense may start in people's minds."

The boys saw this, and nodded soberly; the four settled down to plan the search.

THREE RANGERS

THE station was provided with photographic mapping equipment, which had been intended for use in meteorology observations of the earth. This was put in service the moment the moon was within range; by the time the new orbit was established, enough finished maps were on hand to permit planning the search, or at least the beginning of it.

The approach to the moon had been over its north pole, as Tumble's had been. This was not luck, of course; Bowen and everyone else aboard had known where the boy would try to land. While no one expected that he might have succeeded, the Mountains of Light offered at least as good a center as any other from which to start searching. They planned accordingly.

Naturally, half the moon was in darkness and the region of night reached very close to the pole. Of the daylit portion, well over half had been known and mapped for many years by telescopes on Earth; the rest had never been seen by human eyes until now. The last fact would have been exciting at any other moment, even though the photographs showed that the hidden side was no different from the one already known.

Both parts were rough. Even the floors of the great walled plains such as Shackleton and Scoresby, which appeared smooth from a distance, were seamed with cracks and irregularities quite deep enough to hide the Tumblesauce or her wreckage. To make the search by eye would mean spiraling outward from the north pole at a height of not more than two thousand feet, traveling at not more than fifty miles an hour or so. It would be impossible to coast along such a path; the search ships would have to "hang" on their rockets, at a cost in fuel which would have drained the tanks of any old-style chemical-powered rocket in a few minutes. The Phoenix reactors could last much longer of course, but the time needed to cover the surface of the moon by such a method with three searchers came out to about fifteen months by Bowen's arithmetic. Searching by eye did not seem such a good idea.

An alternative would be to modify the regular radar equipment in the small rockets so that it could be used for "sweeping" the moon's surface. Similar sweeps could, of course, be made from the station itself, but it would take nearly two weeks even that way to cover the surface without changing the orbit. Working from the small rockets was very decidedly better.

The alterations were commenced the moment this was realized, and more than six hours were spent at the job. The boys were ordered to sleep the greater part of this time, and even Dart realized that this was the wise thing to do. They went to their rooms and were awakened only when the technicians reported that the radar would be ready in about another hour.

Still chewing the last of a hasty meal, they appeared at the main control room, which Bowen had been using as an office, and found the man in an extremely serious mood.

"Sit down, boys."

"But hadn't we better get going?"

"Soon, but I have something to say first.

"I realize that all three of you have a good deal of common sense; if I didn't know it, I wouldn't have agreed to any of this business. I know that there are a lot of things that can tempt you, though, as they did Tumble; I want you to realize that if you yield to any impulse to depart from the planned search line, for any reason whatever, it may mean that men will never get into space as they should. You are the pioneers—the vanguard. If Columbus hadn't come back from his voyage, it would have been a long, long time before anyone else would have ventured west on the Atlantic. The same is true here. I'm not saying much about what will happen to the people who let you go, if you don't come back; in that case, I wouldn't much care about myself. What I am worried about is your own safety, and the future of space exploration. You're the scouts—the eyes —the leaders."

"You might almost call us the Rangers," Dart said with a grin. His uncle smiled also.

"In a way, I suppose you might—although that would seem to leave Pete out, wouldn't it?"

"I don't know about that," Peter himself said. "I'm practically one of the family, anyway. If you're going to make puns on the name, I guess I have a right to get in on it too."

"Then Rangers we are," said Bart.

"Good enough." Bowen was willing to devote a little time to side issues, but not much. "Whatever you call yourselves, though, we all need you—alive. Don't get the idea that you can prove yourselves brave by ignoring safety rules. You're doing something I can't, and probably never can; I admit that, and if you want to consider yourselves better than I am, I can't blame you. However, I'd be extremely cautious if I were in your shoes."

"How does our being able to overcome space sickness prove we're better men?" asked Peter in genuine surprise. "Any ten-year-old can crawl through the Needle's Eye on Mount Monadnock, and I can't, but that doesn't make him better than I. You're still the head, Uncle Jim; as you say, we're a set of eyes. We'll try to be good ones. In the old days, it wasn't the rangers or the scouts who were leaders of the parties going west; the leaders stayed with the main group, while the scouts came back and reported. That's us."

"Three Musketeers," remarked Dart. The older boys made simultaneous grimaces of disagreement.

"Three Rangers, if you like," amended his brother, "but who ever heard of the Musketeers exploring? Besides—" He stopped suddenly.

"Besides, there were really four of them," Peter finished for him, softly.

"Yeah. Let's go." Bart's voice was husky, and Dart's expression unusually sober. Bowen knew better than to say anything as they made their way to the launching racks.

Five minutes later the boys were in their space suits, and the air locks had closed behind them. Bowen and the technicians left the launching chambers and sealed their inner doors, and one by one the three little rockets dropped away from the station.

There was no question of velocity or acceleration errors this time; every second of the search flights had been computed by the machines in the station. Seen from the great drum, the rockets appeared to drop behind as the boys applied power; actually they cut downward, killing the station's speed around the moon as they went in a single smooth curve that brought the three of them to a point twenty miles above the north pole of the bleak world just as the last of their velocity was lost.

The station's orbit was far enough out so that it would still be some time going below the horizon and out of radio range.

The three rockets swung tail downward and applied enough drive to hold them where they were against the moon's weak gravity.

"All set, Pete?" Ashburn heard Bart's voice over his radio.

"All set. We're holding our height, unless this radar altimeter is crazy. As soon as the search antennae are out, we can start 'spiraling. I'm extending mine now." Peter suited action to the word, touching the switch that would open a tiny hatch in the skin of the rocket and send out a mechanical arm carrying the modified antenna at its end. Bart checked on his brother's progress while this was going on; Dart was having no trouble.

"All right, Uncle Jim. We're in position, and the radars are registering—though the moon certainly doesn't look much like the moon on the radar screen, I must say. How will we recognize the ship if it is around?"

"It's metal," replied Bowen. "Even if it's in small pieces, as it probably is, it will reflect radar waves better than any of the rock. It should show up as a bright spot on your screen. The technicians set the contrast to help you as much as possible. You can start your search pattern whenever you're ready."

"We're ready."

The rockets began to move outward, each in its own direction. They were still hanging tail downward, tilting ever so slightly in the direction of travel—the thrust of the motors was being used mostly for support.

When the required speed was reached, the little ships straightened up again and coasted onward, tilting a trifle from time to time in one direction or another to correct course, but generally keeping their noses straight away from the moon. Peter was reminded of a group of sea horses he had once seen in an aquarium.

The motion straight away from the pole lasted a short time; then each ship began to swing to one side so as to travel along a spiral course—a course which would let their radar beams cover every square foot of the moon's surface as they wound slowly toward the equator.

They held a height of twenty miles, and the circle covered by the beams on the ground was about the same diameter. It took, therefore, several turns of the spiral before the Tumblesauce, some eighty-five miles from the pole, was reached; but it had not taken very long to make those turns, and neither the boys nor Bowen were able to believe that the search could be over so quickly.

"There must be free metal on the surface of the moon," the man said when Dart reported the glow on his screen. "After all, there's no oxygen to rust it."

"That may be true," replied Peter, from his own position, "but we can't take it for granted. Shall the rest of us continue the pattern while Dart goes down to see, or should we go over to keep an eye on him?"

"Why not try to get Tumble on the radio?" asked Dart.

"He'd have heard us long ago if he'd been able to receive," pointed out his brother.

"I think you boys had better go over and stand by while Dart goes down," said Bowen, ignoring the interruption. "Dart, hold where you are until they get to you; then ease down until you can see the surface clearly enough to tell what's showing on your screen."

"We're a hundred miles from him and each other," pointed out Peter. "He'll have to keep his transmitter putting out a carrier wave until we get there, so we can use the radio compasses. Otherwise we'd be a sweet time finding him."

"Right enough. Dart, do that. Tell me when you're together again. While you're waiting for them, Dart, give us the location of that spot on your map as well as you can—I know it's hard to identify map features on the radar screen, but you can tell about where you are by sight, I should think."

"All right, Uncle Jim."

It took some time for the boys to get together, even with the radio compasses, since it was extremely hard to recognize the rockets by sight even at a half mile's distance, against the star-sprinkled darkness. They finally managed it, however; and under Bowen's direction, all three eased off their motors a trifle for a moment and began to settle toward the surface. All the boys wanted to look downward as they went, but could not; they had to keep their places at their control boards and watch the instruments with care. All three of the radar screens now showed the spot Dart had found, and there was no trouble keeping over it, but no one got a direct look until Bowen told them to hold their height at half a mile from the ground. Dart, faster or more careless than the others, was the first to switch his attention from the controls after stopping his descent, and it was he who first spotted the source of the radar reflection.

"It's him!" he almost shrieked, forgetting any grammar he might have known.

"You can see Tumble himself?" Bowen's voice came back. "I don't believe it."

"Not Tumble, but his ship." Bart took over the reporting. "There's no mistake about that, but it's down on its side."

"He couldn't have landed it that way; he'd have had enough sideways speed to spread the rocket over a mountain," pointed out Bowen.

"Well, I can't see any break in the hull from here. I can't see Tumble either, but he might be inside—or maybe I just couldn't see him at this range; the ship itself looks pretty small. Which of us ought to land, Uncle Jim?" There was a pause before the radio gave answer.

"The station will be below the horizon from where you are in about eighty minutes. If you can get down, look around, and back up again in seventy, all right; but otherwise you'll have to wait until the station comes around again, and come back here in the meantime."

"If we don't go down now, we may not be able to when you come back," Peter cut in. "The sun is pretty low here right now, and I don't think you'd want us to try our first planet landings in the dark."

"Good point. All right, you and Dart go down; Bart, hold where you are and watch them. We haven't been able to spot your ships with the big telescope yet, and probably won't—they should have put running lights on them—so we can't watch you from the station. Put out your gear, and ease down slowly, Pete and Dart."

"What gear?" asked Dart. "The radar's already out, and it won't help."

"That's right, you wouldn't know, since you haven't actually landed anywhere but in the cradles here. There are retractable legs designed to keep the engine block off the ground when you make a tail landing; it's not such a good idea to get the tubes blocked, you know."

"I suppose it would blow us up pretty thoroughly," remarked Peter.

