"Nothing brilliant," said Jim. "We could use super-output voice amplifiers and yell halfway across the planet if we didn"t have radio. We can radio far better than this c.o.c.keyed system of signaling."

"We might cut the power."

"Or spread out quite a bit. I still say, however, that this is no signaling system."

"It works like one."

"So can a clothesline be made to serve as a transmitter of intelligence. But it"s prime function is completely different."

"S"pose we have a super-clothesline here?" asked Christine.

"The way that hammer felt last night, I"m not too sure that this might not be some sort of tractor beam,"

said Jim.

"Tractor beams are mathematically impossible."

"Yeah, and they proved conclusively that a bird cannot fly," said Jim. "That was before they found the right kind of math. Up until Clerk Maxwell"s time, radio was mathematically impossible. Then he discovered the electromagnetic equations, and we"re squirting signals across the Inner System every day.

And when math and fact do not agree, which changes?"

"The math. Galileo proved that. Aristotle said that a heavy stone will fall faster. Then Galileo changed the math of that by heaving a couple of boulders off the Leaning Tower. But what have we here?"

"Has anyone toyed with the transmission of power?"

"Sure. A lot of science-fiction writers have their imaginary planets crisscrossed with transmitted power.

Some broadcast it, some have it beamed to the consumer. When they use planes, they have the beamcoupled to an object-finder so as to control the direction of the beam. I prefer the broadcasting, myself.

It uncomplicates the structure of the tale."

"I mean actually?"

"Oh, yes. But the losses are terrific. Useful power transmission is a minute percentage of the total output of the gadget. Absolutely impractical, especially when copper and silver are so plentiful to string along the scenery on steel towers. No good."

"But look at this c.o.c.keyed thing. Christine puts in a couple of hundred amps; I take them off my end.

Believe it or not, the output meter at my end was getting a lot more soup than I was pouring in."

"And my gadget was not taking anything to speak of," said Barney.

"Supposing it was a means of transmitting power. How on Mars did they use a single tower there in the middle of the Red Desert? We know there was a Martian city at Ca.n.a.lopsis, and another one not many miles from Lincoln Head. Scribbled on the outer cover of this book is the legend: "Tower Station, Red Desert," and though the Martians didn"t call this the "Red Desert," the terminology will suffice for nomenclature."

"Well?" asked Jim.

"You notice they did not say: "Station No. i," or "3" or "7." That means to me that there was but one."

"Holy Smoke! Fifteen hundred miles with only one station? On Mars the curvature of ground would put such a station below the electrical horizon-" Jim thought that one over for a minute and then said: "Don"t tell me they bent the beam?"

"Either they did that or they heated up the sand between," said Barney cryptically. "It doesn"t mind going through nonconducting walls, but a nice, fat ground... blooey, or I miss my guess. That"d be like grounding a high line."

"You"re saying that they did bend- Whoosh, again!"

"What was that alignment problem? Didn"t we align the deflecting anodes somehow?"

"Yeah, but you can"t bend the output of a cathode ray tube externally of the deflection plates."

"But this is not electron-beam stuff," objected Barney. "This is as far ahead of cathode-ray tubes as they are ahead of the Indian signal drum or the guy who used to run for twenty-four miles from Ghent to Aix."

"That one was from Athens to Sparta," explained Christine, "the Ghent to Aix journey was a-horseback, and some thousand-odd years after."

"Simile"s still good," said Barney. "There"s still a lot about this I do not understand."

"A masterpiece of understatement, if I ever heard one," laughed Jim. "Well, let"s work on it from that angle. Come on, gang, to horse!"

"Now," said Altas, "you will find that the best possible efficiency is obtained when the currents in these two resistances are equal and opposite in direction. That floats the whole tube on the system, and makes it possible to run the tube without any external power source. It requires a starter-source for aligning and for standby service, and for the initial surge; then it is self-sustaining. Also the in-phase voltage can not better be obtained than by exciting the phasing anode with some of the main-line power. That mustalways be correctly phased. We now need the frequency generator no longer, and by increasing the power rheostat to full, the tube will take up the load. Watch the meters, and when they read full power, you may throw the cut-over switch and make the tube self-sustaining. Our tower will then be in perfect service, and you and I may return to our home below."

