Solarite
Arcot, Morey and Wade 01.2
Amazing Stories – November 1930
(1930)*
John W. Campbell, Jr.
illustrated by MOREY

	THE lights of the great Transcontinental Airport were blazing in cheering splendor. Out there in the center of the broad field a dozen men were silhouetted in the white brilliance, looking up at the sky, where the stars winked cold and clear on the jet background of the frosty night. A slim crescent of the moon showed in the west, a thin sickle of light that in no way dimmed the cold flame of the brilliant stars.

	There seemed one now that moved across the motionless field of far-off suns, one that shot toward the airport in a long, swift curve. The men on the broad plane murmured and pointed up at it as it swept low over the blazing lights of New York. Lower it was now, the towering city behind it. Half a mile into the air the buildings rose in shining glory of colored tile that shone brightly in the sweeping play of ever-changing colored floodlights, while above, like long fingers of crimson and green and gold, every color of the rainbow—the long beams of the spotlights reached out into the night.

	One of them picked out the descending machine, and it suddenly leaped out of the darkness as a shining, stream-fined cylinder, a cylinder with a great halo of blue fire, as the beam of the spotlight set it off from the jet black night.

	In an instant the ship was vast before the eyes of the waiting men, and it had landed gently on the field, was rolling smoothly, gracefully toward them.

	Two dozen men climbed from the great ship, shivering in the icy blast that swept across the field, spoke a moment with the men on the field, then climbed quickly into the grateful warmth of the waiting field car. In a moment they were moving rapidly toward the lights of the field house, half a mile off.

	Behind them a huge ship leapt straight into the air, then suddenly pointed its nose up at an angle of thirty degrees and shot high into the air at an unbelievable speed. In an instant it was gone. At the field house the party was breaking up rapidly.

	"We want to thank you, President Morey, for your demonstration of the new ship tonight. I am sure we all appreciate the kindness you have shown the press, and you, Dr. Arcot, for answering our many Questions about the new ship." The reporters were filing out quickly now, anxious to get the news into the morning editions, for it was after one o'clock now. Each was taking a small slip of paper from the attendant standing at the exit, the official statement of the company. At last all had left but the six men who were responsible for tins wonderful new machine.

	This night had witnessed the official demonstration of the first of the Arcot-Morey molecular motion ships. Small as this ship was, compared to the titanic ships that were to come, yet it had a passenger capacity of over three thousand, as great as that of any of the existing winged planes, and its speed was terrifically greater. The trip from the west coast to the eastern had been made in less than one hour. At a speed close to one mile a second the great ship had shot through the thin air, twenty-five miles above the dark earth. Propelled and sustained by the energy of heat, it needed no wings and could attain terrific speed. In all matter the molecules are in rapid motion, the motion being responsible for their temperature, but this motion is ordinarily in every direction, the uncountable billions of molecules each moving in a different direction, the law of averages balances out their individual motions, and they make no progress. Just four months ago Arcot, Junior, working with Morey, Junior, had discovered that very high frequency electrical vibrations could be made to affect these molecules and make them all move in the same direction. If all the molecules of a piece of matter move in the same direction, obviously the entire body is moving in that direction.

	In this car a huge bar of metal was so affected, and its molecules all tried to move forward, but the mass of the car held it back, and the molecules were slowed down. Slow-moving molecules mean a low temperature, and at once these molecules absorbed heat from the molecules of the surrounding air, and swiftly the great car was accelerated. Similar devices steered the great ship and another series of such power units directed upward held it motionless vertically, or made it rise or sink.

	No matter what the speed of the ship, the molecules were always trying to go faster, for who can say how fast the molecules of the earth's atmosphere are moving? They have their individual motions; in addition the earth spins on its axis, the entire planet revolves about the sun, while the whole system moves on through space at ten miles a second. Thus there was no limit but the speed of light to the velocity that the car could attain.

	This invention had been turned over to the Transcontinental Air lines, whose president was the father of Morey, Junior, the co-inventor of the new apparatus.

-

	ARCOT was a theoretical physicist but Morey was a mathematician, and it was with his aid that Arcot was able to get the mathematical equation of his ideas. Arcot seemed always to be able to sense the solution to the problem with a brilliant leap of genius, the general answer, but it was Morey's careful mathematical proof, following and amplifying the ideas Arcot outlined, that led to their successful operation.

	"Arcot," said Morey, Senior, after the pressmen had left the room, "as President of this company I certainly want to thank you for the tremendous thing you have given us to use. As your friend and as a citizen, I want to thank you for the wonderful weapon. War is impossible.

	"You have 'sold' us this machine—but how can we repay you? Before this, time and time again, you have sold us your different machines, the ideas that have made it possible for our line to attain its present high position in the world transportation network. All you have ever accepted is the laboratory you use, its upkeep, and a small amount annually. What can we do to show our appreciation this time?"

	"Why," answered Arcot smiling broadly, "you have not stated the terms correctly. Legally I have the laboratory in which to work, which your Company maintains, and whatever amount of personal income I wish to draw. There isn't even a 'within reason' clause in it. As a matter of fact, it should read that I have a fully equipped lab to putter around in, all the time I want to amuse myself, all the money I want—and the laboratory to amuse myself in. What more could I want?"

	"I suppose that is all true—but when you draw only about six thousand a year for personal expenses—why a good clerk could get that—and you, admittedly the most brilliant physicist of the earth, are satisfied! I don't feel that we are paying you properly!"

	"But the clerk might have a family—I haven't—how could I use the money if I did draw more? But you can repay me this time," added Arcot more seriously, "for this latest thing has made a new thing possible. I have always wanted to be able to visit other planets—it has been the dream of many a scientist for the last three centuries. This machine has made it possible. If you are willing—we could start by the spring of 2117. We have all been busy working on that ship; finally the first of the molecular ships is finished. I want to start work on the first interplanetary ship. For this I will need to have Fuller's help. Now that he has finished his work in designing that ship—I think he will be willing to help on my problem—he said so this evening. The proposition will be expensive, of course, and that is where I must ask you to help me. I think, however, that it may be a paying proposition, at that, for there will no doubt be many new sources of materials on the other planets."

	They had walked out to the shed where Arcot's private molecular motion car stood, the first machine that the world had ever seen, that used the heat of the sun to drive it and maintain it Thoughtfully the president of the great Transcontinental Lines looked up at it. Small it was compared with the great machine that had just brought them east, but of the same swift type. It was a thing of graceful beauty here even as it rested on the ground, its long curving streamlines giving it wonderful grace. The men stood in thoughtful silence for a minute—the young men eager to hear the verdict of their prospective backer.

	"If it were the money you asked for, Arcot, I would gladly give you double the sum, but there is only one thing that worries me. I know perfectly well that if you do go, my son will go with you, and Fuller and Wade will naturally go too. Each of you has come to mean a lot to me. You and Fuller have known my son since college days. I have known Wade but three months, but every day I grow to like him more. There is no denying the fact that any such trip is a terrifically dangerous proposition. But if you were lost, there would be more than my personal loss. We would lose some of the most brilliant men on earth. You, for instance, are conceded as being the world's most brilliant physicist; Fuller is one of the greatest designing engineers; Wade is rapidly rising into prominence as a chemist and as a physicist; and my son is certainly a good mathematician.

	"But you men should know how to get out of scrapes just that much better. Certainly there are few men on earth who would not be willing to back such a group of men—or any one of you, for that matter! I will back your trip! But although I know that Arcot and my son can handle a gun fairly well, I don't know so much about Wade and Fuller. What experience have you two had?"

	"I think my greatest recommendation will be as cook on the trip, Mr. Morey. I have done the cooking on a number of camping trips and I think that food has a considerable effect on the success of an expedition. I can shoot a bit, too," said Fuller.

	"I come from the west, and have had a good bit of fun in the Rockies; there are still some mountain lions and some deer there. I also have a speaking acquaintance with the new gun, which Arcot developed in connection with his molecular motion. But there is so little you know about me—and most of it bad—I don't see how I really get in on this opportunity—but I certainly don't intend to keep the old boy knocking—I am with you, since I am invited!"

	Wade had been known as the Pirate—and it was through Arcot's efforts that he had finally been cured. It was found that he had been suffering from kleptomaniacy induced by a blood clot in the brain, and after a simple operation, performed by one of the leading surgeons of the country, he had been restored to normal, as one of the world's foremost scientists. He had at once been invited to join Arcot in his lab, to keep, as Arcot explained, all possible competition in the family! Since then Wade had proved himself well worthy of his position.

	"You're invited all right, Wade—on one condition—that you just forget all about what happened under the influence of the blood-clot.

	"Then you will definitely support us?" Arcot was jubilant.

	"Yes, I think I will," replied Morey, Senior, seriously, "for I think it is worth doing. There may be great advantages coming from the trip."

	The tremendous advantages that actually did come from the trip, Mr. Morey could not, of course, foresee, but we certainly must be thankful that he did decide to back this trip.

	"I want to thank you for that, Mr. Morey—wait till Dad gets back from that European conference—he can help us too!" Arcot had evidently been making his plans for the trip!

-

	THE young men climbed into the ship, to start for their apartment. Arcot was piloting, and out into the cold night air the ship rode easily, then up, up, up—up through the dull atmosphere, till they hung fifty miles up, on the outer verge of the airy blanket. Here in space they looked out in silent thought at the magnificent blazing stars of space. Here, where the dust-laden air could no longer mask their true colors, the stars shone unwinkingly, steadily, and in a glory that no man has ever seen, save thus far out in space. No longer were they all the same scintillating blue, all alike, as we see them from earth, but here they shone in a wonderous riot of color, as varied and as beautiful as the display of colored floodlights in some great city. They were tiny pinpoints of brilliant color, they were red, and green, and orange; there were yellow ones and deep blue ones—they shone in intense brightness, and each was tiny beyond comprehension; here, with no atmosphere to diffuse their brilliance, each was tiny to the vanishing point, mere points of light on a soft black that has no equal, the utter black of space, where there is nothing visible. Here no air blurred the stars to great pointed splotches.

	Then slowly Arcot let the machine settle to the blazing city miles below.

	"I love to go out there and look at those cold, pinpoint lights; they seem to draw me out there to investigate—the lure of other worlds. There always has come a sense of unfulfilled longing—the desire to go—and never before have I been able to hope to. Now—I will be out there by next spring!" Arcot paused and looked up at the mighty field of stars that arched over his head to be lost on either horizon. It was a wonderful night!

	"Where shall we go first, Dick?" asked Wade softly as he gazed out at the far-off suns of space. One wanted to talk softly here—there was a mighty grandeur about it that lured, yet oppressed one.

	"I have thought of that for the last four months. I have looked up statistics, and now that it is decided that we will start, we must decide where we are to go.

	"Of course we cannot leave the solar system. There are not many places we can go, let us eliminate them one by one, beginning with the sun and working out.

	"Obviously we will not go to the sun. Mercury circles the sun at a distance of 36,000,000 miles. It is the smallest of the major planets—only slightly larger than the moon, and very like it in many ways. It is easy to eliminate that—for it revolves always with the same face to the sun. The tremendous tidal action of the sun has through the ages, slowed Mercury's axial the sun, and once in those eighty-eight days it turns on rotation till it merely keeps the same face toward the sun. Once every eighty-eight days it revolves about its axis. Thus always it faces the sun on one side and space with the other. One side is as hot and bleak as a lava bed, the other as cold as far off Neptune.

	"Again it is too small to maintain an atmosphere. It has neither air nor water. Were we to visit it we would find no life, and could not leave the ship.

	"This also applies to the moon, so thus we eliminate two possibilities and into the bargain I might say that the moon is so readily investigated telescopically that it scarcely repays investigation in this way.

	"Next out from the sun is Venus—the beautiful planet. Venus gets twice the radiation from the sun that our earth does, and she is nearly the same size, her diameter is 7,700 miles while that of the earth is 7,900. The entire planet is coated with a perpetual layer of heavy clouds, that has never broken but once since men have observed it. These clouds mean that it will reflect a tremendous amount of light, and so it does. In fact so brilliant is the planet from our earth that it can be seen at midday, when in the right position, and on moonless nights, will cast a shadow.

	"The mass is about 82 per cent, that of the earth, so that the gravitational force will be about 85 per cent, due to the lesser radius. Thus Wade, who weighs almost exactly 200, will weigh about 170 there.

	"The very clouds that hide the surface from us, show that the planet has a deep atmosphere. Measurements, made of the amount of heat radiated from the night side of the planet as long ago as 1928 showed that the amount of heat radiated required that the planet have a fairly short day. The absence of markings in the smooth layer of clouds makes it impossible to know the length of the day. The only time there was any break in the clouds was about four centuries ago, when two men observed the break, which lasted several days, and each got a result for the length of the day, but the results were rather surprising! One was twenty-three hours, and the other twenty-four days. They can, however, be reconciled. If the one man observed the break in the clouds once each night that it lasted, at the same hour, he would see that, in twenty-four hours, the twenty-three-hour planet would have made one turn, and a bit more. In twenty-four days he would have found that it was again as it was the first night, for the planet would have gained one revolution on the earth. There are obviously two possible interpretations.

	"Venus is the planet of mystery—most like the earth, it is ever shrouded in clouds.

	"It is but 67,000,000 miles from the sun, and we are particularly fortunate, in that next spring it will be in conjunction with the earth, and we will be but about thirty-five million miles from it.

	"As you see I rather favor Venus—it is a mystery, and we could leave the car to explore that planet.

	"Mars is next to be considered. It is now at superior conjunction, or about two hundred and thirty million miles off. I think that eliminates it for the present, and into the bargain, no human being could live on that planet by any stretch of the imagination. In daytime he would almost fry, and at night freeze solid. That life might develop there is certainly conceivable, but we would not be able to explore it. It is also too small to have a very dense atmosphere.

	"Jupiter, the giant of the Solar system is next. Did you know that at one time, people on a planet circling one of the nearer stars would have said the sun was a double star? When Jupiter was first thrown off from the sun it was a mighty glowing sea of fire, of about one one-hundredth the brilliance of the sun. This would certainly be recorded as a double star. Jupiter, whose mass is about one one-thousandth that of the sun, is big enough to swing it a bit. The center of gravity of the solar system is not in the center of the sun, but leans toward Jupiter quite appreciably.

	"Jupiter has so great a mass that the gravity would be fatal, but the quick rotation so reduces it, by centrifugal force, that a man might be able to stand it. Though. Jupiter measures a quarter of a million miles around at the Equator, it spins on its axis once every ten hours—or really a bit less.

	"Jupiter is certainly very interesting in itself, but there are even more interesting things about it, for it is, as I said, a sort of a second, smaller sun in the solar system, a cold sun now it is true, but still a sun. Like the greater sun, it has a system of planets, more or less extensive. Some, indeed, are larger than some of the planets of the sun. Both Mercury and Mars are smaller than Ganymede, the largest of Jupiter's satellites. This might be well worth exploring, but it too has such a small size that there is no great atmosphere. We can not leave the car, and there is no great joy in exploring a planet unless you can really get out and stand upon its surface. Of course we can use altitude suits, and so make our explorations, but the temperature is so low, and the air so rare, we would be sure to need oxygen tanks and heaters.

	"The outer planets all have one big difficulty—there are so many asteroids in the ring of asteroids, we will be greatly menaced by them. And into the bargain they are so far away that I think we had best wait till later trips. That leaves the choice really between Mars, Venus, and Mercury. The choice as far as I see it is not very great. What do you vote?"

	"Well, I quite agree with you Arcot—it is more fun to explore an unknown planet than one that can be observed telescopically. I vote Venus," said Morey. Each of the others agreed with Morey that Venus was the logical choice.

	By this time the machine had sunk to the roof of their apartment, and the men disembarked and entered. The next day they were to start the actual work of designing the car!

-

	IT was late the next morning when they began their work, for it had been well after two when they finally reached the apartment. But when they had begun the job, it went forward steadily till the light faded that evening. So absorbed were they that noon and lunch hour passed unnoticed.

	"When we start this work," Arcot had begun, "we want to first design the ship for the conditions we expect to meet, and for the maximum convenience and safety. I believe I have thought of this trip longer than the rest of you, and for this reason I will give my ideas of what will give the greatest safety.

	"Venus is probably a younger planet than the earth. It is far nearer the sun than we, and gets twice the heat that the earth does. In the long-gone time when the planets were cooling I believe that Venus required far longer than earth, for the inpouring heat would tend to prevent its cooling. I imagine Venus today as a mighty world of rolling oceans of water, that beats on rugged shores of rocky islands, small spots of land in the vast watery area, while frequent fogs and mists swirl about the low hills, and through it all a tremendous oppressing heat burns down through the thick clouds. The surface temperature is probably about 150 degrees Fahrenheit.

	"There is little land, for Venus has no moon, and hence there has been no great tendency for the water to collect in any one place. The gigantic hollow that was left when the moon was torn free of earth made a great basin that caught the water, and left vast areas of land dry.

	"On Venus there was no such basin, and there is probably little dry land.

	"What life has developed must be largely aquatic, and the land is probably far behind in evolution. Then again—Venus is the planet of mystery-—we can only guess. But we do know what things we are going to need and what we will need to cross space.

	"Of course the main driving force will be the power units. These will get their energy from the rays of the sun by absorbing them in a great copper disc about twelve feet in diameter—the ship will have to be more of a disc than a cylinder. I think a ship a hundred and eighty feet long, fifty feet wide, and twenty feet deep will be about the best dimensions. The power units will be strung along the top of the ship in double rows—one down each side of the roof. In the middle of the roof will be a series of fused quartz windows, opening into a large room just under the outer shell of the ship. We will obviously need some source of power to activate the power tubes that run the molecular motion-power units. We will have a generator run by molecular motion-power units in here, absorbing its heat from the atmosphere in this room. The air will be heated by the rays of the sun of course, and in this way we will get all our power from the sun itself.

	"Lest this absorption of energy result in making the ship too cool, due to the radiation of the other side away from the sun, we will polish it, and thus reduce the unlighted side's radiation.

	"The power units will not be able to steer us in space, for they will all be on the roof, and those: on the sides, which will steer us in the atmosphere by the usual method, will be unable to get the sun's power; they will be shaded. For this steering in space, we will use atomic hydrogen rockets, storing the atomic gas by the Wade method in huge tanks in the hold. We will also have a battery down there for starting the generator and for emergencies. The air will be swept free of carbon dioxide by bubbling it through water under very high pressure, when the highly soluble carbon dioxide will remain in solution. It will be easy to keep the air clean and moist in this way, and at the same time remove the carbon dioxide into space. The water can, of course, be freed of the gas, and used again. Since we will have plenty of power, this system will be less bulky than the chemical absorption method, and more enduring. We will carry an emergency chemical plant however—-

	"The oxygen will be stored under very high pressure in tanks distributed all over the ship—anywhere so they will fill-in loose space that has no other use. We will carry a six months' supply. We will also carry an electrolysis outfit for turning water into oxygen and hydrogen. We can use the heat of Venus' atmosphere to run the generator and break up the water, then compress it and recharge the tanks, while the hydrogen will be broken into atoms, and used to recharge the atomic hydrogen tanks.

