Part 3

"The ships were first sighted in the big telescope when they turned it toward Mars last night. You remember that Mars is at its closest now, and they are taking a good many pictures of it. When they saw these spots of light on the disc of Mars they were at once excited and started immediate spectroscopic and radiometric observations. The fact that they showed against the disc of Mars meant that they were nearer than the planet, and by measuring the amount of energy coming from them they tried to calculate their size. The results at once proved that they could not be light because of reflection, for the energy that they emitted would require a surface of visible dimensions, and these were points. Their temperature was too low to be incandescent, so they were violating all the laws of astro-physics. By this time they had shifted sufficiently to make some estimate of their distance, shifted because of the movement of the Earth in its orbit, Dave, and so they were covering a different spot on the disc of Mars. Allowing that they were going in a straight line, they were some ten and a half million miles away. The spectroscope showed by displacement of one of the spectral lines that they were coming toward us at about 100 miles a second. The line of their flight was such that they would intercept the Earth in its orbit in about thirty hours. That means that we have about twenty to work in.

"It doesn't take any alarmist to guess that this means trouble. They would not be coming in twenty ships if they were coming on a peaceful mission. Also considering that they come in only twenty ships it shows that they have considerable confidence in those twenty. Since they are coming here without first sending a scouting party of one or two ships, I suspect that they already know that the conditions of Earth are suitable to them. To determine our conditions would require exceedingly powerful telescopes, but they are helped by the thin air of their planet. I believe that they can actually see our machines and weapons, and that they know just about what we have. I think that they are counting on cleaning up the world very easily--as indeed they would but for one factor, for they have atomic energy. Wright, do you remember that we decided to use electronic rockets to drive the car, once we discovered atomic energy? And that having discovered material energy, we naturally decided not to? Well, they have electronic rockets. This makes me feel sure that that means that they have atomic energy, but have no material energy."

"Fine Steve. Your reasoning is most admirable--but will you please translate 'electronic rocket' and a few of those other terms into English? And otherwise make yourself clear to the layman?"

"Well, I suppose I have no right to call a cathode ray tube an electronic rocket, but when a cathode ray tube gets that big it really needs a new name. The idea is the same as that of a rocket. You know the experiments the Germans, the millionaire Opel, and others carried out in 1927 with rocket automobiles? They had a terrible time with their rockets because the heat of one set off the next. The result was a disastrous explosion--and they had a whole ocean of air to cool them! What would a rocket do in free space? Also remember the principle of a rocket is that you shoot particles out of the rear at a very high speed and thus impart the kick to the ship. The electronic rocket does the same thing--but instead of shooting molecules of hot gas, it shoots electrons, a giant cathode ray tube such as Coolidge had in 1927, but his was so small that the kick was immeasurable. Remember that as the velocity of the electrons approaches that of light, the mass increases and so the electrons as shot from a cathode ray rocket may weigh as much as a milligram. The problem of propulsion then is not hard with atomic energy to supply the terrific voltages needed to run the tube. But the cathode rays are going to be their first weapon. Cathode rays are absorbed by any object they hit, and their terrific energy is converted to heat. They are deadly in themselves, and the heat is of course deadly. They will also have heat rays. I can make a heat ray with atomic energy, though mine is derived from material. The only way we can fight them is to know beforehand what we are to meet. This is to be a war for a world, and the war will be a battle of titanic forces. The weaker of the forces will be a million times greater than anything man has ever known before, and either of these two forces would, if fully applied, blast our planet from its place around the sun! Such forces can not be withstood. They must be annulled, deflected, or annihilated by some greater force. Only when we know what to expect can we fight them, and live. Remember, if they once succeeded in getting one weak spot in our armor, we can never have another chance, and the world can never hope to fight them--mere armies and a navy or two, with a couple of air forces thrown in--what would they amount to? The energy of atoms could destroy them like paper in a blow-torch--think what would happen to one of those beautifully absorbing grey battleships if a heat ray touched it! Their eighteen-inch steel armor would not melt--it would boil away! A submarine would be no safer--they could explode the water about it into steam and crush it. The effect of a heat ray in water is just that--the water is converted to steam so suddenly that there is a terrific explosion. The cathode rays could sweep an army out of existence as hose might wash away an army of mud soldiers. They won't have gases. They will have no use for them. They could wipe a city off the map, leave only a great crater in the scarred Earth, while men were getting ready to lay a gas barrage. A shell would certainly just bounce off of the armor of my ship and I suspect that it would do the same with the Martian ships. Earth has only one weapon that can even bother them! And that one weapon is the one factor they did not figure on! It is the 'Terrestrian.' But now, if we want to make that one factor upset the whole equation, we have to calculate how to make its value a maximum, and to do that we have to know every other factor in the equation. I have suggested two weapons they will have, the cathode rays and the heat ray. They will, of course, have others; they will have atomic bombs, and I am sure that they will find us so dangerous that they will be willing to lose a ship and crash us. This gives us something else to avoid. Can any of you think of something else?"