Than performed the operations, and then they left, taking the old tube with them.

And on Terra, Sargon of Akkad watched ten thousand slaves carry stone for one of his public buildings.

He did not know that on one of the stars placed in the black bowl of the evening sky for his personal benefit, men were flinging more power through the air than the total output of all of his slaves combined.

Had he been told, he would have had the teller beheaded for lying because Sargon of Akkad couldn"t possibly have understood it- "You know, we"re missing a bet," said Jim. "This in-phase business here. Why shouldn"t we hang a bit of the old wall-socket juice in here?"

"That might be the trick," said Barney.

Jim made the connections, and they watched the meters read up and up and up-and from the street below them a rumbling was heard. Smoke issued from a creva.s.se in the pavement, and then with a roar, the street erupted and a furrow three feet wide and all the way across the street from Jim Baler"s residence to Barney Carroll"s garage lifted out of the ground. It blew straight up and fell back, and from the bottom of the furrow the smoldering of burned and tortured wiring cast a foul smell.

"Wham!" said Barney, looking at the smoking trench. "What was that?"

"I think we"ll find that it was the closest connection between our places made by the Electric Co.," said Jim.

"But what have we done?"

"I enumerate," said Christine, counting off on her fingers. "We"ve blasted in the facade of the City Hall.

We"ve caused a couple of emergency flier-landings within the city limits. We"ve blown fuses and circuit breakers all the way from here to the main powerhouse downtown. We"ve stalled a few dozen automobiles. We"ve torn or burned or cut the end off of one hammer and have fractured the wall with it... where did that go, anyway, the hammerhead? We"ve burned wallpaper. We"ve run our electric bill up to about three hundred dollars, I"ll bet. We"ve bunged up a dozen meters. And ,now we"ve ripped up a trench in the middle of the street."

"Somewhere in this set-up, there is a return circuit," said Jim thoughtfully. "We"ve been taking power out of the line, and I"ve been oblivious of the fact that a couple of hundred amperes is too high to get out of our power line without trouble. What we"ve been doing is taking enough soup out of the public utility lines to supply the losses only. The power we"ve been seeing on our meters is the build-up, recirculated!"

"Huh?"

"Sure. Say we bring an amp in from the outside and shoot it across the street. It goes to the wires and comes back because of some electrical urge in our gadgets here, and then goes across the street inphase with the original. That makes two" amps total crossing our beam. The two come back and we have two plus two. Four come back, and we double again and again until the capability of our device is at saturation. All we have to do is to find the ground-return and hang a load in there. We find the transmitter-load input, and supply that with a generator. Brother, we can beam power all the way from here to Ca.n.a.lopsis on one relay tower!"Barney looked at his friend. "Could be."

"Darned right. What other item can you think of that fits this tower any better? We"ve run down a dozen ideas, but this works. We may be arrested for wrecking Lincoln Head, but we"ll get out as soon as this dingbat hits the market. Brother, what a find!"

"Fellows, I think you can make your announcement now," smiled Christine. "They won"t burn you at the stake if you can bring electric power on a beam of pure nothing. This time you"ve hit the jackpot!"

It is six thousand Terran Years since Sargon of Akkad held court that was lighted by torch. It is six thousand years, Terran, since Than and Altas replaced the link in a power system that tied their cities together.

It is six thousand years since the beam tower fell into the Red Desert and the mighty system of beamed power became lost as an art. But once again the towers dot the plains, not only of Mars, but of Venus and Terra, too.

And though they are of a language understood by the peoples of three worlds, the manuals of instruction would be as cryptic to Than as his manual was to Barney Carroll and Jim Baler.

People will never learn.