	"The most important single piece of equipment will be the apparatus for avoiding meteorites. There is really no tremendous number of them at this season, but we must be protected against them for it only takes one of them to finish us! The idea I had in mind was to take advantage of the usual form of radio altimeter, depending on the reflection of the radio wave from any material object. We can have a series of them scattered all about the ship—each pointing in a different direction. If anything comes within a hundred miles of us the altimeter covering that sector will at once set automatic machinery in operation, and the rockets will shoot the ship out of the path of the meteor. We will need greater accelerations than the power units can give us in space. Of course, in the air the power units are very powerful, but in space the sun will not supply heat very fast. The absorption discs will be made to lie flat to the side of the ship, of course, and painted dull black to absorb every bit of energy. In the air they will be fully efficient and have very little resistance, for they will cut the air like a knife."

	All that day Arcot and the other men discussed the various pieces of apparatus they would need, and toward evening Fuller began to draw rough sketches of the different machines, the mechanism that had been agreed upon.

	The next day, toward evening, they had really solved the rough details of the ship, but now began the greater task of calculating the stresses and the power factors.

	"We won't need any tremendous strength for the ship while it is in space, for then there will be little strain on it. It will be weightless from the start, and the gentle acceleration will not strain it in the least, but we must have strength, so that it can maneuver in the atmosphere.

	"Remember, when we leave earth we will do it by centrifugal force, for I can make much better speed in the atmosphere where there is plenty of power to draw on, than in space where I am dependent on the slow absorption of the sun's energy. We will start about the earth, forming an orbit just within the atmosphere, that is going at five miles a second. Then gradually we can increase the speed to about ten miles a second. At that speed the ship will tend to fly off the earth under its own centrifugal force; earth's gravity will no longer hold it. We will have to use the power units working downward to keep it from flying into space before we are ready. Then when we do release it, it will be entirely free of the earth, and no more work will be needed to overcome the earth's pull.

	"We are, on the earth, going 19 miles a second about the sun, so in space we would still be going at that rate, and would remain a captive of the mighty sun, rotating in the earth's orbit, yet not attached to earth, for any body rotating at 19 miles a second about the sun will automatically fall into the earth's orbit.

	"Venus rotates at 12 miles a second. To reach Venus we will not start toward it, but will use our acceleration away from it. This will allow the car in its rotation about the sun, and it will fall toward the center of attraction. The fall will, however, restore some of its speed, and a new orbit will be formed. This process will be continued, falling from orbit to orbit, till we at last fall into the orbit of Venus, and then we will let Venus catch us in its gravity, and we will fall to the planet. A similar process, reversed, would carry us to Mars. If we were to force the car toward the sun by means of the power units without slowing down its rotational speed, the moment we released the power, the ship would bounce back to the earth's orbit like a ball on the end of a rubber band!

	"When we leave earth—at ten miles a second, as I said—we will shoot off in the direction that will oppose the earth's movement, thus reducing our orbital speed of 10 miles a second, and causing us to fall in toward the sun. Of course we will gain speed again by the fall, so we will not fall beyond the orbit we want, but the trip will be tremendously shortened, and the higher the speed of leaving the earth, the quicker the trip." This came from Arcot.

-

	THE plans continued with exasperating slowness. The details of the work were amazingly complex, for all the machines were totally new. It was close to a week before even the power units could be ordered and the first work on the ship started. After that the orders for materials left the office daily. Still, it was late in November before the last order was sent out. Now they must begin work on other parts of the expedition—food supplies and the standard parts of the equipment. Also Arcot had decided to make a special ventilated suit. This was to make use of a small molecular motion director apparatus to cool the air, and blow it through the suit. The energy extracted by the apparatus in blowing the air about would cool it to a more comfortable temperature, for Arcot expected to find the temperature about 150 degrees, and so moist as to be unbearable, and eventually fatal to men of earth. The apparatus consisted of a small compressed air-driven generator and a power tube bank that could be carried on the back. It weighed, complete, about fifty pounds, but due to the lesser gravity of Venus this would be reduced to about 43 pounds, and that was but about fifteen pounds more than the difference that gravity would make on the weights of the men themselves.

	"Arcot," Wade had said when he saw the apparatus completed and the testing machine ready, "I was just noticing how similar that is to the portable invisibility apparatus I developed as the Pirate. I wonder if it might not be handy at times to be invisible—we could incorporate that with a slight change. It would not add more than five pounds, and those tubes you are using are easily strong enough to carry the extra load."

	The invisibility apparatus Wade mentioned was the electro-induction apparatus he had invented that past summer, and by which he had been able to enter the planes of The Transcontinental Lines unseen. It had been known that X-Rays penetrated metal by setting the molecules in rapid oscillation in step with themselves, then passing readily through the vibrating molecules. Wade had applied this principle to light—but in order to set up the vibration that made all substances perfectly transparent, he had used very short radio waves; the electrostatic conditions would set the molecules in vibration, and at once they were made perfectly transparent. The invisibility was almost perfect, and when the ship was in the air, it was utterly impossible to see it.

	"Great idea, Wade," said Arcot. "It might be very useful if we met some savages. The disappearance stunt would make us gods or something. And now that you mention it, I think we can install the apparatus in the ship. It will require almost no power, and might save our lives some time."

	Undoubtedly it was this simple suggestion of Wade's that led to the eventual salvation, not only of the expedition itself, but of two worlds.

	The work was going on steadily now at the great Transcontinental Shops where the machine was being made. The manufacture was being kept as much of a secret as possible, for Arcot feared the interference of the crowds that would be sure to collect, and since the ships directly adjoined the air field, it meant that there would be helicopters buzzing about the Transatlantic and Transcontinental planes.

	The work to be done required the most careful manipulation and workmanship, for one defect in space meant death. The trip would take them six days, and in the three days before they could reach either planet, much might happen to a crippled ship.

	To the men who were making the trip, the waiting seemed most exasperating, and they spent the days before they could begin the installation of the electrical apparatus in the completed hull in purchasing the necessary standard equipment, the standard coils, tubes, condensers, the canned food supplies, clothes, everything that they could imagine as of possible utility. They were making the ship with a great deal of empty storage space, for Arcot hoped the trip would be a financial success.

	The crust of the earth, that part of the earth that man can hope to use as sources of supplies, is built up of ninety-two elements. But of these ninety-two, seven account for more than 98 per cent of the material, one alone, oxygen, accounts for 50 per cent, and after oxygen comes silicon, which represents 28 per cent. The first seven elements are oxygen, silicon, aluminum, iron, calcium, magnesium, sodium and potassium. Of these seven elements, each one of which represents a higher percentage of the material than all the other eighty-five elements combined, there are three that man can use as building materials. Aluminum, iron, and magnesium are useful metals, but quartz, silicon dioxide, is the only other useful building material obtainable from that list. And not all of those 92 had been discovered in 2116.

	These small percentages of copper, zinc, lead, chromium, tungsten, beryllium, manganese, molybdenum, silver, platinum, and vanadium meant a starvation of metals. Platinum was exhausted already; iridium was gone; copper was nearly exhausted; silver was becoming more and more important as the other metals became rare; lead was now so rare that it was cheaper to line acid vats with silver than with lead.

	But there were many uses for which the metals were irreplaceable. Arcot hoped, with reason, that Venus might yield vast new sources of these nigh-exhausted metals. Our civilization is founded on metals, and it is only through them that it can remain strong. We must get new sources, or civilization will be lost. Arcot hoped to find such sources on Venus, and the ship was prepared to carry back samples of the ones found.

	On the outward trip some of this space would be filled with the many things that they would consume en route. In addition they were carrying a great many spare parts, spare tubes, spare power units, spare condensers—a thousand and one odd parts. Arcot intended that they should be able to make an entire new power switchboard and motion director unit if anything should go wrong, and he certainly had all the apparatus. As we know now, it was well he provided it.

	At last came the day when the last connection had been soldered, and the last joint welded. The atomic hydrogen tanks had been filled, and under the ship's own power the oxygen tanks were filled and the battery was charged. They were ready for a test flight!

	The great ship was standing on the floor of the shed now, waiting the start.

	"Oh fellows—come here a minute!" Arcot called to the other members of the party. "I want to show you something."

-

	THE other men walked quickly to the bow where Arcot was standing, and followed the line of his vision, looking in wonder to see that everything was right. They turned curiously to him, and he pulled from his coat a large glass bottle, sealed shut. "What's that for?" asked Wade curiously. "We are about to start on the first cruise, and I have been wondering if it isn't time we gave the machine a name?"

	"Great—I had been thinking of that too—what are we going to name her?"

	"Well," said Arcot, "I had been thinking of Alexander—he longed for other worlds to conquer!"

	"That's a good one—I have been thinking of naming it too—I guess we all have—but I was thinking of Santa Maria—the first ship to discover the New World," suggested Morey.

	"I was thinking more of its home," said Wade. "I was thinking of calling it Terrestrian."

	"Well—it's your turn, Fuller—you designed it. What do you suggest for your masterpiece?" asked Arcot.

	"I was thinking also of its home—the home it will never leave. I like to think that we might find people on Venus, and I would like to have a name on it that might be translatable into more friendly and less foreign terms—why not call it Solarite?"

	"Solarite—a member of the solar system—it will be that, always—it will be a world unto itself when it makes its trips—it will take up an orbit about the sun—a true member of the solar system. I heartily agree with that name." Arcot turned to the others. It was agreed upon unanimously.

	"But still I am curious about that glass bottle; it is so carefully sealed, rather imagine that there is some gas in there—but what is the object?" asked Morey with a puzzled smile.

	"Wrong—it hasn't any gas in it—which is the reason for sealing it so carefully. What more appropriate for christening a space ship than, a bottle of high-grade vacuum? 

	"We can't have a pretty girl christen this ship, that's sure. A flying bachelor's apartment christened by a mere woman? Never! We will have the foreman of the works here do that. Since we can't have the ship slide down the ways or anything, we will get inside and move it when he smashes the bottle. But in the meantime, let's have a symbol painted on the bow. We can have a blazing sun, with eight planets circling it, and the earth painted very much more conspicuously; below it we can have SOLARITE printed."

	The christening took place, and at last the ship was ready for the first trip into its natural medium—nothing. They were rising smoothly now, high into the air! At last they disappeared from the sight of the ground crew. It was shortly after noon when they left, but the sun was a great ball of fire low in the west when they returned, dropping plummet-like from the depths of space, the roar of the air about the hull, a long scream that mounted from a half-heard sound in the outer limits of the earth's atmosphere, to a roar of whining air as the ship dropped swiftly to the field and shot quickly into the hangar. Instantly the crew was running to the tide of the ship, as the door of the ship opened. Something was wrong!

	"Hey, Jackson—call the field doctor—Arcot had a little trouble out there in space!" In a moment the man designated was returning with the doctor, leading him swiftly down the long metal corridor of the Solarite to Arcot's room aboard.

	There was a mean-looking cut in Arcot's scalp, but it was not serious, though he had been knocked unconscious by the blow that made the cut.

	"How did this happen?" asked the doctor as he bathed the cut and deftly bandaged it.

	"There is a mechanism on board here that is designated to get the car out of the way of meteors while we are in space, and it works automatically. Arcot and I were just changing places at the controls. During the time while neither of us was strapped into the seats, a meteor came within range and the rocket tubes shot the car out of the way. We both went tumbling over to the side of the ship as it jumped, and Arcot landed on his ear. I was luckier, and was able to break my fall with my hands, and then land on my chest, but it was a mean fall—for under the great acceleration developed we had about double weight, so, though it was only about seven feet, we might as well have fallen fourteen," explained Morey. "We took turns piloting the ship, and Arcot, who started, was about to bring us back, when that shock just about shook us all over the ship. We will have to fix that!"

	The doctor was through now, and he began to revive his patient. In a moment he stirred and raised his hand to feel the sore spot. He was not yet fully conscious. In ten minutes he was conversing with his friends, however, slightly the worse for a very severe headache. The doctor gave him a mild opiate, and had him sleep off the effect of the blow in the car. The room where he was had been designed for his use, and was already fully equipped.

	"Doctor Bailey, would you like to look over the ship?" asked Wade.

	Naturally the doctor was quick to take the chance, and they started forward to the control room. Here the great fused quartz windows gave them a clear view in all directions except to the rear. There were five seats arranged in a semicircle before the main front window. The central seat was equipped with arms as broad as small tables, and on these arms there were instruments and controls. In the rear of the room was the main manual control board, its broad black surface dotted with dials and controls in a sequence unintelligible to the doctor.

	"This is the main control board here—the ship can be controlled entirely from this point. The control that we will actually use in most of the maneuvers, the speed control, the directional control, the ones that control our simple motions, are handled from the pilot set there. That is the system used in working while in the atmosphere when we will be turning quickly. In space, if we do take over the manual control, the machine will be controlled from this board. As a matter of fact the course will be worked out by the mechanical director apparatus downstairs. The power room is a combined chemistry and physics laboratory, and automatic control room. I will start the generator, and you can listen to the relays down there automatically adjusting to the load. At the same time you will hear it sucking air in through the vent to warm the molecular director power units that drive it. When in the atmosphere, it pulls in air to warm it—out in space it gets heat from the sun."

	They left the pilot room and walked on down the long corridor. On either side of the metal-walled hall there were rooms, and along the roof of the corridor there was a series of rungs like the steps of a ladder

	"What is the purpose of those rungs there?" asked the doctor curiously.

	"Those are for descending the ship in space. We will have acceleration forward only, and when we are it space the back of the ship is down. That is why I say the power room is downstairs—it is the last room in the ship. In space we actually slide down that pole there; it is easier and quicker. Holding on with one hand, we can break the hundred and twenty foot fall easily, for the acceleration, and hence our weight, will be very small. Did you notice that the beds are arranged to strap the sleeper in position? The changing acceleration would throw him all over if we didn't. The walls of the ship are made of steel, the usual tungsten iron alloy and are highly magnetic. The result is, it is easy to walk about by means of magnetic shoes. The side walls will be the floor, and that will complicate matters, but we thought it best to design the ship for maneuvering in the air of some planet, since it is fully automatic in space.

	"There are six bedrooms. There are only four going on this first trip, but that provides for future use. There is, of course, a kitchen also—but most of these rooms are storage rooms. There is a large battery just under the floor here, and beside it, filling in the curve of the ship, a large water tank. These are within the double walls of the ship, where it will be warm, to prevent the possibility of freezing them. We are expecting a warm climate on the planet Venus, so we are protecting the occupants of the ship from the heat while we are there by having double walls, with a vacuum in between. Hear that low hum? There are large gyroscopic stabilizers exactly in the center of the ship, holding it stable along all three axes, length, breadth and height"

	Arcot spent the night aboard the ship, to wake the next morning feeling fully recovered, while the wound in his scalp was fully healed now, by the action of the samvernite used in dressing it.

-

	THE ship was fully equipped now, and the time for leaving had been set for the following Saturday, three days off. There were great supplies of stores to be carried aboard in the meantime, and the men worked busily carrying the packages aboard, and storing them carefully. Great care had to be exercised in this work, lest the cargo slip free when the accelerations of the Solarite were varying, and batter itself to pieces, or even wreck some vital part of the ship. It was nearly noon Saturday before they could say that the first ship that ever was to leave the bounds of the earth's gravity was ready to start!

	Gentry the heavily laden ship lifted from the floor, and slowly it went out into the bright sunshine of the early February day. Beside it was riding the little ship that Arcot had first built, piloted by the father of the inventor of the ships. With him rode the elder Morey and a dozen pressmen. The little ship was badly crowded now as they slowly rose high into the upper reaches of the earth's atmosphere. The sky about them was growing dark—they were going into space!

	At last they reached the ultimate ceiling of the smaller ship, and it hung there while the Solarite went a few miles higher, then slowly, but ever faster and faster they were plunging ahead, gathering speed, they watched the radio speedometer creep up—1—2—3—4—5—6—stead-fly it was rising as the acceleration pressed them hard against the back of the seats—8 9 still it was rising as the hum of the generator back there became a low snarl—10—11—12—they were rocketing at twelve miles a second, the thin air about the ship was shrieking in a thin scream of protest as it parted on the streamlined bow. The vertical power units were driving the ship toward earth—still it hung on the centrifugal force—they seemed flung from earth with a weight of more than 300 pounds apiece. Even tins thin air offered considerable resistance at this terrific speed, and the thin air gave little heat so the power was low—still the speed rose slowly—and reached fifteen miles a second. Now the sun was really pulling them; they were falling toward the sun—away from the earth—the shrill screech of the air outside could not reach them through the vacuum walls, but there was a microphone on the outside that they might hear, and through the loud speaker in the control room came the thin wail of the air—then Arcot shouted to them in warning:

	"Hold on—we are going to lose weight—out into space!"

	There was a click, and a sudden sensation of falling—the ship seemed to reel beneath them—the angry snarl of the overworked generator died in an instant as the thudding relays cut it out of the circuit—they seemed falling with terrific and ever-increasing speed—they looked down—saw the earth shrinking visibly as they shot away at more than five miles a second—they were traveling fifteen miles a second ahead and five a second straight up. The men were watching with intensest interest as the heavens opened up to them—the air was left far behind, and they could see stars now a scant degree from the sun itself, for no air diffused his blinding glory. The heat of the rays seemed to burn them, there was a prickling pleasantness to it now, as they looked at the mighty sea of flame through smoked glasses. The titanic flames of the corona reached out like the arms of some flaming octopus through thousands of miles of space—huge arms of flaming gas that writhed out in vain attempts to reach and drag back the whirling planets to the parent body. All about the mighty sphere, stretching far into space, a wan glow seemed to ebb and flow, a flow of swift-changing color, mighty streamers of light that waved and fluttered a million miles in space. The colors seemed to flow with majestic slowness, but it was only the mighty scope of the thing that gave it this appearance, for these colors flashed about at close to the speed of light. It was the zodiacal light, an aurora borealis on a scale inconceivable!

	Arcot was working rapidly with the controls, the absence of weight that gave that continued sense of an unending fall, aided him and his assistants now in their rapid work of changing the controls from an air flyer to a space ship. The air scoop that had carried the air to the generator was closed off in a moment; there was a hiss of gas as the air was flooded into the room, and a moment later the hull vibrated with the acceleration of the generator as it again picked up speed. With the leaving of the air that warmed and drove it as they fell out into space, the machine had been robbed of its source of power, and it had stopped. Now again it was working smoothly, using the heat of the sun. The lights of the ship flashed on again as the machine gained speed, and they had some slight weight once more as the steady pull of the power units recommenced, the pull that would continue unceasingly till they at last fell into the atmosphere of Venus.

	At last the work was done and the ship was going on its way under the control of the instruments that would guide it across all the millions of miles of space and land it on Venus with the unerring certainty of a machine. The photo-electric telescopic eye was watching the planet constantly, keeping the ship surely and accurately on the course that would get them to the distant planet in the minimum of time.

	"Better start the ozonator, Wade—we don't want to get an overdose of ultra-violets! We will be able to look around in a minute—and for the next five days or so we will have the same things to look at!" said Arcot

	The ozonator was a simple apparatus designed to keep the correct amount of ozone in the air of the machine, for on earth there is a layer of the gas in the atmosphere that filters the sunlight to the same type of rays at all times, the type that the human body has become accustomed to. Through countless eons man has lived in this environment, and this is what he must have. Less, as was found out in the first half of the twentieth century would result in disease; more would result in burns.