"It would, except for the fact that you have safety switches which will keep the motor from starting if the block has weight on it, or the tubes don't let gas out; so if you land without the legs out you'll stay right there." He explained the location of the switch controlling the landing gear, and the boys carefully checked that it had extended, looking at each other's ships to be sure; then, safe on that point, they eased off their drives once more and settled the last half mile to the surface of the moon.

Dart was in the air lock almost before his instrument needles had dropped to zero; Peter was a little slower, but wasted no time. Their ships were about two hundred yards apart, and perhaps twice as far from the helpless hulk of the Tumblesauce; Dart's Jabberwock was a trifle closer to it than Peter's Ion. By rights the younger boy might have been expected to make a dash for the crippled rocket; but something held him back until Peter caught up, and together they walked toward the little metal cylinder and whatever secret it might contain.

PETER THINKS

"THE outer door is open." Peter's voice came through his suit radio to the receivers in Bart's rocket and in the station. "He's been outside, I guess; he must have lived through the landing."

"I bet he has some bruises, if the ship is on its side." Bowen spoke roughly, trying to mask the relief he felt, but Bart could tell his real feelings. Peter and Dart could not hear him, as the amplifiers in their suit radios were not powerful enough to make the station audible from its present distance. They were not listening anyway; they were standing outside the open air lock engaged in a wordless argument over who should be first to go in. Peter won, and by the time Dart had followed him, was able to report that Tumble was nowhere to be found. They tried to call the station on the Tumblesauce's set, but of course had no luck, and had to go back outside to inform those above that the ship was empty. Its metal walls naturally cut off any suit-radio contact between inside and out.

Bowen's relief at the evidence that Tumble had survived his landing vanished at the new report, and he expressed himself rather forcefully.

"For the love of Mike! I thought every six-year-old on Earth had read enough flying stories to know that the sensible thing to do when you're forced down is to stay with your ship! Even if that young idiot can't read, you'd think he would realize that we could find the ship more easily than a space suit—blast it, we never would find a space suit; they're plastic, and won't look any different on a radar screen than the rocks of the moon! Where on the moon does that silly redhead think he's going, anyway? Did he discover a hamburger stand during his approach, and think he'd better walk over to it in case we didn't find him by breakfast time? Bart, tell those eyes of ours down there to see if they can find any sort of tracks. I suppose we'll have to keep looking, though I'm tempted to wait for him to come back from his little walk." Bart relayed the important part of this message to the boys down below, and they obediently spread out to look for traces of the elusive Tumble.

They were not long finding them. The dust which covers so much of the level areas of the moon had been swept away in a fairly large circle about the landing point of each of the three ships, but outside those circles it was quite thick enough to take footprints. Tumble's trail was still perfectly clear some thirteen hours after he had left it—with no wind or weather on the moon, it would probably be equally clear after as many thousand years, Peter guessed. Dart was the first to come across the trail, which led from the helpless Tumblesauce toward a low hill a mile or so away. He reported his discovery, and waited for orders while Peter came over from the area he had been searching. Instead of instructions, a question was relayed by Bart.

"What direction did he take?" Bowen wanted to know. The boys looked a trifle blank when this message was relayed, and Dart looked around unthinkingly for something which might tell him which way was north.

"Wait a minute," Peter said. "I'll have to go back to the Ion and get one of the maps. You had the north pole marked on those, I believe, even though there wasn't time to get the regular longitudes transferred from the telescope maps. We know pretty well where we are, and should be able to recognize some of the mountains around us on the map; then we can figure direction." He suited action to this speech, heading back toward his rocket as fast as his armor would let him—even in the feeble gravity of the moon, the space suits were rather awkward things to carry around. He had no trouble finding the maps, which had been clipped to the side of the control panel for use in the search, and he quickly selected the ones which covered the area where he was fairly sure they had landed. He picked these up rather clumsily in the gauntlets of his suit and went back out through the air lock.

By the time he had returned to the point where Dart was waiting, however, a little trouble had developed. The maps were photographic copies of the ones made at the station. They had been properly exposed, developed, and fixed, and dried sufficiently for any ordinary use—a photographic technician on Earth would have said they were completely dry. However, objects don't really get completely dry anywhere on Earth or under Earthlike conditions; when Peter exposed the prints to the nearly perfect vacuum of the moon, there were quite a few molecules of water left in the gelatin and paper. These proceeded to evaporate as he walked, and as they did so the prints began to curl, He was not watching them, and when he raised them toward his helmet after reaching Tumble's trail he was rather surprised. Without thinking, he tried to flatten them with his heavy gloves; and immediately the dry, brittle shards of gelatin flaked away from the paper, dropping gently to the ground and leaving him with a handful of maps almost as good as the Lewis Carroll ones which "had been left blank so that they would be easier to read."

Dart looked at the sheets with sheer amazement, and left to Peter the problem of reporting what had happened. Bowen himself was a little surprised, but after some moments' thought was able to make a good guess at the cause of the phenomenon.

"They'll have to do your spotting from inside the ships, I guess," he said to Bart at last. "Dart's maps are still all right; the two of them can use those inside the Jabberwock. We'll make up another set for Peter, and he can pick them up when he comes back to the station, if he still needs them."

The boys had already started toward Dart's ship when Bart relayed this information; Peter acknowledged the message. The air lock, like that in the Tumblesauce, would hold only one at a time, so there was a little delay in their getting together over the maps. At last, however, they found one on which the pattern of mountain ranges and walled plains, revealed by the long shadows near the pole, seemed to match the region where the rockets stood. This also checked with the spot where Dart should have been according to the original search pattern. They asked Bart if he could make a further check, but he felt that it might take his attention from his controls for too long a period. They decided to be satisfied with what they had.

According to their estimate, they were located five degrees—eighty-five miles, on the moon—from the north pole, well beyond the region seen at "average" times from the earth, but still at a point which could be and had been mapped from Earth at favorable times. North of them, just beyond the horizon, was a range of fairly high mountains running in a direction which would have led a person trying to reach the pole well off to the right of his course. Near its farther end this range passed fairly close to the rim of the crater within which the pole was located; and it was this part of the range whose peaks received sunlight at all times, owing to the fact that the moon's axis is not tilted like Earth's.

The "land of the midnight sun" is an area extending only about twenty miles from each pole of the moon, while on the earth its radius is about sixteen hundred miles. It is quite easy, therefore, for a mountain in or near this circle to be tall enough to reach sunlight even during the six-month polar night.

The range just out of sight from the point where the Tumblesauce had landed was, therefore, the "Mountains of Eternal Light" in which Tumble had been so interested. The question now was whether he had realized this fact, and gone on foot to see them. The trail he had left suggested that he had not; it pointed only a little north of west (not the astronomer's west, but the actual sunset direction) and would not come in sight of the mountains at all if it continued as it started. Since the surface of the moon was far from smooth even where there were no actual ranges, it seemed unlikely that the boy would have been able to distinguish the genuine peaks on the horizon from lower hillocks closer to him, even if he had barely come within sight of the range.

"But why did he go off in that direction?" asked Dart, reasonably enough. "There doesn't seem to be anything interesting that way, and it certainly doesn't lead anywhere—"

"It's pretty much toward the sun, now," pointed out Peter, "but it couldn't have been when he started."

"Why not?" asked Bowen. No relay of this was necessary, since Peter and Dart were still in the latter's ship. "We don't know when he started. He might have realized that the sun was going to set soon, and decided he'd better stay in sunlight."

"But why should he do that? He could keep warm enough in his ship even after sunset, and you'd think he'd know that we could find the ship by radar even in the dark."

"I don't know, Bart. I can't even guess. The only reason I can see for his leaving at all would be that he had some reason to think we'd find him more easily wherever he was going. That would mean the Mountains of Light, and you say he didn't head in that direction."

"We didn't follow his tracks far, though," pointed out Dart. "They were leading toward a nearby hill. Maybe he simply climbed it to see the countryside better."

"Then why hasn't he come back by now? If he were anywhere in the neighborhood he'd have heard our radio conversations—the suits and the rockets are all on the same wave length just now. He would have seen you boys landing, for that matter. No, he kept on going; it seems that someone had better find out just which way and how far. I suppose the footprints can't be seen from above unless you fly too low for safety

"And if you fly low enough and slow enough, the jet wash will sweep dust and footprints away anyway," pointed out Peter. "There's bare rock all around the three ships down already, for a good deal farther than footprints show at all clearly. We'll have to follow on foot."

"All right, see how far you can get before sunset," returned Bowen. "The two of you had better go together. Keep in touch." The boys promised to do so, and left Dart's rocket once more.

It took only a few minutes to reach the top of the hill, though the trail was harder to follow on the slope. The dust was much thinner, and in many places patches of bare rock showed. In spite of the lack of air, and resultant lack of wind, the dust apparently got downhill in some fashion. At first, it appeared that this would merely slow down the job of trailing, but when the hilltop was reached they could see that matters were a good deal worse. On the far slope, the general surface was much rougher. The dust had drifted into the numerous hollows, and even Dart admitted that the hollows were just the places where a person would not walk—at least, as long as the ridges of bare rock projected above the dust where they could be seen. Tumble apparently had felt the same way; they lost his trail on the downhill grade, and a quarter of an hour's careful search failed to recover it. Eventually they reported this fact, and asked for further suggestions. The answer came from Bart, rather faintly.

"I'm relaying both ways, now. The station has gone below your horizon, so they can't hear you. I've gone up to keep in touch with them, but I can't go much higher and still have you hear me. I think you'd better get back to your ships and at least get up where we can talk more easily—it will probably be better to get back to the station until it comes around again, anyway."

"But the sun will have set here by that time!" exclaimed Peter. "He couldn't possibly live through two weeks of darkness—he'd starve, freeze, and everything else during the moon's night."

"But he's probably not going to be caught by night. He'd only have to go a few dozen miles to stay in sunlight—he's close enough to the north pole, isn't he?"

"I suppose so. But how are we going to find him? We'd have to start our search from here, and I can't see going over this country by flashlight. We've got to stay until we find out where he's gone."

"It seems to me you've already found out all that place can tell you. Uncle Jim is agreeing with me; he says to come back. He thinks Tumble must have made a try for sunlight, and probably for his Mountains of Light where he could be sure of getting it permanently, but that you'd never be able to trail him all the way anyway; the sun will go down. The thing to do is get over to those mountains and search there. If he didn't make it, we couldn't find him anyway."