"Good Lord Steve, haven't you thought of enough?"

"Plenty, Dave, but it isn't considered good form in military proceedings to permit the enemy to surprise you. In fact, it is highly probable that if he does, you will get a new form, one more adapted to aerial transit."

"Yes, that's true, too. But I remember reading once that ultra-violet light was invisible, and very dangerous to the body. I wonder if they will use that?"

"They may, but I greatly doubt it. Air is very nearly opaque to ultra-violet light, above a certain limit, and below that limit it is not very harmful. The infra-red heat rays, though, are going to be a very great menace. I can't think of any way to make them harmless. Of course, the polished iridium shell of the ship will protect us from the sides, as the heat will all be reflected. The difficulty will be that the heat will fuse the window, and thus attack us. The quartz glass is nearly opaque to heat rays, as is all glass. Being opaque, it absorbs it, 'cuts it out' as we say. The result will be that the glass will melt instantly, whereupon we will go very quickly. The idea of putting a polished metal shutter before the window is the one we will have to adopt, but we must modify it somehow. The heat rays will be turned back all right--and so will the light rays. The question is to shut out heat and let in light. Any suggestions?"

"I wonder if there isn't some selective reflector that we could use, Dr. Waterson?"

"That is a good idea, Wright--but I don't know of any that will pass all the light and reflect all the heat!"

"What is a selective reflector, Steve?"

"There are lots of things that have that property Dave, gold leaf is one, it can transmit green light--that is you can see green light through it, but it reflects yellow light--the complement of the green it transmits. There are a great many organic dyes that are one color when you look at them and the complement of that color when you look through them. The trouble is we need one that transmits the visible portion of the spectrum and--boy--that's it, Wright, that's it--spectrum--take a totally reflecting diffraction grating, reflect out all that part of the spectrum that we don't want, take what we do, pass it through a prism to recombine it to white light, then through lenses so we can see as if through a telescope! We will have absolutely cold light!"

"Again it sounds good, but I'd like to hear it in English, Steve."

"The idea is to take a diffraction grating, a piece of metal with, usually, 14,438 lines to the inch ruled on it, and previously highly polished, so that it reflects most of the light that hits it. Now it is reflected at different angles, so that we have a spectrum. The spectrum spreads out light and heat waves as well--I use the reflection grating as no material will pass the heat rays, and it then is possible to reflect out of the car again those rays we do not want. The light, which we do want, we will pass through a prism which will recombine it to white light. A prism can either split up light into different colors, or recombine them to white. Lenses then will be needed to make the images clear. The effect will be much the same as a telescope. And that takes care of the heat waves. The cathode rays, luckily won't bother us for the car is already charged strongly negative, and negatively charged electrons will be strongly repelled, as they are in the grid of a vacuum tube, so will never hit us. The bombs constitute the worst menace. The only defense we have against them is the very doubtful one of not being there when they are. That is a good policy in any case.

"As a last precaution--a bit grim--I will arrange it so that if the 'Terrestrian' is damaged to the point of utter helplessness we can, by pushing a single button, explode the entire car--as material energy. It will utterly destroy everything within a radius of a hundred miles, and damage everything within a much greater radius. I believe it will not be serious enough to change the Earth's orbit, though."

"Good--cheerful man, aren't you, Steve! Now what have we to meet that delightful array?"

"We have things even more delightful. Our heat ray is considerably more powerful, I imagine. It is generated by a force ten thousand times as great. Our bombs will be worse. Wright, I wish you would make about a hundred shells that will explode with the full thirty-five thousand ton equivalent of dynamite. And then we will have everything they have that is going to be effective, and have it in a more concentrated form. Can any of you suggest anything else?"

"Steve, you said that your car was nearly pure iridium on the outside, and that is very inert. The outside of their ship will be polished too, won't it?"

"Probably--though I don't believe they were expecting to meet a heat ray."

"Well, I wonder if there isn't some chemical you could spray out that would tarnish their ship, without hurting your iridium ship? Then it wouldn't be polished and would absorb your heat rays."