	The ozone was the gas that regulated the supply in such a way that man had become accustomed to it. Had there been none, man would have developed an ability to adjust himself to changes in ultra-violet light just as he has become accustomed to changes in temperature.

	At last the work of preparing the ship for the trip was over, and the men could rest and use their time to observe the beauties of the skies as no man had ever seen them during all the billions of years of time that this solar system has developed—unless it be, as some think, that Mercury once had a population ere it became the desert waste it is, and that all of us, all in the solar system, are descendants of that long dead race.

	The lack of atmosphere made it possible to use a power of magnification that no terrestrial telescope may use.

	The blurred outlines produced by the shifting air prohibits magnifications of more than a few hundred diameters, but here in space they could use the greatest power of their telescope. With it they could look at Mars and see it more clearly than any other man had ever seen it, despite the fact that it was now over two hundred million miles away, and at times it comes to one sixth that distance from the earth.

	But though they spent much time taking photographs of the planets and of the moon, and in making spectrum analyses of the sun, they found the time passed very slowly. Day after day they saw measured on the clocks, but they stayed up, and found they needed little sleep, for they wasted no muscles. Their lack of weight made them lack fatigue. However, they determined that during the twelve hours before reaching Venus they must be thoroughly awake, so they tried to sleep in pairs just before coming near the planet. Arcot and Morey were the first pair to seek the arms of Morpheus—but Morpheus seemed to be a mundane god, for he did not reward them, and at last it became necessary to take a mild opiate, for their muscles refused to permit the tired brain to sleep. It was twelve hours later when they awoke, to relieve Wade and Fuller.

	They spent most of the twelve hours before them now in playing games of chess. There was little to be done. The silver globe before them seemed unchanging now, for they were still so far away it seemed little larger than the moon docs when seen from earth.

	But at last it was time for the effects of the mild drug to wear off, and for Wade and Fuller to wake soon from their sleep.

	"Morey—I wonder if it might not be interesting to observe the reactions of a man waking suddenly from sleep to find himself alone in space?" Arcot was staring thoughtfully at the control that would make the ship perfectly transparent, perfectly invisible. There was an expression of perfect innocence on his face—but a twinkle of humor in his eyes.

	"I wonder if it would?" said Morey grasping Arcot's idea. "What do you say we try it?" Arcot turned the little switch—and where there had been the ship, it was no more—it was gone!

-

	FULLER stirred uneasily in his bed, tight strapped as he was. The effects of the drug were wearing off. Sleepily he yawned—stretched, and blindly, his heavy eyes still closed, released the straps that held him in bed. Yawning widely he opened his eyes—with a sudden start he sat upright—then, after giving an excellent phonetic imitation of a wild Indian on the warpath, he leapt from his bed, and started to run wildly across the floor, his eyes raised to the place where the ceiling should have been calling lustily in alarm—then suddenly he was flying up—and crashed heavily against the invisible ceiling! His face was a picture of utter astonishment as he fell lightly to the floor—then slowly it changed, and took on a chagrined smile—he understood!

	He turned in amazement as loud cries suddenly resounded from Wade's room across the hall—then there was a dull thud, as he too, forgetting the weightlessness, jumped and hit the ceiling. Then the cries were gone, like the snuffing of a candle. From the control room there sounded loud laughter—and a moment later they felt more normal, as they again saw the four strong walls about them, and could again see the feet they stood on.

	Quickly they dressed now, and each stepped out into the main hall, just in time to meet each other.

	"Wade, did you hear those two morons up there? Such a sense of humor! Well, I suppose we must expect such things from them. I think it should be a lesson to us not to trust anything so valuable as this ship in the hands of a weak-minded pair like that again. One of us must always be on guard," said Fuller seriously—and rather loudly.

	Wade sighed heavily and shook his head.

	They were approaching the planet visibly now. In the twelve hours that had passed they had covered a million miles, for now they were falling into the planet under its attraction. It glowed before them now in wondrous splendour, a mighty disc of molten silver, far more beautiful than the moon ever was—a silver that made the moon a dull and tarnished globe in comparison. The strength of the reflected light was such that at their present distance of three quarters of a million miles it was almost uncomfortably bright. They could read a book with ease.

	For the last twenty-four hours they had been trying to reduce their speed relative to Venus, lest they be unable to form an orbit about the planet, and. shoot around it and back into space. Their velocity had been over a hundred miles a second part of the way, but now it had been reduced to ten. The gravity of the planet was urging them forward at ever increasing speed, and their problem was more difficult to solve.

	"We will never make it on the power units alone, out here in space," said Arcot seriously—"We will just shoot around it. I tell you how we can do it, though. We will go around it, entering its atmosphere on the daylight side, so that we won't be frozen to death in its shadow, and shoot into the upper limits of its atmosphere. There the power units will find some heat to work on, and we can really slow down. But we will have to use the rocket tubes to get the acceleration we will need to drive the ship into the air."

	There was a sudden clanging of a large bell—everyone dived for a hold, and held tightly. Not an instant later then there was a terrific wrench as the rocket avoiding mechanism threw the plane out of the way of a meteorite.

	"We are getting near a planet. That is the third meteorite we have met since we were more than a million miles from earth. Venus and earth and all the planets act like giant vacuum cleaners of space, pulling into themselves all the meteorites within millions of miles by their gravitational attraction,"

	Swiftly the planet before them was expanding—growing each instant vaster. It had changed from a disc to a globe, and now, as the molten silver of its surface seemed swiftly clouding, it turned grey; then they saw the true appearance, a vast field of rolling, billowing clouds!

	They were shooting about the planet now at ten miles a second, far more than enough to carry them away from the planet again, out into space once more if not checked.

	"Hold on everybody—we are going to turn toward the planet now!" Arcot depressed a small lever—there was a sudden shock, and all the space about them was a blazing furnace of huge, deep-red atomic hydrogen flames.

	The ship reeled under the sudden pressure, but the heavy gyroscopic stabilizers caught it, held it, and the ship remained on an even keel. Then suddenly there came to the ears of the men a long drawn whine, faint—almost inaudible—but there it was—the ship seemed slowing down. The loud-speaker was rapidly increasing its power—the Solarite was entering the atmosphere of a new world—the first machine that man ever made to thus penetrate the air of other worlds!

	Arcot was working busily now—quickly he snapped open the control that had kept the rocket flaming, turning the ship to the planet—driving it into the atmosphere—now they could get their power from the air that each instant grew more dense about them.

	"Wade—in the power room—emergency control post—Morey—control board there—hang on, for we will have to use some husky accelerations."

	Instantly the two men were diving for their posts—literally diving, for they were still nearly weightless.

	Arcot pulled another lever—there was a dull snap as a relay in the power room responded—then the lights wavered—dimmed—then in an instant the generator was once more humming smoothly—working on the atmosphere of Venus!

	Working feverishly now—they had but a short time to change back from space-ship to air-ship—in the atmosphere of a new world. In a moment the power units were again operating, and now they produced a force that made the men grasp their holds tightly, as they sucked a plenitude of power from the surrounding air.

	The loud-speaker had shrieked louder and louder, till it poured forth a deafening wave of sound. Now it was silent, for Fuller had opened the circuit. Around them the rapidly increasing density of the air made the whine grow to a roar—the ship was growing slightly warm from air friction, despite the extremely cold air at this altitude—more than seventy-five miles yet from the surface of the planet.

	They were dropping rapidly now—their radio-speedometer had fallen from ten to nine—then slowly, but faster and faster as more heat could be extracted from the air it had fallen 8—7—6—5—4—now they were well under orbital speed, falling under the influence of the planet, the struggle was over—the men seemed to loosen up, the ship was running quietly now, the smooth hum of the air rushing over the great power units coming softly through the speaker again, a humming melody in their ears—the song of a new world.

-

	SUDDENLY the blazing sun was gone—they were floating in a vast world of rolling mists—mists that struck the car with tiny clicks, which, in the millions of particles that were hitting each instant, summed up to a steady roar in the microphone.

	"Ice—ice clouds! We will drop down below the clouds, probably they extend for miles. Look, already they are changing—snow now—in a moment it will be water—then it will clear away—and we will be in the steaming air of Venus!"

	For ten miles—ten endless miles it seemed they dropped through clouds utterly impenetrable to the eye—then slowly the clouds became thinner; there appeared brief clear spots, spots into which they could see short distances—then here and there they caught glimpses of green below—was it water? or land?

	Then with a suddenness that startled them, they were out of the clouds, shooting smoothly along at one mile a second over a broad plain—it seemed to stretch for endless miles across the globe, to be lost in the far distance to the east and west, but to the north they saw a low range of hills that rose blue and misty in the distance.

	"Venus—We made it! The first men to ever leave earth—I'm going to start the old sender and radio back to them! Man—look at that stretch of plain!" Morey had jumped to his feet and was starting across the control room. "Lord—I feel like a ton of lead now—I sure am out of condition for walking after all that time just floating!"

	"Whoa—wait a minute there, Morey—you won't get anything through to them. The earth is on the other side of Venus now—it is on the night side, remember—we are on the day side. There are 7700 miles of rock and metal between here and the free space—then it has 45,000,000 miles or so to go before it hits the earth's atmosphere, and since you are using beam sending, it will have to penetrate the 8000 miles of earth before it reaches old New York. As I see it, we are now on the daylight side of this planet—which corresponds in time to the night side of earth. Thus, in about twelve hours we will be able to send a message. In the meantime, take the controls while I make a test of the air here, will you, Morey?" Arcot, relieved of the controls, rose and walked down the corridor to the power room where the chemical laboratory had been set up. Wade had already collected a dozen samples of air, and was working on them.

	"How is it—what have you tested for so far?" asked Arcot.

	"Oxygen and C02. The oxygen is about twenty-two percent, or, considering the slightly lower air pressure here, we will have just about the right amount of oxygen. CO2 is down to about one-tenth of one percent. That means that there must be a lot of animal life here considering the obvious plenitude of vegetable life.

	"But one thing surprises me, I had a piece of titanium ribbon in there—the oxygen I took out with phosphorus, and it won't burn. Titanium burns brilliantly in nitrogen, of course—in the earth's atmosphere the titanium will burn nearly as well after the oxygen is out as before. I can't get it—the atmosphere is O.K. for terrestrial life apparently; that mouse there is living quite happily."

	"Whatever the other seventy-five percent or so of diluting gas is, I don't know. Of course, I took out the water—passed it over calcium oxide. Magnesium ribbon won't burn in it, so it isn't any oxide—though I couldn't think of any it might be—if it were CO2 it would dissolve in the ocean at anywhere near that concentration. What do you make of it?" Wade was frankly stuck—it was beyond him.

	"Well—let's see. That mouse is living peaceably long enough—so it can't be very deadly—I think it would like to smell it." Arcot picked up the jar, and moved the glass cover to one side, and sniffed cautiously. "Quite odorless. I rather expected that—all gases that are reasonably inert are odorless. Is it very soluble in water? No, it can't be—there are large oceans here all right—fifty percent humidity and the temperature at five miles is one-ten! A hundred and ten degrees five miles up! I wonder what it's like at the surface—worse than Death Valley in July,"

"But let me see that gas again—what is the molecular weight of it?"

	"

	"Haven't made any careful measurements—couldn't with the ship jumping as it has been—but as near as I can tell it is about 35 or 34—nearer the 35."

	"Hmmm, allowing it is an element—if it isn't, either the magnesium or the calcium oxide should have done something to it—that means it isn't chlorine—we knew that anyway—but that has a molecular weight of 71; it can't be anything above that—wait a minute—of course—hooo—stupid—it's argon! No wonder it wouldn't attack magnesium or titanium! I wonder how we were so thick as to miss it! It is a little light—but I'll bet there is considerable nitrogen in it and that would make it come down toward 28, and probably there is a lot of helium and neon and the other inert gases in it. But what an atmosphere! No great amount of nitrogen; that means that life will have a sweet time extracting it from the air—but wherever there is life—it finds a way of doing the impossible. Test it more accurately, will you—you try for nitrogen and I will try the component inert gases."

	They ran the analysis rapidly, and in a very short time—less than an hour—their results stood at 23 percent oxygen, 14 percent carbon dioxide, 68 percent argon, 6 percent nitrogen, 2 percent helium, 5 percent neon, .05 percent hydrogen, and the rest krypton and xenon apparently. The analyses of these inert gases had to be done rather roughly in this short time, but it was sufficient to balance fairly accurately. On ionizing the gas in a small tube, they found that, unlike the bluish glow of earth's air it gave off a reddish grey color—a curious light of a ghostly hue.

-

	THE two chemists reported back to the control cabin. The others had been observing everything within range with the aid of the small telescope they had brought along. The hills seemed quite distant, but Arcot pouted out that it would be a very misty day on earth now, with such a high humidity. The slight difference in the radius of curvature of the sphere was, of course, unnoticeable.

	"Well, we will be able to breathe the atmosphere of Venus with ease. I believe we can go on now. I have been surprised to see no water in sight, but I think I see my mistake now. You know the Mississippi has its mouth further from the center of the earth than its source; it flows up hill! The answer is, of course, that the centrifugal force of the earth's spin makes it tend to flow in that way. Similarly, I am sure now that we will find that Venus has a vast belt of water about the middle, and to the north and south there will be two great caps of dry land. We are now on the northern cap.

	"We have the microphone turned way down. Let's step up the power a bit and see if there are any sounds outside," said Arcot and walked over to the power control switch. An instant later the loud-speaker was humming softly. There was a light breeze blowing. In the distance, though, forming a dull background for the entire hum, there came a low rumbling that seemed punctuated now and then by a greater burst of sound.

	"Must be a long way off," said Arcot, a puzzled frown on his face. "Swing the ship, around so we can see in what direction the sound is loudest," he suggested.

	Slowly Morey swung the ship around on its vertical axis. Without a doubt, something off in the direction of the hills was making a considerable noise.

	"Arcot—if that's a fight between two animals—two of those giant animals that you said might be here—I don't care to get near them!" Fuller was listening to the sounds, and looking off across the plain to the low hills in the blue distance.

	"If it is two animals fighting—we will leave this planet while we still can! Any animal that can make a racket tike that—well, I don't think it can exist!" Arcot was smiling to think of the size lungs that roar would require.

	The microphone was shut off while the Solarite shot swiftly forward toward the source of the sound. Quickly the hills were growing, the blue mistiness disappeared, and they showed as bleak harsh rock; but as they came nearer they saw over the tops of the hills now, flashes of light that intermittently came into being.

	"A thunderstorm! Ho—that's good—there is your animal. Fuller!" laughed Wade.

	"Not so fast, Wade—his animal is there—the only animal in all creation that can make a noise like that! Look through the telescope—see those dots wheeling about there above the flashing lights—there one got hit—there are no clouds there—no thunderstorm—the only animal that can cause that racket is man! There are men over there—and they aren't in a playful mood! Turn on the invisibility while we can, Morey—and let's get nearer!"

	"Men—look out—here we go!" Morey slipped a tiny switch set in one side of the instrument panel—then, before the relay below could move, he had flipped it back.

	"Here—you take it, Arcot—you always think about two steps ahead of me—you are quicker and know the machine better, anyway." 

	Quickly the two men changed places. 

	"I don't know about that, Morey," said a voice from the air—for Arcot had at once thrown the ship into invisibility—the ship was gone like the light of an extinguished candle. "The longer we stay here, the more mistakes I can see that we made in our calculations of what would happen. I see what put me off so badly on the estimate of the intelligence of people found on this planet! The sun gives it a double dose of heat—but also a double dose of X-Rays! Since about 1928 it has been known that X-Rays speed evolution. Just the same, we may be able to find friends here more quickly if we aid one. side or the other in the very lively battle going on there. Now, before we go any further, we want to decide whether or not to aid either side."

	"I think it is a fine idea. But which side are we to aid—and what are the sides. We haven't even seen them yet Let's go nearer and take a good look at them; certainly we ought to know that before we decide," said Fuller.

	"Yes—but are we going to join either side at all after looking?"

	"Oh, that's unanimous!" said Wade, excitedly. 

	Quickly the invisible ship darted forward. Soon they had passed the barrier of the low hills, and were again out on a broad plain. Suddenly all the men gasped in surprise! Well they might! There, floating high in the air, above a magnificent city, was a machine such as no man had ever before seen! A titanic airplane it was! Yet so monstrous, so gargantuan, that it beggared description. Fully three-quarters of a mile the huge metal wings stretched out in the dull light of the cloudy Venerian day; such a titanic machine it was that' it seemed to dwarf even the mighty city beneath! The roar of its mighty propellers came as a rumbling thunder to the Solarite. From it were coming the flashing bursts of flame. Now, on closer inspection, it was possible to make out what seemed a swarm of tiny gnats flying about the mighty plane. They seemed to be attacking the giant as vainly as the gnats might attack an eagle, and as foolhardily, for they could riot damage the mighty machine. Their flashing bombs that rained down upon it burst in blasts of yellow flame as harmlessly as so many firecrackers.

	All that mighty machine was covered with heavy metal plates, ten inches thick, and of metal so tough that when the powerful bombs hit it they were ineffectual, though they blew great craters in the soil below. Yet from it poured a steady stream of bombs that seemed to burst with a great flash of heat and light, and in an instant the tiny planes they struck darted down an incandescent mass of metal.

	Yet the giant seemed unable to approach the city—or was it defending it? No, for it was from the city that the vainly courageous little ships poured out. But certainly it was not these ships that kept the titanic battleship of the air at bay?

-

	CONSTANTLY the great ship was sending its bombs toward the city, only to have them fall short of it. But slowly, around the city, there was appearing an area of red hot, molten rock and dirt, and steadily this was moving inward as more and more shells from the great plane struck it. Then suddenly the battleship of the air turned toward the city and made a short dash inward on its circling path. Instantly it was apparent why the ship had not attacked the city directly, for up from the ground, a few hundred feet from the ring of molten rock, there leaped a long ray of hissing white flame. It reached up and seemed almost to touch the great machine. Then, as the titanic plane rolled, and side-slipped out of the way, it passed, harmless, a little shy of the monstrous wing.

	"Which? I say the city. No one should destroy so magnificent a city. Also they are losing, which will make our aid all the more welcome," suggested Arcot.

	"The city it is, I guess." All the others agreed, so Arcot started nearer. "But what in the world can we do to that huge thing? It has perfect invulnerability through size alone. It will be like attacking a battleship with a rowboat, as the old mariners would have said." Fuller was looking fascinatedly at the scene before him—though no one could tell just where he was gazing, since the entire ship was as invisible as air.

	Now it seemed that one of the men of the city had a system to wreck the giant plane—the mighty propellers. There were fifty of these strung along each of the titanic wings; the giant monoplane seemed to be vulnerable only there—for if enough of these could be broken, eventually they would be able to blow holes in its armor, while it lay helpless on the ground. They had apparently tried to bomb the gigantic metal blades, but the rushing, swirling air currents had thrown the bombs aside, or smashed them against the thick armor. Now one of the little planes darted forward and dove at full speed directly against one of the propellers! But the sacrifice was in vain—there was indeed a terrific crash—one that made the loud speaker in the invisible Solarite tremble. Yet the mighty blades were functioning as smoothly as ever!