"All right. We'll head back to the ships." Peter was by no means resigned, but could think of nothing else to do; he realized that Bowen was perfectly right. The two boys trudged back up the hill until they were in sight of their rockets, and turned for a last look across the rocky waste where Tumble must have ventured. If they only knew why he had gone the way he did—

Peter eyed the line of footprints, standing out as black marks under the nearly horizontal sunlight, leading from near the hulk of the Tumblesauce to the point where they were lost in the shadow of the hill. It was too straight; Tumble had not been walking around sightseeing. He had had a goal in mind. Maybe it was the hilltop where Peter was standing, of course, but maybe it wasn't. He shook his head at the mystery, and started down the slope toward the ships, with Dart at his heels.

As they went, they waded deeper into the hill's shadow. The sun had not gone down very far since they had climbed it earlier, but that little was enough to turn this slope from dull-colored rock to a nearly total darkness, the surface lighted only by reflection from a few hilltops ahead of them that still caught the sun's rays. Peter wondered whether the shadow was deep enough to bury them completely near the bottom, and was rather pleased when he found that it was. He had not been really in the dark since landing, and with the sunlight off his helmet there was quite a difference. He could see the stars again

"Dart! Bart!" Peter stopped suddenly.

"What is it?" The question came from both brothers at once.

"We should have thought of it. I know why Tumble went the way he did. He didn't have any map!"

"So what? Why should that make him go one way rather than another?"

"How did he know which way was north? He knew the Mountains of Light were near the pole, but what good did that do him?"

"He did just what I'd do, probably—use the stars. You can see 'em, can't you?"

"I certainly can. That's why I know what he did. How would the stars help?"

"Well, the North Star is easiest—o-o-h-h!"

"Right. You get it. Polaris isn't the North Star for the moon! It must be over twenty degrees off, and this near the pole it could even be south of you. We'll be right up; get someone in the station who knows some arithmetic to start earning his keep—have him find out where our North Star would have led Tumble during the last thirteen or fourteen hours!"

PETER ACTS

WITHOUT caring precisely where he went, as long as he followed in general the direction taken by the station in its orbit about the moon, Peter sent the Ion leaping upward at two gravities. Dart had already taken off; there was no need to wait to make sure that the younger boy would not have trouble with his ship. This was just as well, for Peter was in a hurry.

It never occurred to him to doubt that his idea was right; he was too sure of his knowledge of Tumble and his ways. The only question in his mind was how quickly the men at the station could decide on the redhead's whereabouts, so that the scouts could start searching the area in question. Within a minute of take-off he called Bowen, in order to find whether the Ion was in line-of-sight contact with the station, and almost at once he received an answer. The station was not far around the curve of the moon from his starting point, and it is possible to move a long way in a short time at two gravities acceleration.

"That was a good thought, Pete," Bowen said as soon as contact had been established. "We are trying to figure out your little problem right now. It would be simple enough, except for the fact that we don't know how fast he would be able to travel; the slower he goes, the sharper the curve of his path will be, since Polaris will move farther for each mile he travels."

"I can see that. Maybe Dart and I could go twice as fast as our ordinary walk on the smoother ground while we were searching back there, but of course there's no way to tell whether all the ground Tumble will be crossing is as easy to cover. Besides, sooner or later he might realize that Polaris is fooling him."

"True, but if we assume that, we're licked before we start. All we can do is suppose that he keeps heading for that star, and guess at how fast he can go."

"You say that the problem itself is easy? How long do you think it will take them to get an answer?"

"Just a few more minutes. We can have his probable path on a map long before you can get here."

"Then I'm going to stay out, if you don't mind. You can tell me the course, and I'll plot it on my map; then I can get down again and start searching."

"Do you have a map? I thought yours had been ruined when you took them outside."

"Darn it, that's right. Hmmm. I guess I'll have to come back to the station after all. I'll go right out again, though, if you'll let me, Uncle Jim; I don't think we should waste any more time than we can help."

"We'll see when you get here. It will depend on how badly you need rest and food—or rather, how badly I think you need them."

"Well—all right. I'm coming. Is the radio beacon on?—never mind, I see it is. I'm on my way."

With the acceleration Peter was using, it did not take him long to reach the station, but he was some time getting aboard. He could not solve in his head the mathematical problem of meeting the moving station with a moving ship so that both had the same velocity when they met; he passed close several times, but was either a trifle off speed or a trifle off position. The "trifles" in each case amounted to several hundred miles an hour or several dozen miles of distance, and even Peter's usual calmness was wearing thin by the time he had his rocket hanging apparently motionless a few hundred feet away from the station. Getting in step with its rate of spin and setting the little ship into its dock presented no difficulty, since he had had to solve those problems after nearly every flight he had ever made, so a few more minutes found him eating a hasty meal while Bowen produced the map the mathematicians had marked.

It showed the range which terminated in the Mountains of Light, and a surprising number of the smaller hills in the area. It was easy enough to see where the rockets had landed; from here, several lines had been drawn representing Tumble's possible routes, assuming different speeds. They all started in the direction Peter and Dart had given and curved more or less abruptly to the right. The sharpest curves represented the slowest travel, since the moving "North Star" would turn him about half a degree an hour regardless of how fast he walked. Each line had an "x" on it to show the position corresponding to fifteen hours' travel, but the lines had been carried farther to allow for search time.

Several of the "fast-travel" lines reached a range of mountains about ninety miles from the landing point, which extended almost directly across them and pointed roughly toward the pole; several of the more curved ones reached the walled plain next to Shackleton which actually contained the pole. It was possible that some of the hills bordering this plain might be mistaken for the Mountains of Light by Tumble, according to a note on this part of the map. Peter looked at this for a long time.

"That's a lot of square miles," he said at last.

"I know," replied Bowen gloomily. "It's a lot better than the whole surface of the moon, though. Where do you plan to start? While you search, of course, he'll be getting farther along; and you can't go back for about twenty hours." Peter stared at him, but saw that argument would not help.

"Don't I know it. Of course, the farther along I start, the wider the area he may be in. I'm going down as close as I can to the place we lost his trail—"

"But that will be dark then!"

"I know. That's why I said 'as close as I could.' I'll check for level areas where there should be dust that he'd have to walk on, and if and when I find any which seem to go across all the lines on this map, I'll land and look for his trail again."

"That seems sensible."

"What are Dart and Bart going to do?"

"I don't know. They're not back yet, and I haven't had a chance to talk to them."

"Do I have to wait for them when I go?"

Bowen looked long and thoughtfully at Peter. He trusted the young fellow's ability, and realized how he felt about Tumble—the friendship growing between the two had been obvious enough to everyone. Still, there was a great deal that no one knew about the moon, and certainly there must be dangers which no one had foreseen or could foresee; times might come when even the most careful and thoughtful person would need help. On the other hand, there was the danger to Tumble, a danger growing greater with each hour that passed—he could not possibly have any food, and could not have eaten it if he had. All these thoughts crossed Bowen's mind, and Peter could read them as though they had been spoken aloud. He would not have blamed the man for refusing permission for him to go alone, but to his relief Bowen finally said:

"Go ahead—a little early, if you want. If the station is above the horizon at that place within an hour or so of the time you get there it will be all right. When the boys finish sleeping I'll decide whether it would be better for them to join you or search other areas, but I don't want them to go out without enough sleep. Check your ship, and go on."

"Thanks, Uncle Jim." Peter said no more than that, but Bowen knew how he felt.

Peter deliberately tried to sleep for the next ten hours, in spite of his worry about Tumble. The rest of the waiting time he spent eating, resting, and studying maps. When at last it was possible—or rather permissible—to return to the surface, he himself checked the Ion, donned his space suit, and launched the little rocket almost without thinking; the search problem was the only thing that held his mind. For a little while after the start, of course, he did have to think, for navigating a space ship is not quite like driving a car or even an airplane, but he knew the distance he had to go and the speed of the station around the moon, so that it did not take him very long to solve his power-and-direction problem.

He used only one gravity this time, since more would not save much time and would get him tired before he could even start his search, but even with that acceleration it was not long before the Ion was hovering above the moon's surface very close to the point Peter had selected. This was not where the rockets had landed before; as Bowen had said, the sun had set at that point. In that direction was darkness, where the bulk of the moon cut sharply into the background of stars, with a few bright spots where hilltops reached up into the sunlight.

This sketch map was copied from the photo maps made at the station when we first approached the moon. I simplified it by leaving out a lot of unimportant details, to make it easier to read.

(1) is where Tumble landed. The arrow shows which way he started out, and the dotted lines show the courses the mathematicians at the station thought he might follow. (2) is where I landed to start the search; the ridge where his trail first appeared is at (3). The arrow there points to the part of the Mountains of Light which could be seen; the closer part of the range is hidden by a bulge in the moon's surface —what a geologist would call a "dome." Tumble says that somewhere near (4) he figured out where he was. You can argue that out with him. The circle at (5) surrounds the two big peaks which Bart and I searched.

The dotted line near the top of the map indicates where the sunset line would have been at the time of the eclipse. The only reason Bart and Dart could see the sun and Earth at that time was that their ships were parked on unusually high ground.

PETER L. ASHBURN

Below him the shadows were long, some reaching completely beyond the sunlit regions and looking like notches in the moon's edge. The surface looked far rougher than it really was, and Peter had a hard time deciding whether any of the areas below were smooth enough to show a trail. He sent the Ion drifting, tail down, several miles in each direction, but at last he realized that he would have to land even to find likely spots to start his search.

He checked his map against the landscape below, found a spot a trifle to the south of the lines which represented—he hoped—Tumble's probable courses, and let the Ion settle slowly. On the ground with his power shut off, he wasted no time; he checked his suit and went out through the air lock. Keeping the sun on his left, he began to walk away from the ship; as he went he examined the ground minutely for tracks. Occasionally, with no real hope of being heard, he sent out a call for the missing boy on his suit radio.

The ground was fairly level, though it had been hard to be sure of that from above. The dust lay everywhere, though it was never more than an inch or two in thickness. Usually when he kicked it, it settled back to the surface at once, like the bow wave from a ship—it looked a little weird at first, though Peter knew that with no air to speak of there was no reason for even the finest dust to float any longer than gravel. Occasionally some of it did stay up a little longer, and at times there were faint bursts of static on his suit radio. But he was too thoroughly occupied with his search to devote any thought to these occurrences, or even to wonder whether they might be connected in any way.