THE OTHER SIDE OF THE SKY.

by Arthur C. Clarke

SPECIAL DELIVERY.

I CAN STILL REMEMBER the excitement, back in 1957, when Russia launched the first artificial satellites and managed to hang a few pounds of instruments up here above the atmosphere. Of course, I was only a kid at the time, but I went out in the evening like everyone else, trying to spot those little magnesium spheres as they zipped through the twilight sky hundreds of miles above my head. It"s strange to think that some of them are still there-but that now they"re below me, and I"d have to look down toward Earth if I wanted to see them...

Yes, a lot has happened in the last forty years, and sometimes I"m afraid that you people down on Earth take the s.p.a.ce stations for granted, forgetting the skill and science and courage that went to make them.

How often do you stop to think that all your long-distance phone calls, and most of your TV programs, are routed through one or the other of the satellites? And how often do you give any credit to the meteorologists up here for the fact that weather forecasts are no longer the joke they were to our grandfathers, but are dead accurate ninety-nine per cent of the time?

It was a rugged kfe, back in the seventies, when I went up to work on the outer stations. They were being rushed into operation to open up the millions of new TV and radio circuits which would be available as soon as we had transmitters out in s.p.a.ce that could beam programs to anywhere on the globe.

The first artificial satellites had been very close to Earth, but the three stations forming the great triangle of the Relay Chain had to be twenty-two thousand miles up, s.p.a.ced equally around the equator. At this alt.i.tude- and at no other-^-they would take exactly a day to go around their orbit, and so would stay poised forever over the same spot on the turning Earth.

In my time I"ve worked on all three of the stations, but my first tour ofCopyright 1957 by Royal Publications, Inc.

Copyright 1958 by Arthur C. Clarke.

Reprinted by permission of the author and the author"s agents, Scott Meredith Literary Agency, Inc.

duty was aboard Relay Two. That"s almost exactly over Entebbe, Uganda, and provides service for Europe, Africa, and most of Asia. Today it"s a huge structure hundreds of yards across, beaming thousands of simultaneous programs down to the hemisphere beneath it as it carries the radio traffic of half the world. But when I saw it for the first time from the port of the ferry rocket that carried me up to orbit, it looked like a junk pile adrift in s.p.a.ce. Prefabricated parts were floating around in hopeless confusion, and it seemed impossible that any order could ever emerge from this chaos.

Accommodation for the technical staff and a.s.sembling crews was primitive, consisting of a few unserviceable ferry rockets that had been stripped of everything except air purifiers. "The Hulks," we christened them; each man had just enough room for himself and a couple of cubic feet of personal belongings. There was a fine irony in the fact that we were living in the midst of infinite s.p.a.ce-and hadn"t room to swing a cat.

It was a great day when we heard that the first pressurized living quarters were on their way up to us--complete with needle-jet shower baths that would operate even here, where water-like everything else-had no weight. Unless you"ve lived aboard an overcrowded s.p.a.ceship, you won"t appreciate what that meant. We could throw away our damp sponges and feel really clean at last...

Nor were the showers the only luxury promised us. On the way up from Earth was an inflatable lounge s.p.a.cious enough to hold no fewer than eight people, a microfilm library, a magnetic billiard table, lightweight chess sets, and similar novelties for bored s.p.a.cemen. The very thought of all these comforts made our cramped life in the Hulks seem quite unendurable, even though we were being paid about a thousand dollars a week to endure it.

Starting from the Second Refueling Zone, two thousand miles above Earth, the eagerly awaited ferry rocket would take about six hours to climb up to us with its precious cargo. I was off duty at the time, and stationed myself at the telescope where I"d spent most of my scanty leisure. It was impossible to grow tired of exploring the great world hanging there in s.p.a.ce beside us; with the highest power of the telescope, one seemed to be only a few miles above the surface. When there were no clouds and the seeing was good, objects the size of a small house were easily visible. I had never been to Africa, but I grew to know it well while I was off duty in Station Two. You may not believe this, but I"ve often spotted elephants moving across the plains, and the immense herds of zebras and antelopes were easy to see as they flowed back and forth like living tides on the great reservations.