	Indeed, it seemed that the Solarite would be as utterly helpless as any against that titanic machine. Now Arcot was climbing the machine high into the sky above the great plane. There was a full mile drop between them when he released the sustaining force of the Solarite and let it drop, straight toward the source of the battle-falling freely, ever more and more rapidly; they were pushing at the mighty plane below at a pace that made their hearts seem to pause—then suddenly Arcot cried out, "Hold on—here we stop!"—they seemed a scant hundred feet from the broad metal wings of the great plane, which was hanging beneath them, totally unaware of the Solarite. Then suddenly there was a tremendous jerk, and each man felt himself pressed to the floor of the machine with a terrific weight that made their backs crack with the load. Almost unconscious they seemed. Below them was nought but a mighty sea of roaring red flames—a hell of blazing gas that roared like a million bombs at once. The Solarite was sitting down on the rockets! All six of the rocket tubes in the bottom of the car had been opened wide, and streaming from them in a mighty blast of incandescent gas, the atomic hydrogen was shooting out in a mighty column of gas at 3500 degrees centigrade. In an instant the great plane was incandescent where the gas touched it, and in an interval so short that it was almost immeasurable, the fall of the Solarite had been checked, and it was rebounding high into the air again. As soon as Arcot could, he reached a hand that was weighted down with the load of six gravities and pulled shut the little control that had sent those mighty torches flaming out. Then an instant later they were racing ahead lest the plane shoot bombs toward the gas columns.

	Then at last they were able to look at their work! No longer did they see the mighty plane unscathed, invulnerable, for now there glowed six great craters of incandescent metal that almost touched and coalesced. The great plane itself was reeling, staggering, plunging downward, but long before it reached the hard soil below it was brought out into level flight, and limping, for several of its engines were dead now, it circled and made off toward the south. The horde of small planes followed, dropping a rain of bombs into the glowing boles in the ship that made them grow swiftly larger. But now the men of the ship had to a large extent recovered from the shock of the attack and were fighting back. In a moment—just before the ship passed over the horizon and out of sight, the Terrestrians saw the great props that had been idle, suddenly leap into life, and in an instant the giant had left its attackers behind—fleeing, wounded from its invisible foe.

	It was agreed that they return to the city and become visible.

	Again they turned, and slowly went back, still invisible, to the approximate spot where they had destroyed the invulnerability of the Giant. Then suddenly, out of nothing, the Solarite appeared. In an instant a dozen of the tiny two-man planes were darting toward it. Just that they might recognize it, Arcot shot it up a bit higher with the aid of the keel rockets at one-third power. Still, the typical reddish flame of atomic hydrogen was instantaneously recognizable.

	Little these planes were, but shaped like darts, and swifter than any plane earth had—they shot along at 1000 miles an hour readily, as Arcot soon found out. It was not a minute before they had formed a long line that circled the Solarite at minimum speed, then started off in the direction of the city. On impulse Arcot followed after them, and instantly the planes shot their velocity up. It was quickly indeed that they reached a thousand miles an hour, and rocketed smoothly along.

	The city they were approaching was an inspiring sight—mighty towers that reached their graceful lines a half mile in the air, their sides of brightly colored material of some kind gleaming in warm hues seemed to make the entire city a gigantic jewel—one lone piece of architecture, for here no individuals were looming out. There was no irregular skyline, but every unit tended toward the gigantic edifice that rose, its gleaming tower of black and gold a full half mile in the air.

	The outer parts of the city were evidently the residential districts, the low buildings and wide streets with the little green lawns showing the care of the individual owner. Then came the apartment houses and the small stores; then they rose in gentle slopes, higher and higher, towering at last to a mighty pinnacle of beauty—a single resplendent jewel of flashing color, designed as a whole, and not in a multitude of individually beautiful, but in harmonious units, like some wild mixture of melodies, each in itself beautiful, but mutually discordant.

-

	NOW the Terrestrians were following their escort high above these great buildings, following them to the great central tower. In a moment they were above it, and in perfect order the ships of the Venerians shot down to land smoothly, but at high speed. On the roof of the building they slowed with startling rapidity, held back by electromagnets under the top dressing of the roof landing, as Arcot learned later.

	"We can't land on that—this thing weighs too much—we'd probably sink right through it! I'll go down into the street there and land—it looks wide enough!" Arcot maneuvered the Solarite over the edge of the roof, and then dropped it swiftly down the half mile to the ground below, just above the street level he held it up, and lowered it gently, giving the hurrying crowds plenty of time to get from beneath it.

	Then, in anxious curiosity, he landed it, and looked quickly at the crowd of Venerians who had gathered in the busy street, coming out of the buildings where they had, no doubt, sought shelter during the raid. It was a rapidly growing crowd as the Terrestrians looked interestedly at these people of a new world—a people that no man had ever seen.

	"Why," said Fuller in startled surprise, "they look almost like us!"

	"Of course," laughed Arcot—"and what did you expect. There are certain prerequisites that any intelligent creature must have. He must have a brain, of course, but also he must have tools, for that is the only way the intelligence of the brain may be expressed. To not only give him those necessary tools, but also to permit him to hold his brain case more out of harm's way, and get a wider range of vision, he stands on his hind legs, thus freeing his forelegs for work.

	"The first requisite of any animal that is to rule the planet of his home, is that he have physical strength enough to cope with the problems about him. He must be strong enough to fight his enemies. But since he also has intelligence, he must be strong enough to use the tools he makes. It would seem an elephantine beast was the obvious candidate for intelligence—but he isn't. On earth, Nature tried out the giant reptile and discarded it. He was so big he didn't have to develop intelligence, perhaps. Then the insect—Nature tried that—developed intelligence there—but it was so small, that it couldn't do much toward changing the face of the earth to suit itself, so it, too, was put aside. Then, in a creature half way between the two, Nature found the best possibilities. But the greatest asset she gave man was the thumb; with it he is able to hold the tools he makes, among many other things, and it is the thing that has done most toward developing man's intelligence.

	"But further on the question of size. If man was much bigger, he would be fragile. Can you imagine an elephant jumping? No, he couldn't; he would break his legs under his own weight if he did. A thing that size can't be agile as Man had to be.

	"But here, on this planet, we have a lesser gravity, and to the degree of that lesser gravity the animals could be larger than those of earth, without exceeding the breakage limit. I think that explains the size of those Venerians."

	Certainly it needed some explanation, for in all that crowd, only the obviously young were under six feet. The average seemed to be seven feet, with rather large chests—well-built men and women, who would have seemed very much human indeed, but for a ghastly, death-like blue tinge to their skin. Even their lips were as bright a blue as man's lips are red. The teeth seemed to be as white as any human's, but their mouths were blue.

	"Why, they look as if they had all been eating blueberries!" laughed Wade. "I wonder what makes their blood blue? I have heard of blue-blooded families, but these are the first I have ever seen!"

	"I think I can answer that, also—I have been reading about various forms of life recently," said Morey slowly. "It seems odd to us—but those people have their blood based on hemocyanine. In us, the oxygen is carried to the tissues, and the carbon dioxide carried away by an iron compound, hemoglobin, but in many animals of earth, the same function is performed by a copper compound, hemo-cyanin, which is an intense blue. I am sure that that is the explanation for these strange people, By the way, did you notice their hands?"

	"Yes, I had. I know they are different from ours, but I haven't had a good look at them and can't say in what way they are different. They strike me as having one too many fingers—look—there—that fellow is pointing—why—his hand has not too many fingers, but too many thumbs! He has one on each side of his palm! What good does that do him—let's see, if I put one hand on top of the other, palm to back, I get the same effect—say it would be handy in placing nuts and bolts, and such fine work, would it not?"

	Suddenly a lane opened in the crowd, and from the great black and gold building there came a file of men in tight-fitting green uniforms, a file of seven-foot giants. Obviously they were soldiers of some particular branch, for in the crowd there were a number of men dressed in similar uniforms of deep blue.

	"I think they want one or more of us to accompany them. Let's flip a coin to decide who goes—two better stay here, and two go. If we don't come back inside of a reasonable period of time, one of you might start making inquiries; the other can send a message to earth, and get out of harm's way till help can come. I imagine these people are friendly now, however—else I wouldn't go."

	As Arcot finished, the leader of the troop stepped up to the door of the Solarite, and coming to what was obviously a position of attention, put his left hand over his right breast in an equally obvious salute, and waited.

	The coin was flipped with due ceremony—it was to decide which of them were to have the distinction of being the first Terrestrians to set foot on Venus. Arcot and Morey got the luck, and they quickly put on the loose-fitting ventilated cooling suits that they might live comfortably in the hot air outside—for the thermometer registered 150!

	The two men quickly walked over to the entrance door of the air lock, entered, closed it behind them, and opened the other door. There was a slight rush of air as the pressure outside was a bit lower than mat inside. At once there was a singing in their ears, and they had to swallow several times to equalize the pressure. The guards at once fell into a double row on either side of them, and the young officer strode ahead. He himself had curbed his curiosity after the single startled glance he had given these strange men. Only their hands were visible, for the cooling suits covered them almost completely, but the strange pink color must indeed have been startling to his eyes; also their dwarf stature, and the strange suits they wore. The men of his little troop, however, as well as the people in the crowd about them, were not so disinterested. They were looking in eager amazement at these men who had but just saved their city, these strange small men, with their queer pink skin. And most surprising of all, perhaps, the inner thumb was missing from each hand!

	But soon they had passed beyond the sight of the crowd, which was held in check by a handful of the deep blue uniformed men.

	"Those fellows would never hold such a Terrestrial crowd back if visitors from another planet landed!" remarked Morey wonderingly.

	"How do they know we are visitors from another planet? We suddenly appeared out of nowhere—they don't even know our direction of approach. We might be some strange race of Venerians as far as they know, though their swift planes must have carried them over all Venus long before now!" Arcot replied.

	They had walked quickly up to the great gold and black entrance, and passed through the great doors that seemed made of great masses of solid copper, painted with some clear lacquer that kept the metal lustrous, the rich color shining magnificently. They stood open wide now, as indeed they were always. To these men of a copper starved world, where copper was practically as dear as silver, this seemed a tremendous investment. Even the giant Venerians were dwarfed by these mighty doors as they passed through into an equally vast hall, a mighty room that must have filled all the front half of the ground floor of the gigantic building, a hall of graceful columns that hid the great supporting members. The stone, they knew, must serve the Venerians as marble serves us, but it was a far more handsome stone. It was a rich green, like the green of thick, heavy grass in summer when the rain is plentiful, rich and thick, a soft wavy green. The color was very pleasing to the eye, and restful too. There was a checker-board floor of this green stone, alternated with another, a stone of intense blue. They were hard, and the colors made a very striking pattern, pleasingly different from what they had been accustomed to, but common to Venus, as they soon learned.

	Arcot dropped quickly to one knee, and started to examine the green stone closely, felt of it an instant, then jumped up in surprise, shaking his hand; a moment he looked surprised—puzzled. Then he laughed. The guards who had been accompanying them had halted, and were watching them with interest and amusement—examining the material of a common floor!

	"Why—I forgot—I won't again, though—look out that you don't touch anything unnecessarily, Morey—everything here is at a temperature of 150 remember, and is most unpleasantly hot. I almost burned my hand! It was more surprise than anything else that made me jump, but I think I know what that green stone is—it's chromic carbonate in some natural form that we don't have on earth. These fellows might just as well say that a stone, such as marble, couldn't exist, because they had never seen it—and man has never yet duplicated the work of nature in making Iceland spar—crystallized calcium carbonate, yet it is chemically the same as limestone! But let's move on—they are obviously waiting for us."

-

	THERE were many soldiers in the great hall that they were crossing, and as the little party walked on, they stopped and looked in surprise at the strangely hooded figures.

	At last the party had crossed the great hall, and stopped beside a large doorway. The officer stopped for a moment, pointed out two of his men, who remained, while the others walked quickly away. The diminished party stepped through the doorway into a small room whose walls were lined with copper apparently, and an instant later, as the officer pushed a small button, there was a low hiss of escaping air, and a copper grating sprung quickly up across the opening of the elevator. Then another button, and there was the familiar sinking feeling as the car rose, a low hum seeming to come from the lower part of the car.

	The car rose swiftly through a very considerable distance—up—up. It seemed that no car could work over that great climb.

	"They must have some wonderfully strong cables here on Venus!" Morey exclaimed. "The engineers of the Terrestrial buildings have been wondering for some time how to get around the difficulty of shifting elevators. The idea of changing cars doesn't appeal to me, either—but we must have risen a long way!"

	"I should say so—I wonder how they do it. We have been rising for a minute and a half at a very fair clip—there we are—I want to look at this car!" Arcot at once stepped over to the little row of buttons on the control board, looked at it closely, then stepped out quickly and peered down between the car and the shaft as the copper grating fell, simultaneously pulling down with it the door that had blocked off the hall-way.

	"Come here, Morey—simple system at that! It would be so, of course—look—they have tracks, and a regular trolley system, with cog rails alongside and the car just winds itself up! They have an electric motor underneath, I'll bet, and just run it up in that way. They have never done that on earth because of the terrible cost of running the car up without any counterbalance—it would be too expensive—require too much power. I think I see the solution—the car has electro-dynamical brakes, and going down, just slows itself down by pumping power into the line to haul some other car up. This eliminates the difficulty of cables that can't carry their own weight very nicely. The counterbalance means that at least a mile of cable must be used in raising the car one-half mile, actually some six miles of wire cable—this is a mighty clever scheme!"

	As Arcot straightened, the officer beckoned to him to follow, and started down the long corridor which was lined on either side with large doorways, on which there was painted in black characters some inscription, evidently the directory of the floor.

	Through a long series of the branching corridors they at last reached one that had but one exit, into a large office, into which the young officer led them. Immediately he snapped to attention, spoke briefly and rapidly, saluted and retired with his two men.

	The man before the Terrestrians now was a tall, kindly faced old gentleman, his straight black hair was turning slightly to a very light blueish, almost a grey, in spots, but the kindly face, the smiling eyes, and an air of sincere interest seemed to illumine the entire countenance. He looked curiously, questioningly at the two men before him, looked at their hands, his eyes widening in surprise; then he stepped quickly forward, and extended his hand, at the same time looking toward Arcot.

	At once Arcot understood him and extended his hand. The Venerian took it in his hand—then with an exclamation on the part of each, they mutually released each other, for Arcot felt a decidedly uncomfortable degree of heat, almost scaldingly hot, just as the Venerian felt a degree of intense cold! Each seemed staring from his hand to the hand of the other in surprise, then a smile lighted the face of the Venerian as he very emphatically put his hand at his side. Arcot smiled at him, and said to Morey in an animated tone:

	"They have a body temperature of at least 170 Fahrenheit. It would naturally be above room temperature, which is 150 here, so that they are most unpleasantly hot to us. Many forms of earth-life would be killed by that temperature, but there are, of course, different forms of life here on Venus, modified to stand that temperature as natural. I hope these fellows don't have fevers! They would be apt to boil over!

	"But really they have some 40 degrees leeway, and as the temperature of the human body varies never more man eight degrees, they are safe enough, I guess."

	"But they must have to boil all their food under increased pressure here; a difference of 40 degrees would probably be insufficient!"

	The Venerian had picked up a small rectangle of black material, smooth and solid. With it as a tablet he drew quickly on it with a pencil of copper, apparently. In a moment he handed the tablet to Arcot, who reached out for it, then thought better of it, and motioned that he didn't want to burn his fingers. The old Venerian held it where Arcot could see it.

	"Why, Morey, look here—I didn't think they had developed astronomy to any degree, because of the constant clouds, but just look here. He has a nice little map of the solar system, with Mercury, Venus, Earth, the Moon, Mars, and all the rest on it. He has drawn in several of the satellites of Jupiter and of Saturn too."

	The Venerian pointed to Mars and looked inquisitively at them. Arcot shook his head and pointed quickly to earth. The Venerian seemed a bit surprised at this, then thought a moment and nodded his head in satisfaction. He looked at Arcot intently a moment. Then to Arcot's amazement, there seemed to form in his head a thought—at first vague; then quickly it took on definite form.

	"Man of Earth," it seemed to say, "we thank you—you have saved our nation"—(there seemed to be a name idea here, but a name is merely a phonetic symbol for a country, just as a flag is its material symbol. It can not be impressed on the brain of one who has different physical arrangements, as can an idea, for ideas are everywhere the same.)

	"We want to thank you for your quick response to our signals. We had not thought that you could answer us so soon." The Venerian seemed to relax as the message was finished. It was obviously a great effort.

	Arcot looked steadily into his eyes now, and tried to concentrate on a message—on a series of ideas. To him, trained though he was in deep concentration on one idea, the process of visualizing a series of ideas was new, and very difficult. But he soon saw that he was making some progress.

	"We came in response to no signals—exploration only—we saw the battle—and aided because your city seemed doomed, and because it seemed too beautiful to be destroyed."

	"What's it all about, Arcot?" asked Morey in surprise, as he watched them staring at each other.

	"These Venerians have developed telepathy to a practical point—it seems I am terribly thick from his point of view, but I just learned that they sent signals to earth—why, I haven't learned—but I am making progress. If I don't get a headache or go insane from the overwork, I will find out sooner or later—so wait and see." He turned again to the Venerian who was now looking at him rather dubiously. Then quickly he turned to his desk, and pulled a small lever down. Then again he looked intently at Arcot.

	"Come with me the strain of this conversation is too great—I see you do not have thought transference on your world."

	"Come along, Morey we are going somewhere. He says this thought transference is too much for us. I wonder what he is going to do?"

-

	OUT into the maze of halls they went again, now led by the kindly, seven-foot Venerian scientist. Down through a long series of halls they went, till at last they reached a large room, where already there had gathered in the semicircle of seats a hundred or so seven-foot Venerians. Before them, on a low platform, there were two large chairs with deep cushions. To these chairs the two Terrestrians were led.

	"We will try to teach you our language telepathically. We can teach you the ideas—you must learn the pronunciation, but this will be very much quicker. Seat yourselves in these chairs and relax."

	The chairs had been designed for seven-footers. These men were six feet and six feet six, yet it seemed to them, as they sank into them, that never had they felt such comfortable chairs. They were designed so that every muscle and every nerve should be at rest. Now they seemed floating in space once more, without weight. Suddenly Arcot felt a wave of sleepiness oppress him; then slowly he grew more and more sleepy—he was tired—tired. It seemed that suddenly visions began to fill his mind-visions as he regained consciousness slowly—up from the dark, and into a dream world. It seemed he saw a mighty fleet of gargantuan planes flying above the city where he was—a fleet whose individual planes were a mile long, three-quarters of a mile wingspread—titanic monoplanes, whose droning roar as the hundreds of : whirling props stirred the air seemed to roar through all space. Then suddenly they were above him, and from each there spurted out a great stream of dazzling brilliance, an intense glow that reached down, and touched the city—There was an awful concussion in his ears. All the world about him was gone in a flash of awful brilliance; then all was dark.