Peter did not keep very close track of how far he went; he returned to the ship twice for food and rest, each time finding his way back easily enough by using his own footprints. There was no risk of the ship's being hidden by darkness. On Earth, in the latitudes covered by the United States, the sun would have sunk below the horizon in a few minutes from the point where the Ion was parked, but on the slowly-turning moon, this close to the pole, the ship would be in sunlight for many hours. Therefore, Peter did not worry about time.

He naturally left the maps on board, and was directing his course by memory, but after several hours on his third trip he felt sure that he must have gone well past any point where Tumble was likely to have been. That raised a rather serious question: had the redhead changed course so sharply that the mathematicians in the station were completely wrong? Or had he kept on going, but traveling on bare rock with no dust covering, at whatever point Peter had crossed his trail? Peter did not think the latter was likely; he had encountered a few slopes whose sides were clear of dust, but in each case he had followed their borders to the end so that 206 he would find any traces which might exist of Tumble's leaving the bare surface.

There was another possibility, of course; Tumble might have kept his direction as long as he could, but still failed to get even as far as Peter now was from the point where he had started. In that case, of course, he should have been able to hear the radio conversations going on during the first landing—and also in that case, he would now be lost in the blackness of the moon's two-week-long night, with the temperature around him dropping close to one hundred Centigrade degrees below zero and no sunlight to operate the air renewing equipment in his suit. His batteries, of course, would operate his heaters and air apparatus for a while, but certainly not for two weeks.

In that connection, a thought suddenly struck Peter, and he spoke into his radio.

"I'm away from the ship and won't be able to hear your answer, but you should be able to hear me, Uncle Jim. How about checking the dark part of the moon around where Tumble landed with infra-red equipment? If he's alive, his suit will certainly be a lot warmer than the rocks around him. I know the observatory in the station has all the equipment you'd need, and it shouldn't take very long.

"I'm going to turn back to the ship and move it to another center as soon as I reach the ridge I can see ahead of me. I'm well past the farthest of the lines on that map, unless I've been traveling far slower than anyone thought Tumble would." He did not wait for an answer, which he would not have been able to hear anyway, but headed on toward the ridge he had mentioned. When he reached it, however, he had to change his plans.

It was higher and steeper than those he had crossed before, and much freer of dust. It was obviously possible to walk along it, in the direction in which Tumble was supposed to be going, and stay on bare rock, and Peter had already found out that staying on bare rock made traveling easier. The dust, he had found, tended to cling to the plastic suits, as dust on Earth did to the plastic "housecleaners" which were so popular with housewives—probably for the same reason, static electricity. On legs and body it meant nothing, for its weight was negligible; but on the supposedly transparent face plate of a helmet it was a serious nuisance, since the stiff gloves of the space suits were not at all suitable for wiping.

It could be taken for granted, therefore, that Tumble would have followed the ridge if he had come this way; in that case he would have left no trail. Peter looked both ways thoughtfully.

To his left, toward the sun, the ridge went on until it was hidden by the near horizon; in the other direction, it seemed to get lower and merge with the more level surface. Peter decided to go right, since there seemed a better chance of finding dust-covered ground there, even though Tumble had presumably been going the other way. His judgement proved right; within two miles the ridge had flattened out almost completely, and once more the patches of dust spread until they covered the whole surface.

Peter had just barely started across what was left of the rise when he found long grooves in the fine powder —grooves which formed a nearly straight line, pointing off toward the dark side of the moon. There was no doubt about the cause, for his own boots had been leaving just such grooves for several hours. In walking under the feeble Lunar gravity, one did not bother to pick up his feet very far; motion was more of a glide, in spite of the clumsiness of a space suit.

"Uncle Jim! I've found the trail—I can't give you the precise position now; I'm going back to the ship, and bring it over here with the maps."

"Don't bother." It was Bart's voice. "We're somewhere above you now, in range I should think. Let me know if you hear me." Peter complied. "All right. Keep broadcasting; I'll home down to you with the radio compass."

Ten minutes later two rockets settled to the top of the ridge, half a mile from the point where Peter was standing; and the next stage of the hunt got under way.

MOUNTAINS OF LIGHT

ALL three boys gathered in the Outbound, and held a consultation over the maps. After some argument via radio between Dart and his uncle, they decided where they must be; and it was evident that Tumble had either traveled more slowly than any of the mathematicians had expected, or had not been following Polaris. He had passed closer to the actual pole than anyone had expected. A row of peaks was just visible at the horizon from the control room of Bart's ship, and this was apparently the nearer end of the range whose farther tops formed the Mountains of Light—a fact which Tumble, of course, would have had no way of knowing.

The ridge on which the rockets stood had, the boys supposed, served as a path for Tumble. It was impossible to say just how long ago he had passed; the ground offered only the simple evidence that he had.

"I suppose the only thing to do is go to the other end of this ridge and pick up the trail there," said Bart. "I wonder how far he's likely to have gone? I suppose there's only one way to find out."

"I'm not sure of that," said Peter slowly. The brothers looked at him in surprise.

"What do you mean? How would you check?" asked Bart.

"I think we've been taking too much for granted. We've been supposing that Tumble found he couldn't fly his ship, and went steaming off in search of the Mountains of Light without any particular reason in mind. I know he's a bit hasty at times, but I think we've not been doing him justice.

"For one thing, I think he must have thought out very carefully the question of whether we would be coming to look for him or not. We know he doesn't trust us fully, but if he had decided we weren't coming he'd have stayed in his ship—at least, I would expect him to. He'd live longer there.

"If he expected us, then there's some reason behind his going where he did—"

"I know," interrupted Dart. "We've already supposed that he would be heading for the Mountains of Light —I don't see that it matters if he was going there because he wanted to see them, or he needed constant sunlight to keep his air supply up, or figured we'd be most likely to find him there. The important thing is that he didn't start out for those mountains, but in a direction which would take him miles to their left; and we've just found that he held the direction pretty well —at least, up to here he hadn't changed it enough to hit the mountains."

"Just the same, I think he's somewhere in that range right now."

"Wha-a-a-t? Are you sure your brains didn't get dried out along with your maps a while back?"

"All right, you tell me why we haven't heard a call from him—or better, why the station hasn't. He can't possibly be out of range just by distance; there's something in the way. Look at this map; in the direction the mathematicians thought he was traveling, he might be in this other range here." He pointed out the one he meant. "The first catch to this is that if those mountains are the ones which were blocking his transmission when we first arrived, he traveled a good eighty miles in less than fifteen hours."

"He wouldn't have had to get that far to be blocked from us; the horizon is pretty near on the moon."

"From us, yes; but the horizon wouldn't have shielded his waves from the station. He'd have to be in a pretty narrow valley somewhere for that."

"Well, why not in that range? Anyone can travel over six miles an hour on the moon—we found that out for ourselves."

"A person can, yes; but would he travel eighty miles practically nonstop, with no food, even on the moon? Tumble might have been in quite a hurry, but I doubt if it was that big. Besides, we've just found that he didn't stick to the course the mathematicians thought he would; he went farther to the right, if we're where we think we are. If he kept bending like this, he'd never hit that range at all—he'd wind up at the rim of this walled plain that holds the north pole. He'd know that that wasn't the place he was looking for. Tumble has watched this part of the moon too often and too closely to mistake even a forty-mile crater for the Mountains of Light, hard as it is to tell the difference from Earth. Remember, he got better looks at it than anyone on Earth ever did when he was using the telescope in the station.

"I think that somewhere along his route, probably not too much farther along it than we are right now, he found that he was heading the wrong way and managed to correct course."

"But how could he have known it here?"

"I don't know, but I haven't seen as much of the neighborhood as he must have. He's no mathematician, but maybe the motion of the sun gave him a clue; maybe he suddenly realized that there was no reason to expect the regular North Star to work here, and headed for the first mountain range he saw after that. He could see the Mountains of Light from here, too; at any rate, we can!"

"Hmph. Then what do we do? That spreads out the field of search an awful lot."

"What I'd like to do is travel on foot along the side of this ridge toward the mountains, to see whether Tumble left it at any point to go in that direction. If he didn't, then he must have kept along the ridge the way he started."

"We don't really know that the tracks down here were made by him coming toward the ridge," Dart pointed out. "He might have been going away, instead. Those grooves in the dust don't tell a thing about which way a person is going."

"That's true," admitted Peter, "but it seems a little queer that he should be heading away from the sun."

"Maybe he was trying to go back to his ship."

"He should have known it would be in darkness by now."

"We don't know when he passed this way; maybe it was before sunset at that point."

"Then why didn't he use his radio? We were at, and over, the site of the landing until awfully close to sunset time."

"I suppose that's so. I'd kind of like to check up on the Tumblesauce just now, though; we'd feel pretty silly if he was back there all the time."

"If you can think of a way to find it in the dark, go ahead. Just the same, I'd like to make the walk I just mentioned; and I think one or both of you should fly along to the far end of this ridge, to check whether he left it there. If he didn't, maybe one of you could walk back along each side; then we'd cover the whole thing, and know where he left it—or if he's still on it."

"I think that's the best plan," Bowen cut in from his distant listening point. "Just one thing, first. Peter is several hours' walk from his ship. One of you should fly him back to it, so that he can bring it closer to the area where he is searching. Then go ahead as you've outlined."

This seemed a sensible point, and the boys wasted no time following it. Dart returned to the Jabberwock and took off along the ridge, while Bart, directed by Peter, went in search of the Ion. It was easily found—for one reason, the sun was so low that even Peter's set of footprints cast a shadow which could be seen from overhead as a straight, black line running across the face of the moon, as easy to follow as a railroad. Two or three minutes' flight brought them to rest beside the Ion, and Peter gladly went back to his own ship. He had no objection to the way Bart flew, but he was happier in a rocket which he himself was handling. He took off at once, returning along the line of footprints they had just followed, while Bart used his radio compass to home toward his brother's rocket.

Peter tried to plan out his time as he flew. If he landed where he had found Tumble's prints and started walking as he had planned, he could count on perhaps five miles an hour. He could get the distance to the other end of the ridge from the other boys, who must be there already—at least, Dart must be, unless it was remarkably long. The map did not show it; it had been lined up so nearly with the direction of the sun when the original map photos were taken that its shadow did not appear on them.

There might, of Course, be delays; in several directions he could see long lines of black on the surface which might be fairly deep cracks, though he had been lucky so far in his walking and had never come across a crevasse deep or wide enough to stop him. Perhaps he had better drift along over the route of his planned walk first, though; if there were any very wide ones, he could plan to leave the rocket near enough to them—but no; none of them was likely to run far enough to prevent his getting around them by a short climb. The few he had met in his first walk along the ridge had always stopped before the ground rose very far. He decided to let things come without too much planning, and settled toward the place where the trail of the missing boy met the end of the rise.