But my favorite spectacle was the dawn coming up over the mountains in the heart of the continent. The line of sunlight would come sweeping across the Indian Ocean, and the new day would extinguish the tiny, twinkling galaxies of the cities shining in the darkness below me. Long before the sun had reached the lowlands around them, the peaks of Kilimanjaro and Mount Kenya would be blazing in the dawn, brilliant stars still surrounded by the night. As the sun rose higher, the day would march swiftly down their slopes and the valleys would fill with light. Earth would then be at its first quarter, waxing toward full.

Twelve hours later, I would see the reverse process as the same mountains caught the last rays of the setting sun. They would blaze for a little while in the narrow belt of twilight; then Earth would spin into darkness, and night would fall upon Africa.It was not the beauty of the terrestrial globe I was concerned with now. Indeed, I was not even looking at Earth, but at the fierce blue-white star high above the western edge of the planet"s disk. The automatic freighter was eclipsed in Earth"s shadow; what I was seeing was the incandescent flare of its rockets as they drove it up on its twenty-thousand-mile climb.

I had watched ships ascending to us so often that I knew every stage of their maneuver by heart. So when the rockets didn"t wink out, but continued to burn steadily, I knew within seconds that something was wrong. In sick, helpless fury I watched all our longed-for comforts-and, worse still, our mail!-moving faster and faster along the unintended orbit. The freighter"s autopilot had jammed; had there been a human pilot aboard, he could have overridden the controls and cut the motor, but now all the fuel that should have driven the ferry on its two-way trip was being burned in one continuous blast of power.

By the time the fuel tanks had emptied, and that distant star had flickered and died in the field of my telescope, the tracking stations had confirmed what I already knew. The freighter was moving far too fast for Earth"s gravity to recapture it-indeed, it was heading into the cosmic wilderness beyond Pluto...

It took a long time for morale to recover, and it only made matters worse when someone in the computing section worked out the future history of our errant freighter. You see, nothing is ever really lost in s.p.a.ce. Once you"ve calculated its...o...b..t, you know where it is until the end of eternity. As we watched our lounge, our library, our games, our mail receding to the far horizons of the solar system, we knew that it would all come back one day, in perfect condition. If we have a ship standing by it will be easy to intercept it the second time it comes around the sun-quite early in the spring of the year A.D. 15,862.

FEATHERED FRIEND.

To THE BEST OF MY KNOWLEDGE, there"s never been a regulation that forbids one to keep pets in a s.p.a.ce station. No one ever thought it was necessary-and even had such a rule existed, I am quite certain that Sven Olsen would have ignored it.

With a name like that, you will picture Sven at once as a six-foot-six Nordic giant, built like a bull and with a voice to match. Had this been so, his chances of getting a job in s.p.a.ce would have been very slim; actually he was a wiry little fellow, like most of the early s.p.a.cers, and managed to qualify easily for the i jo-pound bonus that kept so many of us on a reducing diet.

Sven was one of our best construction men, and excelled at the tricky and specialized work of collecting a.s.sorted girders as they floated around in free fall, making them do the slow-motion, three-dimensional ballet that would get them into their right positions, and fusing the pieces together when they were precisely dovetailed into the intended pattern. I never tired of watching him and his gang as the station grew under their hands like a giant jigsaw puzzle; it was a skilled and difficult job, for a s.p.a.ce suit is not the most convenient of garbs in which to work. However, Sven"s team had one great advantage over the construction gangs you see putting up skysc.r.a.pers down on Earth. They could step back and admire their handiwork without being abruptly parted from it by gravity...

Don"t ask me why Sven wanted a pet, or why he chose the one he did. I"m not a psychologist, but I must admit that his selection was very sensible. Claribel weighed practically nothing, her food requirements were infinitesimal-and she was not worried, as most animals would have been, by the absence of gravity.