	Another vision it seemed now—a vision of the same fleet hanging over a giant crater of molten rock, a crater that nestled on a plain beside low green bills—a crater that he knew had been a city. The giants of the air circled, turned, and sped far off over the horizon—Again he was with them—and again he saw a great city fuse in a blazing flash of blinding light—then again and again—around all that world he seemed to see smoking ruins of great cities, blasted red hot rock that had been cities, a world of awful desolation. Then he was with the Destroyers, riding up, up, up—out of the clouds they were, out beyond the swirling mists, where the cold of space seemed to reach in at them, and the roaring of the mighty propellers was a thin whine—then suddenly that was gone, and out of the rear of each of the titanic machines there burst a great stream of light, a blazing column of light that roared back, and lit all space for miles around—then the machines were shooting up, and away—out across space—away from the planet—on—on. Then he seemed to see them nearing another world, a world that shone a dull red, but he saw the markings and knew that it was earth, not Mars. The great planes were falling now—falling at an awful speed into the upper air of the planet, and in an instant the great light flares were gone, fading and becoming weaker as the dense air oppressed them. Now again there came the roar-of the mighty propellers. Then swiftly the Fleet of Giants was dropping, and Arcot saw it sink lower and lower; his vision saw it coming above a spot he knew must be New York—but it was a strangely distorted New York; it was a Venerian city, where New York should have been—and again he saw great bombs falling. In an instant the gigantic city was a smoking ruin—then the visions faded, and slowly he opened his eyes, looked about him. He was still in the room of the circle of chairs—he was still on Venus—then suddenly to him came the meaning of these visions—the meaning of that strangely distorted New York, of that red earth. It meant that this was what the Venerians believed was to happen! They were trying to show him the plans of the owners and builders of those gigantic ships! The New York he had seen was the New York as these men imagined it

	Startled, confused, he rose unsteadily to his feet His head seemed whirling in the throes of a terrific headache. The men about him were looking anxiously at him—he glanced toward Morey. He was sleeping deeply in the seat—now and then his face moved in some strange expression. It was his turn now to learn this new language and see the visions.

	The old Venerian, who had brought them here, walked up to Arcot and spoke to him in a softly musical language, a language that was sibilant and predominated in liquid sounds; there were no gutturals, no nasals; it was a more musical language than earth men had ever before heard, and now Arcot started in surprise, for he understood it perfectly; the language was as familiar as English.

	"We have taught you our language as quickly as possible—you may have a headache, but you must know what we know as soon as possible. It may well be that the fate of two worlds hangs on your actions.

	"These men have concentrated on you and taught you very rapidly, given you those visions of what we know to be in preparation. You must get back to your wonderful ship as quickly as possible; no time can be lost, and you must know what has happened here on our world in the last few years, and what happened twenty centuries ago.

	"Come with me to my office, and we will talk. When your friend has also learned, you may tell him." 

-

	QUICKLY Arcot followed the Venerian down the long corridors of the building. Few people they met, and these seemed intent on their own business, paying little attention to the strange man that walked through the halls with the tall old gentleman.

	At last they were again in the office where Arcot had first seen the Venerian. They sat down, and Arcot listened to a new history—the history of another planet 

	"Twenty centuries ago," the old man began /'there were two great rival nations on this planet. The planet Turo is naturally divided so that there would be a tendency thus to form two great nations. There are two enormous belts of land around the globe, one running from about twenty degrees north of the equator to about eighty degrees north. This is my country, Lanor. To the south there is a similar great belt of land, of almost identical size, Kaxor. These two nations have existed for many thousands of our years—slightly over two-thirds of the time in your years—and two thousand years ago there was a great crisis in the affairs of the world—a great war was in process of starting—but a Lanorian developed a weapon that made it impossible for the Kaxorians to win—and war was averted. The feeling was so strong, however, that laws were made that have been able to stop all intercourse between the two nations for these thousands of years. Only we know that Kaxor has studied the principles of physics, perhaps in hopes of finding a weapon with which they could threaten us once more. Lanor has studied the secrets of the human mind, and of the body. We have no disease here any longer; we have no insanity. We have studied chemistry greatly, but physics only in connection with our other studies. Recently, however, we have again taken up the study of this science, since it alone of the mam sciences had gone neglected. But twenty-five years have been spent on these researches, and in that short time we cannot hope to do what the Kaxorians have done in two thousand. The secret of the heat ray, the weapon that prevented the last war, had been nearly forgotten. It required diligent research to bring it to life again, for it is a very inefficient machine—or was. Of late, however, we have been able to improve it and now it is used in commerce to smelt our ores. It was this alone that allowed this city to put up the slight resistance that we did. We were surely doomed. This is the capital of Lanor, Sonor. The nation would have fallen but for you.

	"We have had some warning that this was coming. We have spies in Kaxor now, for we learned of their intentions when they flew one of the giant planes over one of our cities and dropped a bomb! We have been trying, since we discovered the awful scope of their plans, to send you a warning if you could not help us. That you should come here just now is one of the greatest things of the universe—a chance in a billion billion billion, I suppose—but perhaps there is more than chance behind it? Who knows?

	"But since that plane has been driven away, we can expect at any moment a new raid, and we must be prepared. Is there any way you can signal your planet?"

	"Yes—we can signal easily by—I do not know the word in your language—it may be that you do not have it—radio we call it—it is akin to light, but of vastly longer wavelength. Produced by electrical means, it can be directed like light by means of a reflector and sent in a beam. It can penetrate all substances except metals, and can leak around them, if it be not directional. With it I can talk readily with the men of earth, and this very night I will. But I want to learn of your planet. I will be able to warn our planet, but I will also want to tell them of yours. There is much to be gained by a knowledge of your planet and its resources!

	"You say your people have studied chemistry. We have, too. And we have studied physics much, but we have studied the mind very little. The body we have studied, and we know enough to care for it. We, too, have well nigh eradicated diseases. But we have had a civilization of metals for many years now, and there are many metals we lack. This trip to your planet was partly in interest of finding more supplies.

	"Here you use copper very lavishly. Is it plentiful?"

	"On Turo," said Tonlos, "we have two elements which constitute a very large percentage of the available resources. Oxygen constitutes forty-two percent, and silicon about ten percent

	"Next in abundance is 'morlus,' which constitutes about 7 percent."

	"Morlus—I have the word in your language—but I do not know the element. What is it?" asked Arcot.

	"Why—here is some!"

	Tonlos handed Arcot a small block of metal that had been used to hold a thin sheet of metal flat on a table in one corner of the room. It seemed a fairly dense metal, about as heavy as iron, but it had a remarkable blueish tint. Obviously, it was the element that composed the wings of the airplane they had seen that afternoon. Arcot examined it carefully, handicapped somewhat by the fact that he could not hold it directly, but only on a piece of cloth, since the metal was too hot. He picked up a small copper rod and tried to scratch it, but there was no noticeable effect

	"You cannot scratch it with copper," said Tonlos, "it is the second hardest metal we know—it is less hard than chromium, but far less brittle. It is malleable, ductile, very strong, very tough, especially when alloyed with iron, but those alloys are used only in very particular work, for iron is very rare. We have—"

	"Iron is rare!" exclaimed Arcot in surprise. "Why, on earth it is exceedingly plentiful. I cannot understand how it can be so rare here on Venus. And I cannot identify this element. May I take it to the ship to test it?"

	"You may, by all means. I thought from the appearance of some of your mechanisms that iron was very plentiful on your planet. But, from the fact that you do not recognize this metal of ours, I see that to you it is rare. You will have considerable difficulty getting it into solution. It is attacked only by boiling selenic add, and that dissolves platinum readily. However, it is related to manganese. The usual test for the element is to so dissolve it, oxidize it to an acid, then test with radium selenate, when a brilliant greenish blue salt is—"

	"Test with radium selenate! Why we have no radium salts whatever on earth that we could use for that purpose. Radium is exceedingly rare!" said Arcot.

	"I think I had best go on with my list," Tonlos continued. "Radium is by no means plentiful here, but we seldom have to test for morlus, and we have plenty of radium salts for that purpose. We have never found any use for radium—it is so active that it combines with water just as sodium does, it is very soft—a useless metal, and dangerous to handle. Our chemists have never been able to understand it—it is always in some kind of a reaction no matter what they do, and still it gives off that very light gas, helium, and a heavy gas niton, and an unaccountable amount of heat.

	"Next after morlus in quantity comes copper, then chromium, then calcium, beryllium, sodium and potassium, and lead, zinc and tin, all occuring over one percent Then the non-metals break in again—the most plentiful is carbon—then comes another metal, tungsten, .9 percent; then there is a long string of metals and non-metals that occur in very small quantities except for sulphur, selenium and platinum.

	"We have large supplies of platinum really—they all seem to come in lumps, not like some of them, that are spread out all over."

	"But how about aluminum? and gold? and the halogens?" asked Arcot.

	"Oh, aluminum is rather rare—we use it as a monetary standard—it is hard enough to make good coins. It seems a pity it is so rare; it is a very useful metal. And what surplus there is is used as ornaments by women and in very expensive things. It is a luxury which would make a very useful necessity if it were more plentiful. Gold—oh, yes—I had forgotten it. It is always bothering the platinum workers—and it occurs all over, it seems. It is a terrific nuisance. It is not exceedingly plentiful—less than half of one percent—but widely distributed. It is soft and sticky, so to speak. It clogs up things, and is no use whatever. It is too soft to hold, together. We have tried to use it for plating since it is non-corrosive, but it wears off right away. It won't stand heat, so we can't use it in the laboratories. We have tried using it in add chambers, but it 'poisons' many catalysts and keeps them from working properly. We cannot use it near the platinum catalysts in the sulphuric acid plants—so we use lead all over. We do use it in the concentrating pans sometimes—but it isn't worth the trouble of digging it out of the ground and hauling it here. I don't believe anyone has ever tried to develop a use for it, though it is plentiful enough I suppose. It is naturally very cheap, and unscrupulous people use it in copper to make it weigh heavier. It can be had from platinum works for the trouble of hauling it away. The halogens are very rare. We use them only as very unusual reagents. A very small percentage of them is a requisite to life processes, but very, very little. They occur to a small extent in sea water."

	"Your world is vastly different from ours," said Arcot. He related to Tonlos the different metals of the earth, the non-metals, and their occurrence. But try as he would, he could not place the metal Tonlos had given I him.

-

	AT, last Morey was brought in. He was looking very tired, and very, serious. He, also, was suffering from a headache, just as Arcot had. Arcot told him of his discoveries and of the metals of Turo, wondering why it was that the two planets, both members of the same sun, should be so different.

	"I think I know," said Morey slowly, "and the more I think it over, the more firmly convinced I am that I know the metal you can't place.

	"We have all seen pictures of the sun taken by different colored lights. If hydrogen light is used and all others are shut out, we see a picture of the hydrogen on the sun. If calcium light is used, a corresponding result is obtained.

	"This work was started back as far as 1900 or so, and in that time lots of elements have been mapped, and we have watched the elements change their locations. In this way we are getting a map of the sun showing the deposits of the different elements. We have seen hydrogen, oxygen, silicon and others, and as the sun aged, the elements must have been mixed up more and more thoroughly. Yet we have seen the vast deposits. Some of those deposits are so vast that they could easily be the source of an entire world! I wonder if it is not possible that earth was thrown off from some deposit rich in iron, aluminum and calcium, and poor in gold, radium and those other metals—and particularly poor in one element. There are some gaps in the periodic table—you know them—there is a counterpart to manganese, a heavier metal still to be found. We have located in the sun the spectrum of an element we have named coronium—and I think that you have a specimen of coronium in your hand there! Venus came from a coronium impregnated region!

	"Most of the meteorites that fall to earth have a large iron content—but remember that earth was thrown out of the sun violently, whenever it was thrown out, and with it must have come a lot of loose material that may have been thrown out and shot out into space to form long elliptic orbits that bring them near the sun once in a billion years. These pieces are really part of the earth that fall back to it as it advances in its orbit—naturally they will be high in iron—like the earth—and scientists observing them say, 'Ha—meteorites are full of iron—all planets must be full of iron!' But their logic is being unbalanced by errors, hidden by Nature. My idea sounds possible—and it does explain the facts of Venus."

	"Most of the meteorites that strike this planet are high in iron, too—but the sun is in general, too. However, we get many meteorites high in coronium, as you call it," said Tonlos.

	The discussion was soon ended, for already the air outside had passed to a murky twilight. It was nearing night now, and the Terrestrians were led quickly down to the elevator, which dropped them rapidly to the ground. There was still a large crowd about the Solarite, but the way was at once cleared for them, and a peculiar, sensation struck both the Terrestrians very forcibly. It seemed that everyone in the crowd was wishing them the greatest success—the best of things in every wish.

	"The ultimate in applause! Morey, I'll swear we just received a silent cheer!" laughed Arcot, as they stood inside the airlock of the ship once more. It seemed home to them now! In a moment they had taken off the annoying ventilating suits and stepped once more into the room where Wade and Fuller awaited them.

	"Say—what were you fellows doing. We were actually getting ready to do some inquiring about your health!" said Wade, still a bit worried.

	"I know we were gone a long time—but when you hear the reason, you won't wonder so much! See if you can raise earth on the radio yet, Morey, will you, while I tell these fellows what happened? If you succeed, tell them to call in Dad and your father, and to have a couple of phono-type machines on the job. We will want a record of what I have to send. Say that we will call back in an hour." Then, while Morey was busy down in the power room sending the signals out across the forty million miles of space that separated them, Arcot told Wade and Fuller the news that he had learned. Not only was half of Venus in danger—but earth itself was for the first time in millions of centuries in danger of attack!

	Morey finally succeeded in getting his message through, and returned to say that they would be waiting in one hour. He had had to wait eight minutes after sending his message to get any answer, however, due to the slowness of radio waves.

	"Fuller—you're the chef—if you do your job, Wade and I will start on this piece of coronium here and see what there is to learn," said Arcot. "We can be ready by the end of the hour."

	At supper table Wade and Arcot were exclaiming over the curious constants they had discovered for coronium. It was not attacked by any acid except boiling selenic acid, since it formed a tremendous number of insoluble salts. Even the nitrate violated the long-held rule that "all nitrates are soluble"—it wouldn't dissolve. Yet it was chemically more active than gold.

	But its physical constants were the most surprising. It melted at 2800 centigrade, a very high melting point indeed. Very few metals are solid at that temperature. But the tensile strength test made with a standard bar they had finally turned out by means of a carbaloy tool, the second hardest thing known, tungsten carbide and cobalt, gave a reading of over a million, three hundred thousand pounds per square inch! It was far stronger than iron—stronger than tungsten, the strongest metal heretofore known. It was twice as strong as the earth's strongest metal!

	"No wonder they can make a plane like that when they have such a metal to work with," said Fuller. The designing engineer had visions of a machine after his own heart—a machine where half the weight wasn't employed in holding it together.

	It was a little later that they got communication through to earth, and the men went to the power room. The televisor was blinking, struggling to form a clear image despite the handicap of forty million miles of space. In a moment it had cleared, though, and they saw the face of Dr. Arcot. He showed plainly that he was worried about the startling news that had reached him already, sketchy though it was. Rapidly his son outlined to him the full extent of their discoveries, and the things that earth would have to meet with.

	"Dad, these Kaxorians have planes capable of far more than a thousand miles an hour in the air. For some reason the apparatus they use to propel them in space is inoperative in air, but their giant propellers will drive them forward faster than any plane earth ever saw. You must start at once on a fleet of these molecular motion planes—and a lot of the gas Wade developed—you know how to make it—the animation suspending gas. It will be useful—and I will try to develop some new weapon here. If either of us makes any progress along new lines—we will talk each night—I must stop now—some Lanorian scientists are coming."

-

	WHILE the Solarite rested, there had been a large crowd of people gathered around it, waiting a glimpse of the Terrestrians—for now the news had spread that this car had come from earth. Now, however, a group of men was advancing toward the car, they were clothed in great furs, heavy coats that seemed warm enough to wear in the arctic regions!

	"Why—Arcot—what's the idea of the arctic regalia?" asked Fuller in surprise.

	"Think a moment—they are going to visit a place whose temperature is seventy degrees colder than their room temperature. Into the bargain, Venus never has any seasonal change of temperature, and the heavy bank of clouds that eternally cover the planet keep the temperature as constant as a thermocouple arrangement could. The slight change there is from day to night is only appreciable by the nightly rains see the crowd is beginning to break up now—it is night already, and there is a heavy dew settling now, soon it will be rain, and the great amount of moisture in the air will supply enough heat, in condensing, to prevent a temperature drop of more than two or three degrees.

	"These men are not used to changes in temperature as we are and hence they must protect themselves far more fully. Even in exploring their arctic, I imagine they never find frozen water—the heat held in by the clouds prevents that"

	Three figures now entered the air-lock of the Solarite, and muffled in their furs as they were, large under any conditions, they had to come through one at a time.

	Much that Arcot showed them was totally new to them. Much he could not explain to them at all, for their physics had not yet reached that stage.

	But there was one thing he could show them, and he did. There were no samples of the liquids he wanted, but their chemistry was developed to a point that permitted the communication of the necessary data and Arcot told them the formula of Wade's gas. This gas was somewhat radioactive in character due to the incorporation in the molecule of an atom,of the radioactive thorium, but partly due to this, it had the wonderful property of suspending animation for several months, and of permitting full recovery on the administration of a dose of potassium iodide. There was a second equally striking peculiarity—it could penetrate any material. It had been known for many centuries that carbon monoxide was able to penetrate a sheet of steel when the steel was at a dull red heat but Wade had found the reason for this property, and developed it to a far greater degree, till the gas he made was able to penetrate any material at ordinary temperatures. Combined with its anesthetic properties, it had obvious advantages as a gas for rendering the opposing forces defenseless.

	Since it was able to penetrate all substances, there were no means of storing it—like the famous universal solvent—"what'cha gonna keep it in?" The answer was that two liquids were made to react spontaneously and produce the gas, which was then projected as any other to the spot where needed.

	Arcot asked now that the Venerian chemists make him a supply of these two liquids. He felt he would be much better equipped to attack the enemy if he could but capture one of their flying forts. It seemed a strange task! Capturing so huge a machine with only the tiny Solarite—'but Arcot felt sure he would be able to do it, if he but had a supply of that gas.

	There was one difficulty—it required a considerable portion of chlorine gas to make it—though the chlorine itself was not part of the product; one step in the synthesis required it. Since chlorine was rare on Venus, the men were forced to sacrifice most of their salt supply, but this chlorine so generated could be used over and over again. Realizing the importance of the gas, the Lanorians agreed to synthesize it.

	It was quite late when the Venerians had left, to go again into the hot drizzle of the rain. The rain was, as Arcot found, really scaldingly hot, but to these Venerians it appeared as a cold drizzle. But it was as natural to them as was the air, the ocean or the sunshine. They merely accepted it as one of the things that were.

	The building before which the Solarite now rested was the capital building of Lanor. There were here the government laboratories and the National College. With the help of these two institutions it was hoped that the work of making the necessary materials would progress rapidly.