There were cracks, at that; one of them was in a rather annoying position, leading away from a point near the end of the high ground, perhaps half a mile from where Tumble's tracks showed and angling off toward the distant Mountains of Light. That meant that if Peter were to cover all the possible places where Tumble could have left the ridge there would be a delay almost at the beginning, for he would have to start at the trail and go only half a mile before having to climb around the head of the crevasse. He was tempted to skip that half mile; after all, what were the chances that Tumble would have left the ridge so soon? Besides, he should be able to see any trail going toward the Mountains of Light; it would be heading across the sunlight, and should cast as sharp a shadow as his own."

Peter almost let the rocket drop the remaining two hundred yards to the ridge as he suddenly realized where his thoughts were leading. He did make the hardest surface landing the Ion had experienced so far; it was lucky that the boys had been leaving their landing "legs" extended during all their short flights near the moon, for he would almost certainly have forgotten to put them out, and in consequence been marooned just as Tumble had been.

He broke all records for getting out of the ship, though even in his excitement he did not forget to check the airtightness of his suit. He did not examine, the half mile of ground between the trail and the crevasse; he headed straight for the latter as fast as he could travel. That, going downhill and in a gravity where he weighed less than forty pounds complete with space suit, was quite fast.

As he approached, the fine black line grew more distinct but less regular. Even before the real details were visible, he knew what he was going to find; but he didn't dare make a report until he was at the foot of the ridge, where the dust started again. There he saw clearly before him, stretching toward the horizon and the Mountains of Light, the line of shallow grooves in the dust which were Tumble's footprints. The mountains themselves were not visible from this level; the redhead must have seen the peaks from the top of the ridge, and somehow guessed what they were. At any rate, he had certainly gone toward them.

Peter was leaping back up the ridge toward the Ion as he called the other boys. There was no answer from them; they must have landed, and the radio waves were cut off by the horizon. It did not matter; the people in the station must be hearing him, and he could get in touch with the boys as soon as he had taken off.

He went inside as rapidly as the tiny air lock would let him, and fed power to his main drive almost before the inner door had closed behind him. Three seconds later he was following the thin line of black toward the mountains, giving most of his attention to keeping it in sight while he made a detailed report into his ship radio. Bowen acknowledged at once, Bart and Dart a few moments later. They had just been getting out of their ships, and had not heard him at first. They hastily got back in, and took off toward the mountains.

Peter followed the trail as far as he could and as well as he could. Twice there were breaks; apparently low ridges, bare of dust, had crossed the boy's path, but he had not followed them. The trail went on in a straight line after each interruption, toward the mountains.

But not to them. Tumble had been heading that way, that was certain. Maybe he had made it; but at the lowest slopes of the mountains the sun had practically set, only a tiny rim of its bright disc remaining above the horizon. Every tiny irregularity in the ground cast a shadow far longer than itself, breaking the landscape up into a pattern of dead-black streaks interrupted by narrow areas that looked bright by contrast in spite of the low sun and the actually dark color of the rock. The higher parts of the range looked blinding for the same reason, where they thrust upward into full sunlight.

For scores of miles that line of bright saw-teeth extended, points of light jutting from almost invisible bases. If Tumble were here, he must be well up one of the mountains by now—or trying to get up. He would know that only on the peaks would he get the steady sunlight his air purifier needed. But which peak would he have tried for? If he still did not answer to radio, how could they all be searched? Bart's voice came through the receiver, summing up the situation.

"I guess we get our first mountain-climbing practice in the dark!"

NO EXIT

"ALL of you! Hold your ships where they are, as nearly as you can manage!" Bowen's voice snapped from all three radios. The boys wasted no time in questions; Uncle Jim seldom used that tone. Each of them brought his rocket into a tail-down attitude and adjusted his power to offset the moon's gravity; then they checked drift, and tipped far enough to reduce any speed they might still have to zero. Peter, who was going fastest when the order came, was the last to report that he was stopped.

"All right," came the answer. "Now, I suppose Bart and Dart started from one place and Peter from another, and all headed for those mountains; is that right?" The boys admitted that it was. "I thought so. You were a good many miles apart, and couldn't see each other. You still can't, I suppose." Again he was right. "Then do some thinking—all of you. I know you're used to the idea of shooting around at fifty miles a second or more, at least on long trips; but please remember that if one of those machines hits another at a relative speed of even fifty miles an hour, there'll be nothing but a ball of tinfoil somewhere on the moon. Now get together where you can see each other's ships before you do anything more about searching. Peter, you should be closest to where you all want to go; turn up your transmission so that they can home on you. Dart, you go first while Bart stays put; then report when you see Peter's ship, so Bart can start."

"Yes, Uncle Jim." The boys were a trifle sobered by Bowen's words; Peter spent some time figuring out how long there would be for the pilots to dodge if two rockets approached each other at a mile a second, were not noticeable to each other at more than half a mile, and the pilots each had a reaction time of a tenth of a second. The answer made him uncomfortable.

Several minutes passed before the three rockets hung side by side perhaps five miles above the moon's surface; then the question arose of just what should be done next. Tumble's trail had been hopelessly lost, as far as being spotted from above was concerned, in the pattern of shadows at the foot of the range. It might be followed by a person on foot, even in the darkness where the sun did not reach; but there was the new certainty that the moment the boy had started to climb he would have been on bare rock, and leave no trail anyway. There was no point in trying to bring a rocket low enough to check that point; aside from the danger of flying among the peaks, the jet stream would, as Peter had said, blow away the dust which held-the footprints.

"It looks," Peter remarked, "as though you were right, Bart. We do some mountain climbing. I suppose we'll cover the place fastest if we take a mountain apiece—"

"I hope I didn't hear that correctly," came Bowen's voice. "I don't much like your climbing mountains in space suits as it is, but you're there and I'm not; if you think it's the only way, I suppose it is. However, one of you stays in his ship so that messages can get from me to you—I know I can hear you all right, but that's not enough. Also, you will climb only when the station is above the local horizon; the rest of the time, you come back here to eat and rest. I know that will cut over fifty percent off your search time, but that's the way it will be. Now, who stays with his ship?"

All three names sounded at once, though they were not spoken by their respective owners.

"All right, you all want someone else to stay. I'll settle it to save time. Peter goes, because he knows Tumble best and is most likely to get ideas about what he'd do on a given spot. Bart goes, because he had to stay with his ship last time. Dart, it would be best if you took your ship up ten or fifteen miles, so that you'll be above them and there won't be so much chance of a spur of rock cutting off radio contact."

"But Uncle Jim—"

"Save it! You agreed that I was the commander, and you were my eyes. You're sharp youngsters, but you still let things interfere with your judgement. As long as that happens, we'll use mine. You're wasting time, Dart."

"Yes, Uncle Jim." Dart added power enough to send his rocket drifting upward without further argument, while the others let down toward a more or less level spot fairly close to the foot of the range. It was not level enough, as it turned out, except in very small areas; Peter had to hold a few feet off the ground while he directed Bart in to a landing. With his power off, Bart then returned the favor. It would have helped a great deal if the pilot were able to see directly below his ship while it was in landing position.

Both boys got out and looked around. Only a tiny sliver of the sun was visible; most of the ground could be seen only in the relatively faint light reflected from the peaks. Walking would be treacherous; it would not be easy to tell whether a dark patch was a shadow across a two-inch-deep hollow or a fifty-foot blowhole. The ground was definitely volcanic, or what would have been called volcanic on Earth; irregular masses of rock not only contributed to the shadows but suggested unpleasant things about what might lie in a shadow. A spur of sharp lava, unseen until one walked into it, might puncture a space suit. Flashlights were a necessity, and travel would be slow.

"Might as well start," remarked Bart after a few moments' examination of the surroundings. "Any preference on mountains?"

"Yes. I'll take this on my side because it's the tallest in this part of the range, and it and the one beside it are closest to the line Tumble was taking when we last saw his trail. I think he'd take the high one to be surer of sunlight, but we'd better cover them both to play safe. You take the other one. We have a few hours before the station sets; we'll cover what we can of these hills. Keep using your radio; if Tumble's silent just because he's cut off, you never know when we'll be in position for him to hear us."

"Right." They started without further discussion.

The climb was even harder than they had expected. There was no possibility of standing on a high point and looking over a large area at once; any black spot one could see might be deep enough to hide a space-suited boy, particularly one Tumble's size. Every square yard must be covered. Peter did not let himself figure out the number of square yards; he didn't want to get discouraged any earlier than he could help.

Sometimes there were patches of dust, caught on level places or in hollows on the slopes; but there was never a trace of Tumble's passage in any of them.

The only thing which made the task possible at all was the lack of erosion on the moon. The mountain was still much as it had been when it was first formed; only spalling by the fierce solar heat had softened its outlines a' trifle. There were no gullies, such as a stream would cut in a mountain on Earth; no potholes such as a glacier might leave; no dunes such as wind might pile.

There were occasional crevasses, and deep holes which looked as though they had been blown by gases escaping from still plastic lava; Peter sent his light beam probing into each of these that he found, but all were empty save for the dust, which seemed to be everywhere on the moon where it could settle. He felt a little uncomfortable when he reflected that the light of his flash was probably the first thing to disturb these holes, or some of them at least, for millions of years. Even some of the dust clung to their walls instead of working its way to the lowest level, as it had done out on the surface.

The sunward half of the mountain had been covered better than Peter had expected by the time Dart relayed the call to return to the station, but there was still a lot to be done. The searchers obeyed the order; back at the hunt some twenty hours later, they admitted to themselves that they were better for the food and rest, even though the wait had been long.

Dart had suggested putting the station into an orbit which would not take so long to get it back into sight of the Mountains of Light, but before Bowen's marrow had had time to chill at the thought of more maneuvering, Peter had pointed out that any such orbit would mean staying in sight of them for a much shorter time, as well. Right now the station, more by accident than design, was in a path which did keep it in sight of the north polar regions more than half the time, which was a pretty good compromise—to do that, its path had to take it a scant two hundred miles above the south pole of the moon, while it rose some eighteen hundred above the north.