I first became aware that Claribel was aboard when I was sitting in the little cubbyhole laughingly called my office, checking through my lists of technical stores to decide what items we"d be running out of next.

When I heard the musical whistle beside my ear, I a.s.sumed that it had come over the station intercom,and waited for an announcement to follow. It didn"t; instead, there was a long and involved pattern of melody that made me look up with such a start that I forgot all about the angle beam just behind my head. When the stars had ceased to explode before my eyes, I had rny first view of Claribel.

She was a small yellow canary, hanging in the air as motionless as a hummingbird-and with much less effort, for her wings were quietly folded along her sides. We stared at each other for a minute; then, before I had quite recovered my wits, she did a curious kind of backward loop I"m sure no earthbound canary had ever managed, and departed with a few leisurely flicks. It was quite obvious that she"d already learned how to operate in the absence of gravity, and did not believe in doing unnecessary work.

Sven didn"t confess to her ownership for several days, and by that time it no longer mattered, because Claribel was a general pet. He had smuggled her up on the last ferry from Earth, when he came back from leave-partly, he claimed, out of sheer scientific curiosity. He wanted to see just how a bird would operate when it had no weight but could still use its wings.

Claribel thrived and grew fat. On the whole, we had little trouble concealing our unauthorized guest when VIP"s from Earth came visiting. A s.p.a.ce station has more hiding places than you can count; the only problem was that Claribel got rather noisy when she was upset, and we sometimes had to think fast to explain the curious peeps and whistles that came from ventilating shafts and storage bulkheads. There were a couple of narrow escapes--but then who would dream of looking for a canary in a s.p.a.ce station?

We were now on twelve-hour watches, which was not as bad as it sounds, since you need little sleep in s.p.a.ce. Though of course there is no "day" and "night" when you are floating in permanent sunlight, it was still convenient to stick to the terms. Certainly when I woke up that "morning" it felt like 6:00 A.M. on Earth. I had a nagging headache, and vague memories of fitful, disturbed dreams. It took me ages to undo my bunk straps, and I was still only half awake when I joined the remainder of the duty crew in the mess. Breakfast was unusually quiet, and there was one seat vacant.

"Where"s Sven?" I asked, not very much caring.

"He"s looking for Claribel," someone answered. "Says he can"t find her anywhere. She usually wakes him up."

Before I could retort that she usually woke me up, too, Sven came in through the doorway, and we could see at once that something was wrong. He slowly opened his hand, and there lay a tiny bundle of yellow feathers, with two clenched claws sticking pathetically up into the air.

"What happened?" we asked, all equally distressed.

"I don"t know," said Sven mournfully. "I just found her like this."

"Let"s have a look at her," said Jock Duncan, our cook-doctor-diet.i.tian. We all waited in hushed silence while he held Claribel against his ear in an attempt to detect any heartbeat.

Presently he shook his head. "I can"t hear anything, but that doesn"t prove she"s dead. I"ve never listened to a canary"s heart," he added rather apologetically.

"Give her a shot of oxygen," suggested somebody, pointing to the green-banded emergency cylinder in its recess beside the door. Everyone agreed that this was an excellent idea, and Claribel was tucked snugly into a face mask that was large enough to serve as a complete oxygen tent for her.

To our delighted surprise, she revived at once. Beaming broadly, Sven removed the mask, and shehopped onto his finger. She gave her series of "Come to the cookhouse, boys" trills-then promptly keeled over again.

"I don"t get it," lamented Sven. "What"s wrong with her? She"s never done this before."

For the last few minutes, something had been tugging at my memory. My mind seemed to be very sluggish that morning, as if I was still unable to cast off the burden of sleep. I felt that I could do with some of that oxygen-but before I could reach the mask, understanding exploded in my brain. I whirled on the duty engineer and said urgently: "Jim! There"s something wrong with the air! That"s why Claribel"s pa.s.sed out. I"ve just remembered that miners used to carry canaries down to warn them of gas."