	Shortly after the Venerians left, the Terrestrians turned in for the night, leaving a telephone connection with the guard outside. In view of the tremendous results the Solarite would bring into the balance of this war, Lanor had had a special guard established about it

	The dull light of the Venerian day was filtering in through the windows the next morning when the Terrestrians awoke. It was eight o'clock, New York time, but Sonor was working on a twenty-three hour day. It happened that Sonor and New York had been in opposition at midnight two nights ago, which meant that it was now ten o'clock Sonorian time. The result was that Arcot and Morey, the first up, found the Venerian world in full swing of its morning business. Quickly they called the others, and while Fuller was preparing the morning meal, Arcot left the car to speak to the officer in charge of the guard about the ship.

	"We need some pure water—water free of copper salts. I think it would be best if you can get me some water that has been distilled. That is, for drinking. Also we need about two tons of water of any kind—the ship's tanks need recharging. I would like about a ton of the drinking water." Arcot had to translate the Terrestrian measures into the corresponding Venerian terms, of course, but still the officer seemed puzzled. Such a large amount of water would mean a real problem in getting it here. Could the Solarite be moved to some mere accessible place?

	Arcot agreed to have it moved to a spot just outside the city, where the water could be procured directly from a small stream. The drinking water would be ready when he returned to the city.

	The Solarite was moved to the shore of the little river and the electrolysis apparatus was set up beside it. During the previous day, and ever since they had landed on Venus, all their power had been coming from the storage cells, but now that the electrolysis apparatus was to establish such a heavy and constant drain, Arcot started the generator, to both charge the cells, and to do the work needed.

-

	THROUGHOUT the day there was the steady hum of the generator in its room, and the throb-throb-throb of the oxygen pump, as the gas was pumped into the huge tanks. The apparatus they were using produced the gas very rapidly, but it was near nightfall before the huge tanks had again been filled. Even then there was a bit more room for the atomic hydrogen that was simultaneously formed, although twice as much hydrogen as oxygen was produced. Then the Solarite rose again and shot swiftly toward the distant city.

	There was a soft red glow now, for even through the miles of clouds the intense sun was able to give some direct rays, and all the city was lighted with that warm glow. The floodlights had not yet been turned on, but the great buildings looming high in the ruddy light were wonderfully impressive, the effect being heightened by the cooperation shown, for there were no single spires, only a single mass that grew from the ground to tower high in the air, like some man-made mountain.

	The Venerian buildings had a slightly different type of architecture, in-that, though the vertical lines were always accentuated to lead the eye upward, to increase the effect of height, the horizontal lines were even further reduced by making them all curves. There were no angles, the entire outside was curving. The effect was much more pleasing than the sharp angles of Terrestrial buildings.

	Back at the Capital the Solarite again settled into the broad avenue that had been cut off now, and allotted to it as its resting place. Tonlos me}; them shortly after they had settled into place, and with him were five men, each carrying two large bottles.

	"Ah-co," as Tonlos pronounced the Terrestrian name, "we have not been able to make very much of the materials needed for your gas, but before we made any very great amount, we tried it out on a Venerian animal, whose blood structure is the same as ours, and found it had the same effect, but that in our case the iodide of potassium is not as effective in awakening the victim as is the 'sorlon'. I do not know whether you have tried that on Terrestrial animals or not. Luckily sorlus is the most plentiful of the halogen group; we have far more of it than of chlorine, bromine or iodine."

	"Sorlus? I do not know of it—it must be one of the other elements that we do not have on earth. What are its properties?"

	"It, too, is much like iodine, but is heavier. It is a black solid melting at 570 degrees; it is a metallic looking element, will conduct electricity somewhat, oxidizes in air to form an acidic oxide, and forms strong oxygen adds. It is far less active than iodine, except toward oxygen. It is very slightly soluble in water. It does not react readily with hydrogen, and the acid where formed is not as strong as HI."

	"I have seen so many new things here, I wonder if it may not be the element that precedes niton. Is it heavier than that?"

	"No," replied Tonlos; "it is just lighter than that element you call niton. I think you have none of it"

	"Then it must be the next member of the halogen series, Morey. I'll bet they have a number of those heavier elements," said Arcot.

	Later work identified sorlus as number 85, and morlus as number 93! There are but 92 elements possible on the table, as earth knows them, but Venus has several very rare, and some highly radio-active elements, that earth does not have. Their table stops at a more logical place than does our Terrestrial table. They know of a heavy inert gas, number 104.

	The gas was loaded aboard the Solarite that evening, and when Wade saw the quantity that they had said was "rather disappointingly small" he laughed heartily.

	"Small! They don't know what that gas will do! There is enough stuff there to gas this whole city out of business. Why, with that we can bring down any ship! Tell them to go on though, we can use it on the other ships."

	Again that night they spoke with earth, and Morey, Senior, told them that work was already under way for a hundred small ships. They were using all their own ships already, while the Government got ready to act on the idea of danger. It was a little hard to convince them that someone on Venus was getting ready to send a force down to earth to destroy them. However, the ships now under construction would be ready in three weeks. They would be unable to go into space, but they would be very fast, and capable of carrying large tanks of the gas-producing chemicals.

	It was near midnight, Venerian time, when they turned in. They must start the next day for the Kaxorian construction camp. They had learned from Tonlos that day that there were but five of the giant planes ready to work now, but there were fifteen more under construction to make up the fleet of twenty that was to attack earth. These fifteen others would be ready in one week—or less. When these were ready, the Solarite would stand small chance. They must capture one of the giants and learn its secret, and then, if possible fight them.

	Their opportunity came sooner than they had hoped for—or wanted. It was about three o'clock in the morning when the telephone warning hummed loudly through the ship. Arcot answered.

	Far to the east and south of them the line of scouts that hung in their little planes over all the borders of Lanor had been broken. Instantaneously almost, out of the dark, its lights obscured, the mighty machine had come, striking the tiny scout plane head on, destroying it utterly before the scout had a chance to turn from the path of the titanic ship. But before the plane was destroyed the pilot had had a chance to light a magnesium flare, a blindingly brilliant flare that floated down on a parachute, and in the blaze of white light it gave off, the other scouts at a few miles distance, had seen the mighty bulk of the Kaxorian plane. At once they had dropped to the ground, and then, by telephone lines, they had sent their message to far off Sonor. The plane they had seen had no doubt been heading for the capital!

	At once Arcot turned to the others and cried to them to get up at once. There was some real action to be had now! All day they had been doing so little toward the thing they knew must come, the battle for two worlds, they had wanted action, but they had no weapons except their invisibility and the atomic hydrogen. It would not sink a plane. It would only break open its armor. If it did sink them, they could learn nothing from it, for it would be the very things they wanted to learn about that they would have destroyed.

-

	ARCOT lifted the Solarite at once high into the air, and started toward the point on the border, where the plane had been seen crossing. In a short time Wade relieved him at the controls while he dressed.

	They had been flying on in silence for about an hour, when suddenly Wade made out in the distance the great bulk of the plane, against the dull grey of the clouds, a mile or so above them. It seemed some monstrous black bat flying there against the sky, but down to the sensitive microphone on the side of the Solarite came the drone of the hundred mighty propellers as the great plane forged swiftly along.

	Just how rapidly these giants moved, Arcot had not appreciated until he attempted to overtake this one. It was going over a mile a second now! The ship had but to go its own length in about five-eighths of a second to do this. It was a lower speed to this monster; the individual molecules of air meant less to it. It made greater speeds, both by streamlining and through sheer power, such as nothing else could approximate.

	The Solarite was hovering high above the dark ship now, the roar of the terrific air blast from the propellers below came up to them here as a mighty wave of sound that made their ship tremble! The hundred gigantic propellers roaring below, however, would distribute their gas perfectly.

	"I am going into invisibility. Look out!" There was a click as the switch shut, and the Solarite was as transparent as the air about it. Now Arcot dived the ship swiftly in front of the mighty colossus, then pulled a small switch shut. There was a low hiss from the power room—barely detectable despite the vacuum that shut them off from the roar of the plane for the whole ship trembled. The microphone had long since been disconnected. Out of the gas vent now a thin stream of a purplish gas was streaming, becoming visible as it left the influence of the invisibility apparatus, but only to those who knew where to look for it. Those men in that mighty plane could not see it—it was invisible to them as their machine bore down into the little cloud of gas—but an instant later the gigantic plane was wobbling in its course—it seemed uncontrolled! There was a sudden swerve that ended in a nose dive, straight to Venus seven miles below all the great propellers roaring, pulling it on. The pilot had fallen over his controls.

	That the ship should crash nose on into the ground below was not at all Arcot's plan, and he was greatly relieved as the plane, an instant later, when the rapid fall had removed the weight of the man on the controls, and permitted the plane to balance itself, coming again under normal conditions, flattened its dive, and started to climb up, its titanic mass rapidly absorbing its kinetic energy. Down from its seven-mile height it glided, controlling itself perfectly as Arcot released the last of the first four bottles of the liquid gas makers, putting to sleep the last man on the ship below.

	In a long glide that carried it over many miles, the great ship came down. It had sunk far, and gone smoothly, but now there loomed ahead of it a range of low hills! It would certainly crash into the rocky cliffs ahead—nearer and nearer it came—it might skim above those low hills at that—but just then there was a little dip, and head on, at nearly two thousand miles an hour, the titanic machine crashed into the rocks. Arcot had snapped the loud speaker into the circuit once more, and now as they looked at the sudden crash below, there came slowly to them the mighty waves of sound!

	The giant plane had hit the top, twenty feet or so of a nearly perpendicular cliff. There was a terrific crash that was felt by seismographs in Sonor nearly two thousand miles away! The mighty armored hull plowed its way into the rocks like some gigantic meteor, the hundreds of thousands of tons crushing the rocky precipice like tissue paper, grinding the rocks to powder, and shaking the entire hill. The cliff seemed to buckle and crack. As the terrific momentum of the huge plane struck it, it was torn and twisted. In an instant the plane had been brought to rest, but it had plowed through twenty feet of rock for nearly an eighth of a mile. For an instant it hung there, perched perilously in the air, its tail hanging out over the little valley below, then slowly, majestically it sank, to strike with a reverberating crash that broke the heavy armor plate like a match-box! For an instant longer the great motors continued working, the roar of the propellers like some throbbing background to the rending crashes as the titanic wreck came to rest. Suddenly there was a series of crashing explosions, and one after the other, the entire series of motors in the left wing blew up with awful force. There was a flash of light that could be termed a blast; the terrific brilliance seemed to blind the Terrestrians watching this scene of awful desolation; then there came to the microphone such waves of sound as it could not record; the Solarite seemed to jump with each successive explosion. There was no dust at first, only they could see a fused mass of metal that they knew had been the wing, broken, rent, smashed where each of the fifty motors had been. The rocks beneath seemed powdered now, as a great cloud of dust rose. Still the motors on the other side of the ship were roaring and the giant propellers turned. It was these that blew the dust away. The Terrestrians stared in unbounded amazement as they saw playing from the gaping, broken wing a mighty beam of light of such dazzling intensity that Arcot at once restored them to visibility that they might shut it out. There was a terrific hissing, crackling roar. The plane seemed to wobble as it lay there, recoiling from that stream of flaming gas, it seemed. Where it touched the cliff there was intense incandescence that made the rock glow white hot, and from it rose clouds of vapor—BOILING ROCKS! For five minutes longer this terrific spectacle lasted, while Arcot withdrew the Solarite from the plane. The fifty motors of the remaining wing seemed slowing down now—then suddenly there was such a crash and towering flash of light as no human being had ever seen before! Up—up into the very clouds it shot its mighty flame, a blazing column of light that seemed to reach out into space. The Solarite was hurled back end over end, tumbling, falling. Even the heavy gyroscopes could not hold it for an instant, but quickly the straining hum of the motors brought the Solarite to rest in air that whirled and whined about them. They were over twenty miles from the scene of the explosion, but even at that distance they could see the glow of the incandescent rock. Slowly, cautiously they maneuvered the Solarite back to the spot, and looked down on a sea of seething fluid rock!

	"Lord—what power that thing carries! No wonder they can support that gigantic thing in the air! How can they keep such awful power under control? There is no trace of that giant plane! What titanic forces they use! We can never bring down a ship that way and examine it!" Morey was looking at the glowing rocks in awe-struck wonder. Was it possible that what they had seen was true—it was no dream? Such forces as they had seen were powers to make a world with, to fling out of space a blazing sun—these were no such forces as man should use!

	Slowly Arcot was drawing away—off into the night—into the kindly darkness once more.

	"I wonder what those forces were—they are greater than any man has ever before seen! An entire hill was fused to molten, incandescent rock, let alone the tons and tons of metal that made up that ship.

	"And such awful forces as these are to be released on our earth!" Slowly Arcot continued his way. For many seconds they sat silent as the panorama of hills glided by at a slow two-hundred miles an hour. "We must capture a ship. We will try again—we will either destroy, or capture it—-and either is to our advantage!"

-

	FOR miles they continued thus leisurely on across the vast plain. There were no great mountains on Venus, for Venus had known no such violent upheaval as the making of a moon. They seemed lost in thought, each on his own line. At last Wade stood up, and walked slowly back to the power room. Suddenly the men in the control room heard his call: "Arcot—quick—the microphone—and rise a mile!" The Solarite gave a violent lurch as it shot vertically up a mile at tremendous acceleration. Arcot reached quickly over and snapped the switch of the microphone—suddenly there came to their ears the familiar roaring drone of a hundred mighty propellers. No slightest hum of motor, only the vast whining roar of the mighty propellers.

	"Another one! They must have been following the first by a few minutes. We will try to get this one!" Arcot was working swiftly at his switches. "Wade-strap yourself in the seat there—don't take the time to come up here."

	The Solarite dived suddenly in front of the great plane, and as the nose dipped, it was invisible. They were rushing along before a mighty giant again, they were drowned in a titanic wave of rushing sound—then again came the little hiss of the gas. Now there were no hills in sight, as far as the eye could reach. In the dim light that seemed always to filter through these grey clouds they could see many miles.

	It seemed several minutes before there was any effect; these men of earth were waiting for that great ship to move, to wobble from its course. Suddenly Arcot gave a cry of surprise, startled amazement was written all over his face, as his companions turned in wonderment to see that he was partially visible! The Solarite, too, was a misty ghost car about them; they were becoming visible! Then in an instant it was gone—and they saw that the huge black bulk behind them was wavering, turning; the motors had suddenly died till the thunderous roar of the propellers was a whistling whine; the ship was losing speed! It dipped, and shot down a bit—gained speed, then step by step it glided down—down—down to the surface below. The great engines were idling now, and the great machine was running more and more slowly—Its landing speed was surprisingly low—slower and slower it went—they were near the ground now—would this ship, too, crash? Would it, too, be lost in a terrific holocaust that left the very rocks it crashed in a molten, boiling cauldron? It was within a half mile of the ground now—then it dipped once more, and Arcot breathed his relief as it made a perfect landing, the long series of rollers on the base of the gigantic hull seemed to spring enough to absorb the shock of that titanic ship and the hundreds of thousands of tons of metal as they fell through a distance of ten feet. The mighty ship rolled smoothly along the ground—there were small streams in the way—a tree or two. But these were obstacles unnoticed by the gargantuan machine.

	Its mighty propellers still idling slowly, the huge plane rolled to a standstill.

	In an instant the Solarite had landed beside it, it seemed lost in the vast shadows of the mighty metal walls that loomed up beside it.

	Arcot had left a; small radio set with Tonlos in Sonor before he started on this trip, and had given him directions on how to locate the Solarite by its means. Now he sent a message to him, telling that the plane had been brought down, asking that a squadron of planes be sent at once.

	Wade and Arcot were elected to make the first inspection of the Kaxorian plane, and clad in their cooling suits, they stepped from the Solarite, each carrying, in case of emergencies, a small hand torch, burning atomic hydrogen, capable of melting its way through even the heavy armor of the great plane.

	As they stood beside it, looking up at the gigantic walls of metal that rose sheer beside them, hundreds of feet straight up, it seemed impossible that this mighty thing could fly, that it could be propelled through the air. In awed silence they gazed at its mighty bulk.

	Then, like invisible pygmies beside some mighty prehistoric monster, they made their way along its side, seeking a door.

	"Arcot—this is senseless—we cannot do this—the machine is so vast that it will take us half an hour of steady walking to circumnavigate it—we must go in the Solarite to find the entrance!" Wade gestured hopelessly at the vast hull.

	It was well they followed Wade's plan, for the only entrance was from the top. There, on the back of the giant, the Solarite landed—its thousands of tons affecting the Titanic machine not in the least. There was a trap-door on the back of the plane that led down inside. However, the apparatus for opening this was all on the inside, so it was necessary to burn a hole in the door before they could enter.

	What a sight there was for these men of earth. The low rumble of the idling engines was barely audible as they descended the long ladder to the interior of the gigantic hull.

	It suggested no flying machine as they entered here; more it resembled some great power house, where the energies of half a nation were generated. They entered directly into a mighty hall that extended for a quarter of a mile back through the great hull, and completely across the fuselage. To the extreme nose it ran, and throughout there were scattered little globes that gave off an intense white light. The great room was lighted from end to end. There were translucent bull's-eyes obscuring the few windows.

	All about, among the machine, lay men, dead they seemed, though the two Terrestrians knew that they could be restored to life readily. The great machines they had been tending were humming softly, almost in-audibly. There were two long rows of them. Down all the great hall they were, mighty generators they seemed, generators that loomed twenty feet high, but from their peaks ran great tubes two feet thick of solid fused quartz. Then from these led other rods of fused quartz, rods that led down through the floor, but these were more slender; scarcely over eight inches thick.

	The huge generator-like machines were disc-shaped, except that on one side of each there was a little cylinder at the center, like a bearing. From these, too, there ran a quartz rod, down through the floor. The machines on the further row were in some way different; those in the front half of the row had the tubes leading down to the floor below, but they had no tube leading to the roof above; instead, there were many slender rods leading over to a gigantic switchboard that stretched along all one side of the great room. Only the front half had instruments on, and few of these instruments had controls. But everywhere were the great quartz rods, leading about like some complicated water system. They were usually painted black though the main rods leading from the roof above were clear as the crystal they were made of.

	The Terrestrians looked at these gigantic machines in hushed awe—they seemed impossibly huge—it was inconceivable that all this was but the power room of an airplane!

-

	DOWN to the next floor they went. Down a long staircase, down, down, down many feet, for now they reached the main room, it seemed. It was as long as the one above, and higher, yet all that vast space was taken by one single, titanic coil that stretched from wall to wall! Into it, and from it there led two gigantic columns of fused quartz. That these were rods, such as those smaller ones above was obvious, but each was over eight feet thick!

	Short they were, for they led from one mighty generator such as they had seen above, but magnified on a scale inconceivable! At the end of it, its driving power, its motor, was a great cylindrical case, into which led a single quartz bar ten inches thick, and this bar seemed alive now with living, glowing fires, that changed and maneuvered and died out over all its surface and through all its volume. The motor was but five feet in diameter and a scant seven feet long, yet obviously it was driving the great machine, for there came from it a constant low hum, a deep pitched song of awful power. And the huge quartz rod that led from the titanic coil-cylinder was alive with the same glowing fires that played through the motor rod. From one side of the generator, though, there ran two things that were familiar, copper bus bars. But even these were THREE FEET THICK!