But even twenty-odd hours above the horizon was not enough, in one way. The boys, naturally, could not search that whole time; they had to return to their ships to rest and eat, resenting every minute so spent. Tumble had been away from his ship for something like four days; the longer it took to find him, the less were the chances of finding him alive. None of the boys had ever been really hungry, but they were able to guess vaguely how Tumble must be feeling by this time.

As the search period wore on, and the sun drifted farther and farther around the horizon without getting lower, Peter in particular began to feel the hopelessness of the situation. He had never been a quitter, but at the rate they were covering the range he could see all too clearly the length of time it would take to finish the job; by no stretch of his imagination could he see how Tumble could live that long. It seemed likely that the boy would have climbed the first really high peak he found after reaching the range; but had he?

Peter took to staying out on the mountain longer and longer, dashing back to the Ion occasionally for a bite to eat, but not getting any rest to speak of. Even Dart suggested that he might search better if he took more care of himself, and offered to take his place while Peter remained in his ship and served as relay man; but the usually sober and thoughtful Ashburn scarcely thanked him. He was almost mad with worry; he took to using the earth as a timepiece. It had been well away from the sun when they had first found the Tumblesauce; much closer when Peter found the trail to the Mountains of Light; now it was only a few degrees away, showing as a thin crescent cut by the horizon in the same way as the sun. All the boys knew that the station would go below the horizon before the earth actually became "new"—that is, before it passed as close as it would to the sun—so Peter's keeping an eye on it was not entirely senseless.

It grew ever thinner and closer, and Peter grew more and more frantic. He wanted to travel faster—to cover more territory but he didn't dare skimp on his examination of the ground herd id cover. This mountain must be the one, if he knew Tumble at all.

Over hillocks—through crevasses—up and down slopes—peering into each blowhole which could possibly hold a space suit—checking each shadow to find whether or not it concealed a hole or a body: the boy became virtually a machine; he would sometimes have to be called two or three times by the relay man before he roused himself enough to answer. Peter was searching automatically; almost the only thought in his mind was, "Will I find him first?"

He didn't—quite. Dart was back on relay duty—he had traded with his brother, for a while—by the time the station approached the horizon, and it was his voice which Peter heard. The words hardly meant anything to him; he didn't hear, "I'm afraid we'll have to cut off for a while, fellows; Uncle Jim says it's time to get back to the station," but rather, "You lost. You didn't look hard enough; you didn't think fast enough; Tumble's gone." It didn't occur to him to disobey Uncle Jim's order; he turned dully downhill, and almost fell into another blowhole.

As a matter of habit he speared the beam of his flashlight into it, and froze where he stood. Space suits are not made of metal, but the plastic is still very different from the dark-colored rock which covers most of the moon, and there was no mistaking the object which could be seen far down the narrow, slanting shaft. It lay about thirty feet below him, motionless, and without a single thought about the advisability of the act, Peter stepped over the edge.

He was several feet down before it occurred to him that, while a drop of thirty feet on the moon is about equal to one of five feet on the earth and can be taken without much trouble, the man who can do a standing high jump of five feet—that is, one which will raise his center of gravity five feet—is a rather unusual specimen.

The person who can do it in a space suit is rare indeed. But it was a little too late for the realization to help him.

SIGN IN THE DUST

HOWEVER, the sight of the space-suited figure was acting like a stimulant on Peter. In the slightly over three seconds it took him to reach the bottom, he had recovered enough of his usual calmness to be able to push the problem of getting out of the hole to the back of his mind, and concentrate on the more immediate matter of Tumble. The figure at the bottom had not moved since he saw it; it did not move when he struck the lava beside it with a jar. Peter heard the blow, but he realized that no one else could on the airless satellite; perhaps it was that Tumble didn't know he was here.

The flashlight revealed a pale, thin face inside the helmet. The eyes were closed, and since the normal actions of breathing could not be seen through a space suit, Peter was afraid for a moment that he had come too late after all. Then the figure shifted, twisted, and the eyes opened. Tumble had simply been asleep.

"What's that?" His voice came clearly enough through the radio. Peter swung the beam of the light on his own face, and Tumble's voice rose to a yell of delight.

"Pete! You found me! How long have you been looking? How long have I been here? Where are the others?"

"Take it easy. Bart's about five miles away, scouring a mountainside for you; Dart is being radioman up in his ship. It's about five days, as nearly as we can guess, since you left your ship; you know better than I do how long after that it was when you got yourself in here. Did you fall, jump, or what?"

"I jumped. I'd jumped off places nearly as high several times before, and knew it wouldn't hurt me; but I couldn't jump out. I—I've been scared, Pete. I'm hungry, too."

"That I can believe. We'll have you into a ship and eating before too long—I hope."

"What do you mean, you hope? Can't we get out now?"

"I don't suppose I can jump any higher than you can."

"Then call on the radio."

"They won't hear us; the rock cuts off the waves. That's why you haven't heard us talking the last few days. Still, with two of us it should be possible to do things that neither of us could do alone. Let's do some thinking."

"You don't have a rope?"

"I'm afraid not. There wasn't a suitable one at the station."

"And anyway, I suppose when you left the station you didn't know you'd be mountain climbing."

"Yes, we knew that; that's why we looked for you. They may look harder now; I suppose Dart and Bart will have to go back without me and report. At least, they'll know about where to look when the station comes back."

"Comes back? Where is it?"

Peter told him the whole story, from the time the Tumblesauce had disappeared toward the moon; Tumble listened in silence, forgetting his hunger for the moment.

"Pete," he asked at length, "how is Dr. Bowen now?"

"In his wheel chair—they put several of them together from odds and ends at the station."

"You mean maneuvering that station put every man in it under wrong weight? They're all sick, the way Dr. Bowen was when I first was spying on you back on Earth?"

"Not all in quite the same way, but most of them are sick, yes."

"And they knew it would happen. Why did they do it?"

"I think you know the answer to that." There was another long silence.

"I guess I do," Tumble said at last, slowly. For several minutes they both thought; Tumble about the things which had happened since he had met these boys, and Peter about the matter of getting out of the trap they were in. It was Peter who spoke first.

"How much strength do you have left?" he asked.

"I don't know. I can stand up, but who couldn't here? I haven't tried to jump for I don't know how long."

"Could you still chin yourself, or pull yourself over the edge of the hole with your hands if you were to get hold of it?"

"I don't know. Hold out your arm and I'll try." Tumble got to his feet without much difficulty, and found that he had little trouble supporting himself with one hand from Peter's outstretched arm. "I can do it, all right. What good will it do us? You don't have a rope, and standing on your shoulders won't help by a long shot."

"Obviously; but suit and all, you weigh only about thirty pounds on the moon. The distance to the mouth of this hole is about thirty feet, which would be something like five against Earth's gravity, and if I can't throw a thirty-pound weight five feet straight up, something's wrong."

"Well—O.K., I guess. The sides of this hole are pretty smooth."

"That's right—but don't bash your face plate against it, just the same. All set?"

Peter had been perfectly right—he could throw a thirty-pound weight more than five feet vertically. However, there was something wrong—with Peter's mathematics, of all things. He should have figured on throwing the thirty pounds thirty feet, or else one hundred eighty pounds for five feet. He shouldn't have tried to count in the moon's gravity twice. The best result of four tries brought Tumble's outstretched gloves scraping dust from the wall within about ten feet of the lip of the pit; closer than that, Peter could not get him. When succeeding throws began to grow steadily worse, they stopped to seek some new solution to their problem.

Peter did not want to admit it, but he was getting badly frightened and was finding it harder to think sensibly. Bart and Dart knew which mountain he was on, but they might easily be longer finding him than he had been finding Tumble; it would be pure luck—good or bad, as might happen. He could reach them by radio only if one of the ships happened to get directly in line with the narrow mouth of the blowhole; the chances of that were ridiculously small. He himself might hold out for days, but Tumble couldn't; the younger boy would have to eat soon, and his batteries must be nearly discharged after several days of doing the job that sunlight was supposed to do in his air renewers. When they were drained, there were the four emergency oxygen cylinders; when those were done, so was Tumble.

"How about your light, Pete?" the redhead asked suddenly. "It seemed pretty strong when you were shining it in my eyes a while ago. Can't you use it for signaling?"

"Not unless they're looking into the hole already. If they're in position to do that, we could get them on the radio."

"But won't they see the beam if you shoot it out the mouth of this hole?"

" 'Fraid not. To see a beam like that, either you have to be in, its direct path or it has to be shining on something to reflect light into your eyes."

"I've seen searchlights on Earth that weren't pointing at me."

"I know. That's because of dust and fog and such things in the air. Here there isn't even any air—at least, none worth mentioning. We could see the jet streams of the rockets when we got within fifty or sixty miles of the moon's surface, but they pack a lot more energy than this flashlight. Besides, the rock outside the hole is in sunlight; even with air, you'd never see the beam against a bright background."

"I see." Tumble lapsed into silence. It hurt him to talk now, anyway; he had to move his stomach muscles, and his stomach was hurting steadily. He wanted to eat, but was afraid that if he did his stomach wouldn't stand it. He was even less in condition to think than was Peter.

Why Peter didn't find the answer sooner he could never explain afterward. Probably it was because he had thought of two difficulties at once—the lack of air to scatter the flashlight beam, and the bright background to hide it if it were scattered. A solution to one would mean nothing unless he could also solve the other, and the only solution to the second problem seemed to be to wait until the sun got to the other side of the mountain, ten days or a fortnight from now. That was little help.

Of course, it is possible that was not the real reason why he lay beside Tumble for several hours without having a single useful idea cross his mind, but it is at least certain that when the change in the sunlight reflected down from the lip of the hole finally caught his attention, he had a working idea ready to use in less than two minutes.

The light must have altered a good deal before he did notice it. There wasn't much to start with, of course; just the reflection from a few square feet of darkish rock. It was enough to let a person see small objects at the bottom of the hole, once his eyes were used to it, but not enough to keep him from seeing the stars which were shining in. Peter noticed the change when he finally summoned up the ambition to see how long they had been trapped, and tried to read his watch.

He could barely make out the dial mounted in the wrist of his suit, though he had had no trouble with it earlier, and that brought his attention to the mouth of the hole.

"Tumble! Look up!"

"Why?" The question was a mumble.

"The light's going! Something's going on!"

"Do us any good?"

"I don't know—look at it, will you?" Tumble was moved sufficiently to open his eyes; this was enough, since he was lying on his back.

"Getting redder—someone light a fire?"

"Don't be silly—you don't light fires without air. Anyway it's not like fire, it's more sunset color, and that's just as silly, because—no! Wait a minute! It's not silly either; it is sunset color! I see it—I know what's going on!"

"Any good for us, or just something to know?"

"Plenty of good for us. Remember a month ago there was a regular full moon—no eclipse?"

"That's right."

"And two weeks ago there was an eclipse of the sun —we watched the moon's shadow crossing part of the earth."

"I remember."

"Then there's got to be an eclipse of the moon this time around, and that means an eclipse of the sun, for us! The sun will be covered by the earth; that's what's making it get dark!"

"Why the red?"

"Same as a sunset on Earth; the light that's getting to us is going through a lot of the earth's air. If we could see it now, it should be really pretty; a big black ball with a red-hot ring around its rim. I just hope those Rangers aren't too busy watching it, and are still outside, because this is our time to signal. There won't be any bright background now—or at least, in half an hour or so when the eclipse is really on."

"There's still nothing to scatter your light beam around."

"There's plenty to scatter it. We're ankle deep in dust; we have dust still sticking to our suits; there's dust lining the walls of this pit. I may not be able to throw you out of here, but if I can't get a handful of dust above the edge of this hole, something's wrong."

"That's what you said before."

"Never mind that. Start scraping dust together. We'll wait a while, until it's really dark; then I'll prop the flashlight—no, there's nothing to prop it with; one of us will have to hold it—and we'll start throwing dust up along the beam."

"Try it now, just to see if it works. I'd like to know the worst without having to work up a worry."

"All right. Hold the light." Peter handed over the flash, and picked up a handful of dust as well as he could in the gauntlets of his space suit. Tumble held the light pointed toward the mouth of the hole, while Peter wound up and threw.

On Earth, of course, the handful of bone-dry dust would have gone perhaps five feet, forming a cloud which would gradually settle to the ground. Peter knew that it would not be slowed in any such fashion, but he had not thought at all clearly about the other effects produced by a lack of air. He was rather startled when the lump of dust simply broke into two or three pieces as it left his hand, and sailed off without showing the least disposition to spread out and form a cloud which could be illuminated by the flashlight. Tumble was startled; Peter, after a second's surprise, realized what the trouble was.

"No air to slow down any of it, so all the dust grains kept going at the same speed," he explained briefly to Tumble. "That's a nuisance. How do you throw a handful of dust so you can let go of the different grains at different speeds, but all in about the same direction?"

"Blow it off your hand," replied Tumble promptly, thereby startling Peter more than the behavior of the dust had done.

"Can't do it through a helmet—but wait a minute; you're right. We can use the emergency oxygen tanks. A half second squirt from one of those would set things going; they have over a ton to the square inch inside pressure."

"That's right. Take off a couple of mine; you know the connections better than I do."

"Don't be silly; I have days left in my battery and yours must be nearly done. You'll need the oxygen. Take off one of mine, and we'll see if it works."

Tumble obeyed, handed Peter the little tank, and resumed his position with the torch. Peter tried to manipulate the tank valve and hold the dust at the same time, but lacked sufficient hands; so he finally got Tumble to hold a palmful of dust as well. This time the procedure worked like a charm; a silent jet of gas —silent to Tumble, that is; Peter heard the hiss transmitted through the plastic of the tank and suit—struck the pile of dust and sent it upward in a spreading shower. The oxygen passed on, its speed hardly decreased, and peeled another supply of particles from the wall of the blowhole. To the delight of the two experimenters, the tiny specks of material flashed brilliantly in the light beam, and the best part of ten seconds was required for the last of them to fall out of its path.

"That will do it," said Peter. "Now we'd better wait until it's really dark; then we'll keep this up until we run out of dust or I run out of oxygen. If nobody sees it—well, we'll just have to think of something else, but we won't worry about that now."

"Not if we can help it," returned Tumble, "and I guess I've run out of worry ammunition for right now, anyway."

He must have been right, for he fell asleep while he was waiting for Peter to decide that the moment had come to start signaling.

RED DARKNESS

BART was, as Peter had said, some five miles from the mountain where Peter was searching when the recall came in. Both searchers were able to hear the relay, but at that time they could not hear each other; a spur of Bart's mountain cut off the radio waves. As a result, some time passed before anyone realized that something must have happened. It took Bart fully half an hour to get back to his ship, and only then, when he called his brother to come down into view so that the Outbound could take off safely, did the situation become apparent. Dart obeyed the call, and while he was easing down to where Bart could see him he called Peter to ask whether he was nearly at his ship. Naturally, there was no answer; and when several more calls brought no response, Dart landed beside the Ion to investigate.

The ship was empty, and no sign of a moving figure could be seen on or near the mountain beside which it stood, though the boy went over it thoroughly from his control cabin with a large pair of binoculars. Bart was calling by this time—had been for some minutes, in fact—wanting to know what the trouble was, so Dart put down the glasses and explained.

"Do you suppose his radio could have quit?" asked Bart thoughtfully.

"It could have, but he's had plenty of time to get back here even if it has. I went over to his ship and he wasn't there, and he hasn't come back since then, and I can't see him anywhere on the mountainside."

"He might be exploring a crevasse."

"He's been out of touch pretty long for that. We agreed to check in every fifteen minutes at the outside, you remember."

"That's true. Maybe he had a fall, or got hit by a meteorite."

"Uncle Jim said we needn't worry about meteorites on the moon, in spite of all the stories you read. The air isn't much, but it stops the grain-of-dust stuff, and we'd have seen the flash of one big enough to reach the ground. He might have had a fall, though; if it were bad enough it might have punctured his suit. We'd better start looking."

"Hadn't one of us better go up and report to Uncle Jim?" Bart was the more cautious of the two even in a situation like the present.

"If we do," replied Dart, "he's likely to order us to come up anyway until the station is back overhead. He'll say that either Pete's suit is all right or it isn't; if it is, he can wait, arid if it isn't we're too late already. He won't be worrying about us for a while, anyway; it would be better if we looked. Then if we find Pete, we can give a full report and he can stop worrying before he starts."

Bart was not too stupid to see the flaws in this argument, but he was willing to be persuaded and did not point them out.

"All right. I'll come over and park beside you, and we'll start looking. At least we know which mountain he was on. We'd better go out together; if there is something on that mountain which got Pete into trouble, we might be able to help each other better if one of us wasn't back baby-sitting over a radio."

"Right. I'll be outside waiting for you." Ten minutes later the two started up the slope.

Peter had been quite right in his estimate of the difficulties any searchers would face. While the sun was no lower than it had been half a day before, the shadows were at least as confusing as ever. Both boys carried lights, but even with these it was never possible to be sure from any great distance how deep a particular hole or crack might be. Bart was already tired, and could not make the speed that his brother could; after a few hours they had to return to the ships for food and rest.

The latter was brief, however, and before long they were back at the job. Neither was watching the earth as Peter had been, and the beginning of the eclipse took them by surprise.

"For gosh sake!" exclaimed Dart when the facts of the matter became apparent. "What are we going to do now? It's bad enough hunting through all these shadows, but if the sun's going out entirely we won't be able even to travel, let alone hunt."

"We just wait, I guess," replied Bart. "We'd better get back to the ships while we can, too."

"Why? Our suits have heaters good enough to keep us going, even if the temperature drops the way the books say it does during an eclipse."

"I'm not worried about the temperature—the rocks around us are way below zero now, except for the slopes that are getting full sunlight, but if Pete can drop out of sight with the sun shining and him concentrating on travel, we can do the same in the dark while we're concentrating on finding Pete. We'll be wasting our time and our batteries. We're not too far from the ships anyway, and this business will last only a couple of hours at the outside."

"All right." The two picked their way back to the ships, and each boarded his own—Dart thought briefly of going with his brother, but just as Peter had earlier he decided that he would feel better within reach of the Jabberwock's control panel. He seated himself before it, removed his helmet, and watched the outside landscape through the ports.

It was changing. The mountains had been standing out sharply against the star-sprinkled background, looking bright in spite of the dark rock which formed their bulks; now they seemed a little softer and dimmer. There was a suspicion of red in their color, rather like that on an afternoon on Earth when a person starts wondering whether he should still use color film or not. In the other direction, it was still impossible to look directly at the sun; but by squinting between close-pressed fingers Dart could see that it was well over half hidden by a great, dark, blurry circle. The eclipse had progressed some distance before the change in sunlight had caught the boys' notice.

Gradually the scenery grew darker, and tinged with a deeper red. The mountains became less prominent, and the stars peeping over their shoulders seemed to grow brighter as though they were taking charge of the scene previously monopolized by the sun. Earth and sun alike were cut in halves by the horizon, and gradually it became possible to look in that direction without shading the eyes.

Dart watched in fascination as the last brilliant orange sliver of the sun glowed through miles of the earth's air to reach his eyes. It looked like a burning coal set in a copper ring, for the half circle of the earth still above the horizon could now be seen in its entirety. Light was being filtered all around its rim through the halo of atmosphere, faintest at the left, brightening over the top and culminating at the right-hand edge in the flame of the nearly hidden sun.

Then the sun was gone, and only the ring remained. For a moment Dart was tempted to go up a little way so as Lo see the whole circle; he had even reached out a hand toward his main power switch when he was interrupted.

"Dart! What's that?"

"What's what?"

"Over there, on the mountain."

"I didn't see anything. I've been watching the eclipse."

"Then look. It must be three or four thousand feet up, but I'd swear it was a light—not very steady—appearing and fading—"

"I see it. Sort of Northern Lights thing."

"That's it. Do you suppose that's what it could be —Northern Lights?"

"I don't know. We're near the north pole, but I don't know whether that means anything on the moon." They fell silent for a moment, while ideas churned within both young brains. Bart was slightly the quicker of the two.

"That's a searchlight!"

"You're crazy. No one has a searchlight on the moon, and anyway you couldn't see the beam unless it was pointed right at you. Maybe that mountain was a volcano once, and it's starting to act up again. Maybe that's what got Pete."

"How could a volcano hurt him without our seeing it, or at least feeling the shock? They don't just open their mouths and snap people up like crocodiles."

"Maybe the gas—"

"Pete was wearing a space suit—remember?" Dart did not answer that one, and after a moment Bart went on, "Anyway, I'm going up and see. If it is a searchlight, I'll know."

"You're going to climb? You'll never make it in this light."

"No. I'll fly. I'll get up in line with it, and if it's a real light it'll get brighter—say, we're a couple of idiots; Pete had a flashlight."