	The scores of quartz tubes that came down from the floor above joined, coalesced, and ran down to the great generator machine, and into it. From it ran a similar quartz bar up to that front battery of machines that had been working upstairs, and these were alive with the strange force that lived.

	Down again they went to another floor. Here were other quartz tubes, but these led down still further, for this floor contained individual sleeping bunks, and most of them were unoccupied, unready for occupancy, though some were made up.

	Down another level; again the bunks, the little individual rooms.

	At last they reached the bottom level, and here the great quartz tubes terminated in a hundred smaller ones, and each of these led into some strange mechanism. But there were sighting devices on it, and there were ports that men might see down. It was evidently designed as the bombing room.

	Now the Terrestrians walked through the vast city of the dead to the front of the machine, and passed sleeping officers, and on the third level they came at last to the control room. Here were switchboards, control panels, and dozens of officers, sleeping now, beside the instruments they had been tending. There was a sudden thudding that made the earth men jump, as an automatic relay adjusted some mechanism.

	There was one man stationed apart, at the very bow he sat, protected behind eight-inch coronium plates, .but in them were set masses of fused quartz that were nearly as strong as the metal itself. These gave him a view in every direction except directly behind him. Obviously, here was the pilot.

	To the top level they went again, and now they entered the long passages that led out into the titanic wings. Throughout, the ship was brightly lighted. Now they came to a small room, another bunk room. There were great numbers of these down both the sides of the long corridor, and along the two parallel corridors down the wing, but in the fourth corridor near the back edge of the wing, there were bunk rooms on one side, and on the other were bombing posts.

	As they walked down the corridor further, however, along this first one, they soon came to a small room, whence came the low hum of one of the motors. Entering, they found the crew sleeping, and the motor idling.

	"Good Lord! Look at that motor! Arcot—it's no bigger than the trunk of a man's body! Yet it can spin that huge propeller at a speed that will send this ship hurtling along at a mile a second! Just think of the awful power of that big thing driving the generator! And it had a ten-inch bar of quartz leading into it! What powers did those eight-foot quartz rods carry? No wonder that machine back there blew up so terrifically!" Wade was sobered by the thought of the titanic energies that were represented by these giant rods. Slowly they proceeded down the long hall. At each of the fifty engine mountings they found the same conditions. At the end of the hall there was a stairway that led one level higher, into the upper wing. Here they found long rows of the bombing posts and the corresponding quartz rods.

	They returned finally to the control room. Here Arcot spent a long time looking over the many instruments, the controls, and the piloting apparatus.

	"Wade, I think I can see how this is done. I am going to stop those engines, then start them, then accelerate them till the ship rolls a bit!" Arcot stepped quickly over to the pilot's seat, lifted the sleeping pilot out quickly, and settled in his place.

	"Now you go over to that board there—that one—and when I ask you to, please turn on that control—no the one below—yes—turn it on about one notch at a time."

	"All right Arcot—just as you say—but when I think of the powers you are playing with—well it isn't healthy to make a mistake!" laughed Wade. He was nervous, perhaps, but the excitement of the adventure, of controlling the awful forces there in the ship behind him—they were too much of an inducement!

	"I'm going to stop the motors now." All the time they had been on board, there had been the low whine of the motors barely audible. Now suddenly, it was gone, and the plane was still as death!

	"I did it without blowing the ship up after all—now one more—we are going to try turning the power on!"

-

	SUDDENLY there was a throaty hum; then quickly it became the low whine; then, as Arcot turned on the throttle before him, he heard the tens of thousands of horsepower spring into life—and suddenly the whine was a low roar—the mighty propellers out there had become a blur—then with majestic slowness the huge machine moved off across the field!

	The motors were shut off now as they made their way again up through the ship, up through the room of the titanic cylinder coil, and then into the power room. Now the machines were quiet, for the motors were no longer working.

	"Arcot, you didn't shut off the biggest machine of all down there. How come?"

	"I couldn't, Wade. It has no shut-off control, and if it did have, I wouldn't use it. I will tell you why when we get back to the Solarite."

	At last they were out of the mighty machine, walking once more across the broad metal roof. Here and there they now saw the ends of those quartz tubes. Once more they were entering the Solarite, through the air lock, and taking off the cumbersome heat suits.

	As quickly as possible Arcot outlined to the two who had stayed with the Solarite the things they had seen, and the layout of the titanic ship.

	"I think I can understand the secret of all that power, and it is not so different from the Solarite, at that. It, too, draws its power from the sun, though in a different way, and it stores it within itself, which the Solarite does not try to do.

	"It has been known since the days of Einstein that mass is a representation of energy. It is a measure of energy, just as weight is a measure of mass. The amount of mass a body has depends solely on the amount of energy it contains. Thus, to say that a thing has a mass of one gram is equivalent to saying it contains 900000000000000000 (9x1020) ergs of energy. Similarly, the converse is true, and any energy, if it be that many ergs of energy, it has a mass of one gram no matter what form it has. That is the reason why a mass grows greater when it goes faster; it is acquiring kinetic energy, and hence more mass—the mass of the kinetic energy.

	"Light is energy, and light, therefore, has mass. That is obvious when you stop to think of it. It exerts pressure, the impact of its moving units of energy—photons. We have electrons and protons of matter, and photons of light. Now we know that the mass of protons and electrons will attract other protons and electrons, and hold them near—as in a stone, or in a solar system. Now the new thing is that photons will attract each other in the same way—by the law of mass gravitation they will attract each other ever more and more powerfully, the closer they get. The Kaxorians have developed a method of getting them so close together, that they will, for a while at least, hold themselves there, and with a little 'pressure' they will stay there indefinitely.

	"Wade, in that huge coil and cylinder we found there we saw the main power storage tanks. That was full of gaseous light-energy held together by its own attraction, plus a little help of the generator."

	"A little help? Quite a little! I'll bet that thing has a million horsepower in its motor!"

	"Yes—but I'll bet they have nearly fifty pounds of light condensed there—so why worry about a little thing like a million horsepower? They have plenty more where that comes from.

	"I think they go up above the clouds in some way and collect the sun's energy. Remember that Venus gets twice as much as the earth. They focus it on those tubes on the roof there, and they, like all quartz tubes, conduct the light down into the condensers where it is first collected. Then it is led down to the big condenser downstairs, where the final power is added, and the condensed light is stored.

	"Quartz conducts light just as copper conducts electricity—those are bus-bars we saw running around there.

	"The bombs we have been meeting recently are, of course, little knots of this light energy thrown out by that projector mechanism we saw. When they hit anything, the object absorbs their energy—and is very promptly volatilized by the heat of the absorption.

	"Do you remember that column of hissing radiance we saw shooting out from the wrecked plane just before it blew up? That was the motor connection, broken, and shooting out its energy freely. That would ordinarily have supplied all fifty motors at about full speed. Naturally, when it got loose, it was rather violent.

	"The main generator had been damaged, no doubt, so it stopped working, and the gravitational attraction of the photons wasn't enough, without its influence to hold them bound too long. All those floods of energy were released instantaneously, of course.

	"Look—there come the Lanorians now. I want to go back to Sonor and think over this problem. Perhaps we can find something that will release all that energy—though honestly, I doubt it."

	Arcot seemed depressed, overawed perhaps, by the sheer magnitude, the titanic brute force that lay bound up. It seemed inconceivable that the little Solarite could in any way be of avail against the gargantuan machine. The Lanorian planes were landing, on the wings, the fuselage, the ground beneath all about the gigantic machine. Arcot stood gazing moodily through the window, looking at the mighty bulk that rose black and austere beside him, a mighty giant, stricken now, but only sleeping; in its vast hulk lay such energies as man had never before controlled; within it he knew there were locked the titanic powers of the sun itself. What could the Solarite do against it?

	"Oh, I forgot to mention almost—in the heat of the fight back there it went almost unnoticed." Arcot was talking slowly, dejectedly. "Our only remaining weapon—except the gas, is useless now. Do you remember how the ship seemed to lose its invisibility for an instant? I learned why when we investigated the great ship. Those men are physicists of the highest order. I must acknowledge that we must realize the terrible forces, both physical and mental that we are to meet. They have solved the secret of our invisibility, and now they can neutralize it. They know that we will no longer be able to use that. They began using it too late that time, but they had located the radio-produced interference, due to the ship's invisibility apparatus, and they were sending a beam of interfering radio energy at us. We are invisible only by reason of the vibration of the molecules in response to the radio impressed oscillations. The molecules vibrate in tune, at terrific frequency, and the light can pass perfectly. What will happen, however, if some one locates the source of the radio waves by means of a standard radio directional receiver? It will be a simple process to send a beam of radio waves along that same direction—and touch our invisible car with it. The two radio waves impressed on the car now will be out of step and the interference will instantly reveal the car. The huge ship there can get vastly more energy into their apparatus than we can get in ours and naturally they can make us visible. They will do so—and we can no longer attack them either with our atomic hydrogen blast, nor with the gas—it is useless unless we can get close to them, and we can not come within miles of them. Those bombs of theirs are effective at a distance of ten miles—above that they disintegrate automatically.

	"We were protected from them as long as we were transparent, too, for the bombs could pass right through us just as they passed through the air. Only opaque bodies are susceptible."

-

	AGAIN he fell silent, standing morosely at the window—thinking—hoping for an idea that would enable them once more to have hopes of winning.

	"Wait a minute fellows—I'm going out to speak with the Commander-in-Field here. Then we can start back for Sonor—and maybe we had best start back for earth. It looks as though there is little we can do here."

	Briefly he spoke to the young Venerian officer, and told him that the ship could be left there undestroyed if he would open a certain control just before he left. Arcot showed him which one—it would drain out the power of the great storage tank, throwing it harmlessly against the clouds above. The Kaxorians might destroy the machine if they wanted to—Arcot felt that they would not wish to. They would hope, with reason, that they might recapture it! It would be impossible to move that tremendous machine without the power that its "tank" was intended to hold.

	Slowly they were cruising back to Sonor. Arcot was still standing by the window of the ship, thinking.

	Would it be that Venus would fall before the attack of the mighty planes, that they would sweep out across space, to Earth—to—Mars—to other worlds, a terrific cosmic menace? Would the mighty machines soon be circling earth—defenseless—the greatest of the 30-inch rifles would be unable to more than dent that eight inch coronium armor. It was more than equivalent to twenty-four inches of steel. They would be invulnerable; the planes would be unable to get near enough to drop bombs on them. Only the molecular motion machines would even give them a battle! Perhaps these could be armored with twenty-inch steel walls, and driven in a suicidal dive into the great propellers, or at miles a second, into the ship itself! It was the only hope it seemed! But these ships would require long hours, days, even weeks to build, and in that time the Kaxorian fleet would be ready. It would attack earth within six days now! What hope was there?

	In despair Arcot turned and strode quickly down the long hallway of the Solarite. Above him was the smooth, even hum of the sweetly functioning generator, but it could only remind him of the titanic energies he had seen led about that night. The thudding relays in the power room, as Wade maneuvered the ship, seemed some diminutive mockery of the giant relays he had seen in the mighty power room of the Kaxorian plane.

	He sat down in the power room, looking at the stacked apparatus, neatly arranged, as it must be, to get all this apparatus in. this small space. Then at last he began to think more calmly. Slowly he tried to think of the greatest forces man knew of—and there were only two that even occurred to him as great! One was the vast energies he had that very night learned of; the other was the force of the molecules, the force that drove his ship.

	He had had no time to work out the mathematics of the light compression, and it was mathematics that would give results now he knew. There remained only the molecular motion. What could he do with it that he had not done?

	He drew out a small black notebook. In it were symbols, formulas, and page after page of the intricate calculus that had ended finally in the harnessing of this great force that was even now carrying him smoothly along.

	Half an hour later he was still busy—covering page after page with swiftly written formulas. Before him was a great table of multiple integers, the only one like it known to exist in the System, for the multiple calculus was an invention of Arcot's. At last he found the expression he wanted, and carefully he checked his work, excitedly though now, with an expression of eager hope—it seemed logical—it seemed correct—

	"Morey—oh, Morey—if you can come here—I want you to do some Math for me—I have done it—and I want to see if you get the same result independently!" Morey was a more careful mathematician than he, and it was to him Arcot turned for verification of his new discovery.

	Following the general directions Arcot gave him, Morey went through the long series of calculations—and arrived at the same result. Slowly he looked from the brief expression he had ended with—

	It was not the formula that astonished him—it was the physical significance it had.

	"Arcot—do you think we can make it?"

	"I hope so, Morey. If we don't, Lanor is lost beyond a doubt—and probably the earth is, too. Wade—come here a minute, will you—let Fuller take the controls, and tell him to push it. We have to get to work on this."

	Rapidly Arcot explained their calculations—and the proof he had gotten.

	"Our beam of molecular motion-controlling energy directs all molecular motion to go at right angles to it. The mechanism so far has been a field inside a coil really, but if this is right, it means that we can project that field to a considerable distance even in air, a beam of power that will cause all molecules in its path to move at right angles to it, and in the direction we choose, by reversing the power in the projector. That means that no matter how big the thing is, we can tear it to pieces—we will use its own powers, its own energy, to rip it, or crush it. Imagine what would happen if we directed this against the side of a mountain—the entire mass of rock would at once fly off at terrific speed, several miles a second, crashing ahead with terrific power, as the molecules suddenly all moved in the same direction. Nothing in all the Universe could hold together against that! It is a disintegration ray of a sort—a ray that will tear, or crush, for we can either make one half move away from the other—or we can reverse the power, and make one half drive toward the other with all the terrific power of its molecules! It is omnipotent—hmm—but it has one limitation. Will it reach far in the air? In vacuum it should have an infinite range—in the air all the molecules of the air will be affected, and it will cause a terrific blast of icy air, air at temperatures far below zero! This will be even more effective on Venus! But we must start designing the thing at once! Take some of the Immorpho and give me some, and we can let the sleep accumulate till we have more time! Look—we are already in Sonor—we must land, Fuller—right where we were, and then come back here. We are going to need you!"

	The gorgeous display of a Venerian dawn was already starting in the East as the great buildings seemed to rise silently about them. The sky, which had been a dull luminous grey, a grey that rapidly grew brighter and brighter, was now like molten silver, through which the early rays of the intense sun were filtering. Now, the sun rose above the horizon, invisible for clouds. But still it was traceable by the wondrous shell pink that began to suffuse the ten-mile layer of clouds. The tiny droplets were, however, breaking the clear light into a million rainbows, and all about the swiftly deepening pink there were forming concentric circles of blue, of green, orange, and all the colors of the rainbow, repeated time after time—a wondrous halo of glowing color, which only the doubly intense sun could give.

	"It's almost worth missing the sun all day to see their sunrises and sunsets." The men were watching it, despite their need for haste. It was a sight the like of which no Earthman had ever before been privileged to see.

	And then immediately they plunged into the extremely complex calculation of the necessary electrical apparatus to produce the necessary fields. To get the effect they wanted, they must have two separate fields of the director ray, and a third field of a slightly different nature, which would cause the director ray to move in one direction only. It would be disconcerting, to say the least, if the director ray, by some mistake, should work in the opposite direction!

-

	THE work went on even more swiftly than they had hoped, but there was still much to be done on the theoretical end of the job alone when the streets about them began to fill. They noticed that a sizeable crowd was collecting, and shortly after they had finished, after some of those people had stood there over an hour and a half, the crowd had grown to great size.

	"From the looks of that collection, I should say we are about to become the principals in some kind of a celebration that we know nothing about. Well, we are here, and in case they want us» we are ready to come.

	The usual guard that always surrounded the Solarite had been doubled, and was maintaining a fairly large ring about the ship.

	It was shortly after that that they saw one of the high officials of Lanor come down the walk from the governmental building, walking toward the Solarite.

	"Time for us to appear—we may as well all show up for once. I'll tell you what they say afterward, Wade. They have gone to considerable trouble to get up this meeting, so let's oblige by all going out I hate to slow up the work so, but we will make it short."

	The four Terrestrians donned the cooling suits, and stepped outside the ship. It was the first time they had all been outside the ship together!

	"Earthmen, we have gathered here this morning to greet you and thank you for the tremendous service you have done us. Twice you have saved this city from utter destruction. Across the awful void of empty space you have journeyed forty million miles from your planet to visit us, only in time to discover that Venerians were making ready to attack your world. Now you have helped us, saved our cities.

	"There is, of course, no adequate reward for this service; we can in no way repay you, but in a measure we may show our appreciation. We have learned from the greatest psychologist of our nation, Tonlos, that in your world aluminum is plentiful, but gold and platinum are rare, and that morlus is unknown. I have had a small token made for you, and for your friends. It is a little plaque, a disc of morlus, and on it there is a small map of the Solar System. On the reverse side there is a globe of Venus, with a globe of earth beside it, as well as our men could copy the small globe you have given us. The northern hemisphere of each is shown—America, your nation, and Lanor, ours, thus being shown. We want you, and each of your friends, to accept these. They are both tokens of our great indebtedness to you, and symbols of your wonderful flight across infinite space!" The Venerians turned to each of the Terrestrians and presented each with a small metal disc, about three inches in diameter,

	"On behalf of myself and my friends here, two of whom have not had an opportunity to learn your language, I wish to thank you for your great help at the time when we most needed it. You have saved more than a city—you have made it possible to save a world—your earth. But the battle here is but just begun. There are now in the Kaxorian camp eighteen great ships. They have been badly defeated in the three encounters they have had with the Solarite so far. But no longer will they be invulnerable. I have learned that the first plane, the plane which was first attacked by the Solarite is still undergoing repairs. They are patching the great hole that was melted into its side. That will be completed within two days, and then, when they can leave a base guard of two ships, they will attack once more. Furthermore, they will attack with a new weapon. They have destroyed the usefulness of our weapon, invisibility, and in turn, now have it to use against us! We must seek out some new weapon. I hope we are on the right track now, but every moment is precious, and we must get back to the work on it. This address must be short Later, when we have completed the plans, we will have to give plans to your workmen, which you will be able to turn into metal, for we lack the materials. With this help we may succeed, despite our handicap."

	The address was terminated at once. The Lanorians were perhaps disappointed, but they realized the necessity of developing all the powers they could.

	"I wish Terrestrian orators spoke like that,'' remarked Morey as they returned to the ship. "He said all there was to say, but he didn't run miles of speech doing it. He was a very forceful speaker, too!"

	"People who speak briefly and to the point generally are," Arcot said.

	"Perhaps so, but it would be much more intelligible if you would tell me what these plaques they gave us are for. I hope they were gifts—they look expensive!" said Wade smiling at the little piece of blueish metal.

	Arcot told him the gist of the speech as quickly as possible. Then they at once settled back to their work.

	It was nearly noon that day before the theoretical discussion had been reduced to practical terms. They were ready to start work at once, but they had reason to work cheerfully now. Even through air they had found their ray would be able to reach 35 miles! They would be well out of the danger zone while attacking the gigantic planes of Kaxor.