"So what? We still couldn't see it like this, even if he had lugged his ship's landing lights up there."

"You may be right, but we're going to find out. You get a line on that thing; sight along anything in your ship that will serve—clamp a couple of pencils in place —do anything to get a sight on it, and if you move your ship afterward I'll skin you. I'm going up; I'll tell you what I see as soon as I know what it is."

Bart closed his power switches, nudged the main vernier up to a value just beyond the moon's acceleration of gravity, and drifted away from the surface, keeping his rocket upright with occasional brief shots from his side rockets. He hardly thought about what he was doing with the controls; he had handled his little ship enough by now so that such maneuvers required little more attention than walking. He was watching the flickering light, and hoping that it would not go out before he could get over it.

It was in the form of a beam, though its shape could not always be distinguished easily. The beam itself was steady in position, but flickered as though different parts of it were changing brightness from time to time. It lasted, however, and was distinct enough for him to judge its direction and bring the rocket into line with it. Fortunately, it was not shooting straight upward, so that when he moved into its path he could still see down at a sharp enough angle to spot its source. As he had expected, this looked like a dazzlingly bright star set in the mountainside, and almost without thinking he spoke into his transmitter.

"That you, Pete?"

"Sure is." The answer came instantly, in a voice just shaky enough to betray Peter's feelings. "Where are you?"

"About a mile above you. What happened—did you fall down a hole?"

"Jumped. I'll tell you later. Look, get my position as well as you can; I can't shine this thing much longer. I'm running out of oxygen."

"What? Are you burning a candle or something?"

"Tell you later. I'm going to shut off now. Get back on the ground; I'll give you five minutes, then I'll use the light again; you should be down and able to get a line by then. Get up here and pull us out as soon as you can."

Bart obeyed, and was actually on the ground before he realized fully what Peter had said. The significance of the "pull us out" struck him just as he touched ground; he gave such a yell that Dart was almost startled out of getting the sight he had been ordered to make.

"Dart! He must have Tumble with him! He's using some sort of light that won't last. Just get that bearing." "I have it."

"Good. I came down a mile or so from you; that should give us enough angle to pin-point the hole. We'll go up as soon as the eclipse is over."

Actually it was not quite as simple as that. There was no rope on any of the ships, and it was some time before enough wire could be collected from the repair lockers of the three rockets to reach the trapped boys.

Tumble was hauled out almost helpless; Peter used the wire as an assist in walking up the side of the hole. The three of them had no trouble in carrying the redhead back down the mountain, since a thirty-pound weight simply helped keep one's balance. Bart went into the Ion first, then Tumble was stuffed into the air lock from the outside by Peter and removed from the inside by Bart, and finally Peter entered his rocket. Dart was already on board his own, and as the door closed behind Peter he took off at two gravities to get out where he could make a report to Bowen at the station while the others took care of their rescue subject.

Tumble was hungry, dirty, tired, and generally uncomfortable; but he was quite evidently in no danger. He was, in fact, in much better shape than anyone confined in a space suit for five days had any right to be. Peter, once assured of this, turned to Bart.

"Say, I thought you were a friend of mine!" he said.

"So did I. What's biting you?"

"What on Earth—or what on the moon—took you so long to get up to us and pull us out? I wanted to see that eclipse; and now there won't be another for six months!"

FOUR RANGERS

TO THE watchers, the four rockets looked almost as though they were fastened together by invisible bars. They stayed side by side, each two hundred feet from its neighbor, while they swept over Niagara from the northern horizon. They nosed up together, and settled as one toward the plain of concrete from which the Polaris had lifted five weeks before. Their landing legs touched the ground within seconds of each other. The roar of their drive units ceased, and the onlookers saw the four cylinders clearly as the dust from the blast-pulverized concrete settled slowly.

Three of the ships had seen service; their metal hulls were frosted by the sandblasting effect of dust-grain meteors—even their windows were not as clear as they had once been. The fourth was mirror-bright, gleaming as though it had just been towed out to the ramp from the factory.

On board that new rocket, Tumble Tighe opened his switches and looked uneasily at his passenger. Hardly a word had been spoken during the short trip from the station, and the boy could read nothing from the expression on Bowen's face. In the ten days which had passed since the rescue on the moon, none of the boys had really talked to him; all were decidedly uneasy.

Tumble felt worst, of course, but Peter knew he himself had been pretty silly to step into a hole without stopping to see whether he could get out, and Bart and Dart could not yet think of any reasonable excuse for not at least calling the station to report why they were staying overtime. All four boys felt that they had pretty well cured Bowen of the idea that they would be good assistants in the exploring business, and none of them even had the comfort of feeling that it was all the fault of the other fellows.

Tumble was the youngest of the group by at least two years, and when even after what he felt was a very good landing he got no remarks from Bowen, his self-control suddenly gave way.

"Can't you say something? I know I'm a heel—I know I was a darned fool, and had no business taking a ship, and risking the lives of Pete and your nephews, and half-killing all the men in the station—I know it doesn't do any good to say I'm sorry—I know you can't trust me any more than I once trusted you; but at least say something, even if it's just to bawl me out! I thought when you let me fly you back to Earth, you might be going to say what you wanted, but you haven't said a thing all the way down. What are you going to do with me? And why don't you at least ease up on the other fellows? Everything they did was because of me, and you know it!"

Bowen looked up, but his expression didn't change. "I've been trying to decide what to say—to all of you—and how to say it. I think I know now.

"The ground crew is outside; help them get my chair down, please. Then tell the boys I want to see them, an hour from now, in the building where they had their ground school. I'll talk to all of you then. Just to give you something to think about in the meantime, Tumble: I didn't let you fly me down."

"But—but--that's silly—you came with me—"

"Help move the chair, please." Bowen's face did not soften, and he said no more.

The end of the hour found the four boys waiting impatiently in the little classroom where they had learned most of what they knew about Phoenix rockets. Uncle Jim was a few minutes late. Tumble had repeated Bowen's last words to the others, and they had spent most of the interval trying to decide what had been meant. The boys had not succeeded when the wheel chair rolled through the door.

Bowen faced the silent, scared group and looked thoughtfully at them for a moment.

"I gather," he said at length, "that all of you are pretty well ashamed of yourselves. So you should be. Three of you knew you were being tested for ability to solve one of the most important problems in the world today, and yet you did things which would make anyone who knew of them wonder what you used for common sense—the very last sort of mistakes you should have made. The fourth was in a different situation, since in spite of a lot of evidence he wasn't sure whether we were telling him the whole truth or were simply a group of swindlers and pirates. If he had stolen his rocket and tried to escape to Earth, I would have had nothing to say against his action. But when he went joy riding to the moon, it put him right in the same boat with the rest of you—or more accurately, in the same one you all stepped into later.

"There were really two parts to the idea which Peter had last spring. One involved the question of whether boys your age could overcome space sickness and learn to operate interplanetary rockets. That one was solved very satisfactorily—you can.

"The other one was the question of whether boys your age could be trusted to operate rockets, and explore the solar system without adult supervision—an important question, since it seems that such supervision can't be given. How do you think you did on that test?"

He was silent for a few moments, looking at each in turn.

"Dr. Bowen." Tumble spoke in a lower tone than any of them had heard him use.

"Yes, Tumble?"

"You're right in saying that I didn't trust you when I took the ship. I should have; I knew when I saw the station that you must be telling mostly the truth. Maybe it doesn't make any difference now, but I want to tell you how I've felt since, and why I felt the way I did.

"I never had any folks; one friend looked after me ever since I was too small to remember. He's been good to me. He's given me all I ever had, and it was he who told me all the things I believed when you first caught me. I couldn't believe he was lying to me.

"I know now that he was either lying, or honestly wrong. I believe the second, because of what he's done for me, but I'll never be able to tell you how I felt when I got back to the station and saw the shape you and the other men were in, and knew it was because of me that you'd done what you did. You had no reason to do anything for me at all, but all of you did. That was enough for me. You were as much friends of mine as —he is.

"I'm not going to tell you who the person is who had me spying on you, because I still can't believe he meant to do anything really wrong; but I'm done working for him against you. You can kick me out or let me stay—that doesn't matter; I won't tell anything you don't want me to, either way."

Bowen's features softened a trifle, and something that might have been the beginning of a smile appeared on his face.

"Good enough, Tumble. How about the rest of you?" Bart answered for the three.

"What can we say? We can see how silly we were when we look at it now, but it all seemed the right thing to do then. I don't know whether we'd be any different next time, either. Pete saw Tumble and started to get to him without thinking; Dart and I missed Pete, and couldn't see leaving him."

"And if any one of you had done differently, I'd have disowned him!" The smile was in full evidence now. "Don't misunderstand me; you were a silly bunch of youngsters, and don't think for one moment you did right. Just the same, you showed the courage and willingness to help others even at the risk of your own hides which any explorer has to have, and that's what will probably keep you alive in this business. You're a bunch of silly, insubordinate, unthinking, and impulsive young idiots, and I'll probably have to invent some drastic forms of punishment to keep you in hand for the next few years; but if you are willing to risk it, I certainly am. Are you on?"

"We are!" The three voices rang out together; only Tumble was silent. Bowen looked at him.

"What's the matter, young fellow? Standing out? Didn't you understand what I said to you in the rocket just after we landed?"

"No, sir."

"I didn't let you fly me down—I ordered you to. These nephews of mine and their intellectual friend are all reasonably good pilots, but I wouldn't trust one of them to fly me from the station to Earth without varying more than two percent from a one "G" acceleration the whole way. You did it, and I knew from your instructors that you'd do it. Now, are you a pilot with the others, or do you have some silly idea that we don't want you?"

"I'm with you, sir!"

"Uncle Jim, to you. You have some folks now, whether you know it or not. I can always use another nephew; I may want to get rid of some of the present ones.

"Now," he went on before Tumble had any chance to reply, "are the lot of you ready for work, or are you some of those characters who think the best way to start a job is with a vacation?"

"Where do we go?" There were four voices this time.

"Mars?" added Tumble hopefully.

"You'll get to Mars in good time; just be patient. Right now there are more important things than finding out if the canals are ditches or not. There are people who want to know what's going on in the sun—"

"What?"

"—and since we can't very well go there, they want instruments set up in the next best place. Pete, as the walking encyclopedia of the Space Rangers, tell your friends about the planet Mercury."

But even Peter did not know about the Tunnel of Fire. That came later, and by then they all knew it as well as he did.