	Morey, Wade and Arcot at once set to work constructing the electrical plant that was to give them the necessary power. It was lucky indeed that they had thought to bring the great mass of spare apparatus! They had more than enough to make all the electrical machinery. The tubes, the coils, the condensers, all were there. The generator would easily supply the power, for the terrific forces that were to destroy the gargantuan ships of the Kaxorians were to be generated in the plane itself. It was to destroy itself; the Solarite was merely the detonator that set it off.

-

	WHILE the Physicists were busy on this, Fuller was designing the mechanical details of the projector. It must be able to turn through a spherical angle of 180 degrees, and was necessarily controlled electrically from the inside. The details of the projector were worked out by six that evening, and the numerous castings and machined pieces that were to be used were to be made in the Venerian machine shops.

	"Wade, come here and help me reduce this, will you?" asked Arcot. He was working with Fuller on the last details of the plans. They were putting in the dimensions that the Lanorians might understand.

	"Their length unit, the 'tsorri,' is exactly 19.2 centimeters. I had a measuring rod here, and compared them—but the system is something like the metric—with this difference. Their entire mathematics is based on the duo-decimal system! Their unit, the tsorn, is divided into twelve parts, each an 'abtsorn,' and similarly multiplied to make an 'ortsorn.' Since their units are on the basis of twelve, they naturally have their lengths in a system based on twelve. Now we have to reduce the centimeters here on Fuller's drawings to equivalents in the tsorn system.

	"Remember that a new system of numbers means a new multiplication table.

	"They have digits that we don't have. They count 'or', 'tel', 'fflur', and so on, but in English they would say, one, two, three, and so on to nine. Then remember that for the next digit they have a single symbol. It happens to be something like this, /, and similarly eleven is ˅. They have twelve now, but they write it—well I can explain it better this way; it corresponds to 10. It means one times twelve. To them, 20 would mean two times twelve, or 24 units to us. Now 100 will mean twelve times twelve or one hundred and forty-four units. The difficulty comes in when we start multiplying. For instance, seven times five is thirty-five to us. They would write it, 7 X 5 =  2˅—that is 'twenty-eleven' or two times twelve plus eleven. Now by the time you introduce such things as twenty-eleven, and eleventy-eleven into your system, the old decimal system looks sort of crippled! The thing we were working on just now was the problem of reducing .2 to the duo-decimal system. Of course, I could say 1/5 in either system, but I want to put it in a duo-decimal. Let's see—five into 1 goes .2 and two to carry—the next now is 4 and then 9 and then 7 and so it's a repeating decimal. The answer is .2497. Now let's go on."

	The problem of working in a new multiplication system was decidedly time-consuming. It was hard to remember that 23 - 18 = 7 and similar peculiar things. But it was done, and at last the work was under way.

	It was night soon, and still the Terrestrians were working. The Venerian workmen had promised to have the apparatus for them by ten o'clock the next morning—or what corresponded to ten o'clock. Their day was divided into twelve equal portions—sensibly, for their numbers were on the duo-decimal system. Wade had been curious to know why they had chosen that basis. It was, of course, as good as any other, and easy to work with, no doubt, when you were accustomed to it—but why twelve? Arcot pointed out that a Venerian has six fingers on each hand, just as a man has five. When man was learning to count, he used his fingers to keep track on, and so, no doubt, had the Venerians done. Naturally they counted by twelves.

	That night Arcot sent to earth the full details of the new ray. If they did not succeed with it, or were in some way destroyed, earth would at least be able to build up the necessary apparatus.

	The time passed quickly, and it was shortly after three o'clock that morning when they finally finished the apparatus and had the controls connected to the control room and the last of the projector directors in place; they were ready, all but the projector, and Morey, Wade and Fuller turned in to get what sleep they could before ten the next morning. But Arcot told them there was something he wished to get, and took another dose of the Immorpho, then stepped out into the steaming rain. It was necessary to wear gloves to prevent the hot rain from scalding him, though the heat suit covered him otherwise. Out into the rain he went, and across to the great government building. Then up quickly to the government chemistry laboratory.

	Wade woke the next morning shortly before ten, and rose quickly, calling the others. Arcot would be back soon, so Fuller started the breakfast.

	It was scarcely ten minutes later when Arcot did return, with half a dozen Venerians following him, each carrying a large metal cylinder in a special cradle. These were attached to the landing runners of the Solarite. The men inside watched with interest as the Venerians wired them on quickly and deftly. They were arranged, however, so that the fusing of one piece of wire would permit the entire thing to drop free, but it was virtually impossible for them to come free otherwise.

	"What was that you were working on there, Arcot?" asked Wade as he entered the ship.

	"It is an idea I want to try out—and I am going to keep it a deep dark secret for a while. I think you will get quite a surprise when you see those bombs in action! They are arranged to be released by turning current into the landing lights. We will have to forego them for the present, but I needed the bombs more than the lights just now. I think they will be successful. The current will melt the wire that holds the main wire supports together. There were no other connectors leading out through the wall of the ship, so I had to use them. The mechanics have finished working on those projector parts you designed, Fuller, and they will be over here in a short time. Here comes the little gang I asked to help us. You can direct them. They will weld the parts in place, and drill the holes for the wires where you say. You know where the best places will be, since you designed the ship, so you take charge of the gang. Hang it all—when they drill into the outer wall, we will lose the vacuum between the two walls, and all that hot air will come in. This place will be roasting in a short time, and we won't be able to walk comfortably for a week! Well, we have some molecular motion coolers.

	"Oh, I wonder if we can't use the generator—oh no, I forgot that we had decided to isolate that from the main room by vacuum wall. Otherwise we could let it use the heat of the rooms. I think we had better charge up the gas tanks and the batteries as soon as this is done. Then tonight we will attack the Kaxorian construction camp. It will be best to attack them before they attack us again. I don't like the news I just got either. There have been no reports from the spies the Lanorians sent over—they are sure to spring some surprise on us soon! We had best get over there!''

-

	SHORTLY later the sound of the drills, then the whistling roar as the air sucked into the vacuum, told the men inside that the work was under way. It soon became uncomfortably hot as, the vacuum destroyed, the heat came In through all sides. It was more than the little molecular motion coolers could handle. They had been designed to work in the ship which was being heated only by the heat of the human bodies. This was too much for them, and the temperature soon rose to about a hundred and fifteen. It was not as bad as the Venerian atmosphere, for the air seemed exceedingly dry, and the men found it possible to get along without cooling suits, if they did not work. Since there was nothing they could do as yet, they had no cause to be hot.

	It was nearly dark before the men had finished their work, and the gas tanks had been recharged. All that time Arcot had spent consulting with Tonlos trying to get information about the position of the Kaxorian construction camp. Due to the long years that had passed since communications had been cut off with Kaxor, it was impossible to know much about the southern hemisphere. However, the spies that had been at work in Kaxor had gotten several maps through to the Lanorian government. The difficulty came in that Kaxor had not mapped the northern hemisphere, and therefore the two maps could not be made to align themselves very exactly. The old maps helped a great deal, but still it was impossible to do very accurate work by these means.

	It was finally determined that the Kaxorian construction camp was about 10,500 miles to the southwest. The Solarite was to start an hour after dark—they wanted to reach the camp just after nightfall, but since it was nearly four thousand miles to the west, it was necessary to wait an hour after dark in Sonor, and then make the trip, since it would be a three-hour trip, and they would in this way get there at the desired time.

	They had no fear that they would miss the camp in the dark. Such a vast landing field as would harbor those giant machines was large enough to spot at night. The lights would be visible for miles around, no doubt.

	The Solarite was moving swiftly along. The sky was slowly growing a bit lighter as they went toward the west. They were catching up on the sun. But now, as they saw the rolling ocean beneath them give way to low plains, they realized they were over Kaxorian land. The Solarite was flying very high, and as they showed no lights, and were not using the invisibility apparatus, they would be almost undetectable. Suddenly they saw the lights of a mighty city looming far off to the east.

	"Kanor, pass well to the west of it. That is their capital." Wade was at the control, Arcot was to control the projector. Now he was telling Wade the directions to follow on his course to the berth of the giant planes.

	The city had dropped far behind them now, and another, and another. They were entering a region of low hills, age-old folds in the crust of the planet, rounded off by untold ages of rains. Low they loomed against the grey horizon of the clouds.

	"Easy, Wade. We are near now." Mile after mile they shot on at about a thousand miles an hour—then suddenly they saw far off to the east a vast light that reached into the sky, and seemed to paint itself on the clouds there miles above.

	"There it is—off there—go high, and easy!"

	Swiftly the Solarite climbed into the air. They were nearly five miles above the field now. Below them they saw a field. From this height all sense of proportions seemed lost. It seemed but an ordinary field, with eighteen ordinary airplanes resting on it. One of these now was moving, and in a moment it was rising into the air! But there seemed to be no men on all the great field. They were invisibly small from this height, and as they moved about the field, overshadowed by the titanic planes, they were lost

	"They are rising—look—there are men entering those other ships! Their surprise is that they have completed the ships far ahead of the time we expected! If all that armada gets in the air, we will be helpless despite our ray—we must destroy as many as we can before they leave the ground. They are grouped and we can destroy more in less time. Quick—-drop to within a few hundred feet of the ground, and come in close to the field!"

	The Solarite sank like a stone—down they shot with a sickening lurch, as they fell the distance of five miles to the ground below. There was a sudden tremendous weight as the ship was brought to rest not more than two hundred feet from the ground. Rapidly now Wade shot it in as close to the field as he dared. The planes loomed gigantic now, their true proportions showing clearly against the brilliant light of the field. There was one mighty wave of sound coining from the loud-speaker as the planes rolled across the ground to leap gracefully into the air—half a million tons, of metal!

	From the little ship there reached out a pale beam of ghostly light, a light that was faintly grey, tinged with red and green—the ionized air as the beam. In an instant the whirr of the hundreds, thousands of giant propellers was drowned in a terrific roar of air. Great snowflakes were falling from the air before them; it was white with the solidified water vapor. Then came a titanic roar and the planet itself seemed to shake! There was a crash, a snapping and rending as a mighty fountain of dirt and rock shot high into the air, and with it, twisting, turning, hurled in a dozen directions at once, twelve titanic ships were flying high into the air! For an instant there was a silence that was oppressive, as the ray was shut off. Then again there was a roar that slowly grew to a mighty cascade of sound as the millions of tons of rock and dirt fell back. Some of it had gone miles up. Now it came down, but not with the same speed it went up. In a few moments the ground was as it had been before apparently, except that it seemed newly turned, and over it all there lay a white blanket of ice and snow. But it was quickly dissolving.

-

	HIGH above there were ten planes flying about in the air—suddenly one turned, headed for the ground far below, and was coming down at terrific speed, the wings screaming their protest as the motors pulled, ever faster, with the gravity of the planet aiding them. There was a rending, crackling crash as the wings suddenly bent back along the sides. An instant later the plane was falling freely; the wings falling, twisting, turning down. The Solarite seemed to leap as from a gun as it shot swiftly away from the spot—away and up, with a force that nailed the occupants to the floor. Then behind them was a mighty gout of light that struck to the very clouds above, and all the landscape, for miles about, was visible in the glare of the released energy.

	Back there on the plain was a great spot of loose dirt, and in the center a spot that glowed white, and seemed to bubble. It was molten.

	Nine great planes were circling in the air, then of an instant they were gone, and no man could find them, but the Solarite was darting away with a speed that defied the aim of any machine.

	High above the planes they went, for in the radio direction control Arcot could trace them. They were circling, searching for the Solarite.

	The tiny machine was invisible in the darkness, but its invisibility could not be located by the radio detectors.

	"Wade, how is it those ships can be invisible when they are driven by light, and have the light stored in them?" asked Fuller. "They are perfectly transparent. Why is it they can be made invisible without the light making them stand out?"

	"They are storing the light. It is bound—it cannot escape. You cannot see light unless it literally hits you in the eye. That cannot reach you, for it is held by its own attraction and by the special field of the big generators there."

	They seemed to be above one of the Kaxor planes now. Arcot caught the roar of the invisibility set

	"To the left, Wade—faster—hold it—left—ah!" Arcot pushed a button.

	Down from the Solarite there dropped a little canister, one of the bombs that Arcot had prepared the night before. To hit an invisible target is ordinarily difficult, but when that target is far larger than the proverbial side of a barn, it is not very difficult, at that. But now Morey was watching for the crash of the explosion, the flash of light. What sort of bomb was it that Arcot hoped would penetrate that tremendous armor?

	Suddenly there was a great spot of light—it seemed to spread with startling rapidity, a patch of light that ran, and moved. It was flying through the air at terrific speed. The light was a pale green that seemed to flow and ebb; it had a strange ghostly appearance.

	For an instant Morey and the others stared in utter surprise at it. Then suddenly Morey burst out laughing.

	"Ho—you win Arcot—that, was one they didn't think of, I'll bet! You have them on that one, and they never will put that out!"

	For an instant longer Wade looked in puzzled wonder; then he too saw the secret, and began laughing.

	"Luminous paint—and by the gallon! You had enough to paint a city with. I suppose it is radium paint, and no man has ever found how to stop radium, so they are stuck—and that plane sticks out like a sore thumb! Their invisibility may make the paint invisible, but it can't make the light it gives out invisible!"

	Indeed the luminous paint made the gigantic plane clearly visible now against the grey clouds. Visible or not, that plane was marked.

	Quickly now Arcot tried to maneuver the Solarite over another of the invisible planes, for now the danger was only from those he could not see. Suddenly he had an idea.

	"Morey—go back to the power room and change the adjustment on the meteorite avoider to half a mile!" At once Morey understood his plan, and hastened to put it into effect. The illuminated plane was diving, twisting wildly now. Suddenly Arcot focused his attention on it. The Solarite dived down toward it with sickening speed, then suddenly the gigantic bulk of the plane loomed off to the right of the tiny ship, the great metal hull, visible now, rising in austere power. They were too near, and Wade shot the machine to a greater distance—then again that ghostly beam reached out—and for just a fraction of a second it touched the giant plane.

	The titanic engine of destruction seemed suddenly to be in the grip of some Colossus so far vaster than it, that it was but a fragile toy in the terrific grip—and he closed that grip! The great plane jumped back with a terrific crash, a mighty roar of rending steel, of torn metal and snapping beams. There was a sudden crash. For an instant there came the sound as of some mighty buzz-saw as the giant propeller of one wing cut into the body of the plane as it came crushing in upon it. Then, in that instant, the great power storage tank was split open. It seemed like the bursting of a world. The Solarite was hurled back with the force of an explosion that seemed to split the very atoms of the air, and all about them was a terrific blaze of intense heat and light that seemed to sear their faces and hands with the intense rays.

	Then, in a time so short it seemed never to have happened, it was gone, and only the distant drone of the other ships' propellers came to them. There was no luminous spot. The radium paint had been destroyed in the only possible way—it was volatilized through all the atmosphere!

	The Terrestrians had known what to expect; had known what would happen; and they had not looked at the great ship in that last instant. But the Kaxorians had naturally been looking at it. The men who had never seen the sun directly, they had been looking at it, and their eyes were lidless now, for their invisibility afforded them no protection. They were temporarily blinded; they could only fly a straight course in response to the quick order of their squadron commander.

	And in that brief moment that they were unable to watch him, Arcot dropped two more bombs in quick succession. Two bright spots stuck out in the black night. No longer did these planes feel themselves invulnerable, able to meet any foe! In an instant they had put on every last trace of power, and at their top speed they were racing west, away from their tiny opponent—in the only direction that was open to them.

	But it was useless. The Solarite could pick up speed in half the time they could, and in an instant again Arcot was training the beam on the mighty splotch of light that was a fleeing plane. These planes, which had been invulnerable through sheer size, were helpless now. Through their very mass they were slow in pickup, and the lightning-fast Solarite was bearing down on them.

	Out of the dark came a ghostly beam, for an instant of time so short that before the explosive shells of the other could be trained on it, the Solarite had moved, and before it the mighty plane was crumpling, splintering under the titanic driving blow of the great wing, as it shot toward the main body of the plane at several miles a second—driving into and through it. The giant plane was twisting, turning, falling swiftly to the dark ground below—then again there came that world-rocking explosion, that mighty column of light, and there was no ship there. The companion ship had shot away from the terrific explosion with a mighty lurch, tumbling, twisting. Then there came a slow, grinding crack, and under that terrific stress the wing broke, and fell suddenly free of the plane! Turning—falling ever faster, the pilot was struggling to turn the nose of the plane up, hoping the engines might hold it from its fall. There was suddenly a mighty gout of light, a great blazing trail of light that reached out behind it—then suddenly the tail of the mighty ship was glowing white hot—flaming. Then again the plane was turning, twisting down, helpless. There was a terrific crash; the mechanical noise of its collision was followed an instant later by the greater crash, as all its energy storage was released.

	But to remind the men of the Solarite that they were not alone, there came a sudden report just behind them, and they turned to see that one of the energy bombs had just fallen short of them! In an instant the ship was shooting up at terrific speed, out of danger. It looped, turned, and was hunting, feeling with the disturbance locater for that other ship. The ships were spread out more now. In every direction they could be located—and all were leaving the scene of battle. But one by one the Solarite shot after them, and always the speed of the little ship was greater.

	Two escaped. They turned off their useless invisibility apparatus and could not be found, for, lost, in the night, they were invisible and unbeatable. Morning found the Solarite once more over Kanor, the Kaxorian capital. Arcot had learned that the language of both these peoples was almost identical. Now he was using his radio, sending his message toward the city. It was long before he got his reply. Perhaps it was that the Kaxorians were almost afraid to reply, for they had seen an awful demonstration of power!

	"I am of earth. We want only peace. We will have peace, but we prefer to have it by peaceful means, not by destroying you and your city. There is a mountain to the west of your city. In ten minutes that mountain will suffer the fate that will meet your city if you cannot agree to our terms of peace."

	Great rocky cliffs loomed before the tiny ship. They were composed of a green, heavy rock. Suddenly there reached out a thin, wan beam, a ray of light that was scarcely visible in the light of the dawn. But there was a mighty roar, a terrific tornado, and with it a fall of great snowflakes. But there was another fall. The rock suddenly moved with a terrific lunge to the right, half the mountain seemed driving against itself, moving of its own accord, and there was a vast crash of colliding rock. Then suddenly, as if by magic, great cracks appeared in the plain all about it

	The Solarite hung high above the city—and ten miles away to the west, just beyond the range of any guns that might accidentally go off. Beyond the city, off to the north, there was a vast cloud of dust settling over a mass of crushed stone. There was a low mound here, spread out wide on the flat plain. 

	We know the rest. Kaxor was but a victim of bad rulership. The ruler, lusting for greater power, seeing in the discovery of a scientist the necessary means to his ends, had made use of the discovery of the light-power condensation, and his fleet of mighty planes was the result. He had refused to yield to Arcot and the Solarite. He was found blasted by a small handlight gun. They never tried too hard to find the assassin, but many people might have been able to give information. Can we blame them? They were perhaps the most advanced people we have ever met. Their scientific discoveries are of immense value to both planets, and to those people on far out Jupiter's moons.

	But our metal supplies are no longer a source of worry. Perhaps in a million years—but who knows what man will do in a million years?

The End