"That's a good idea, Dave. I might use a sulphide--nearly all sulphides are colored, and form very easily and rapidly. Or I might use liquid ozone. That will tarnish almost anything to an oxide, which is also apt to be colored. I could certainly heat the ship that way, but I wonder--I'm afraid that the oxide or sulphide would break down too easily. There is only one metal that they might use on which that would work, namely steel. Iron sulphide is black, stable, and will not decompose readily. The oxide forms readily, is highly colored, and will not decompose before the metal is incandescent, or even melted. The only difficulty is that steel is so readily attacked, that they wouldn't use it. They would probably coat it with an inert metal, silver for instance. That forms a black sulphide very readily. I'm afraid that won't work Dave. But Wright, I think that it would be a good idea to develop a few of those field theory equations in a different way. Try integrating number two-six-thirty-nine--I think that's it--and between the limits of equation one-four-twenty-three and zero. I have an idea that a little development of that idea will give us a beam that will be very useful. We haven't time to make much apparatus, but I think the result will be near enough to the space curving projector to allow us to change the extra projectors we have in the laboratory to fit. Also, try calculating the arrangement we will need for the heat eliminator, please. I'm going to give Dave his first lesson in space navigation. We'll be back about noon--if at all!" But Gale caught the wink, so the effect was lost.

* * * * *

Ten thousand miles out in free space the practice began. As Waterson pointed out, it would require some mighty poor handling to hit the Earth now. For the first time in Gale's life he could practice with a machine with no fear of hitting anything.

When the ship slanted down in a long graceful glide, to enter the hangar doors that noon, Gale was in control. The controls of the ship were remarkably easy to master and extremely simple. The one thing that was hard to master was the tremendous range of power. It could be changed in a smooth climb from a fraction of a horsepower to billions! The first attempts had been a bit hard on the passengers, the seat straps coming in for their share of use.

When they returned to the laboratory, they found Wright had just prepared a light lunch, and at once began to demolish it. Six hours between breakfast and lunch is conducive to a husky appetite.

Wright had finished the integration on the machine, and had calculated the mathematics of the heat eliminator in a little less than four hours. The results were very satisfactory, and in the remaining time he had converted six of the extra projectors to their new use, and had them ready for installation. After lunch the men began on the construction of the heat eliminators. Two were to be installed, one for the observer as well as one for the pilot. The heavier work of installing the projectors and the iridium shield was reserved for later in the afternoon.

By six that evening, the new projectors were completely installed and the connections made, and the great iridium shield was cooling from blinding incandescence in its mold. It would be installed that night, but now they felt that a rest and a meal were due them. They had been working under a great strain that afternoon, for they knew that they must get that machine ready before the Martians reached Earth, and there was a great deal to do. After the brief dinner they went out to the shining "Terrestrian." As yet, the new projectors had not been tried.

Gracefully the great shining shell backed out into the ruddy glory of the sinking sun, the red light had turned the desert to a sea of rolling fire, with here and there a wave that showed dark--a mound. In the far distance the purple hills of Nevada seemed like distant islands in this burning sea, and above it rode this lone, shining ship, magnificently iridescent in the setting sun. Now it stopped, hovered, then suddenly a pile of metal ingots that lay to one side of the laboratory leaped into the air and shot toward it--then paused in mid-air, hung poised for an instant, then sank lightly to the ground. Now the sand of the desert began to roll into some strange wave that began just beneath the ship, then sped away--further--till it died in the far distance, by means of an invisible beam. A wall of sand thirty feet high had been built in an instant, and it extended as far as the eye could reach! Now the ship settled, and slowly, light as a feather for all its three thousand tons of metal, it glided into the hangar.

[Illustration: _Now the sand of the desert began to roll into some strange wave that began just beneath the ship, then sped away--further--till it died in the far distance._]

"Man Steve, that works! How long a range has it? And please tell me about it now you are sure it works!"

"I don't know just how long a range it has--it affected the sand as far as we could see, and we were using very little power. It is just a modification of the space curving apparatus. It projects a beam of gravity, and theoretically at least it has an infinite range; and it certainly has a whale of a lot of power. I can use a good deal of the power too, for the strain of the attraction is taken off the mountings and the ship, and put on space itself! The gravity projector is double and projects a beam of the gravity ray forward and an equally powerful beam of the space curve behind. The two rays are controlled by the same apparatus, and so are always equal. The result is that no matter how great a load I put on it, the entire load is expended in trying to bend space!"

That night work was carried on under the floodlighting from the ship's great light projectors. The entire region was illuminated, and work was easy. Waterson had been instructed to take a rest when he seemed bent on continuing his work. Even his great body could not keep up that hard labor forever, and forty-eight hours of work will make any man nervous. With a crisis such as this facing him, he certainly needed rest. He agreed, provided they would call him in two hours. Two hours later Gale walked about a mile from the laboratory, and called. He then returned and continued his work on the placement of the shield. It had been placed, polished, and tiny holes bored in it for the heat eliminator inside of four hours. It was operated by an electric motor, controlled from within. It could be lowered and leave the window clear, but when in position its polished surface made it perfectly safe against heat rays. The work had just been completed, when Waterson reappeared looking decidedly ruffled.

"Say, I thought you two promised to call me in two hours! It's been just four, and I woke up myself!"

"But Steve, I did call you and you didn't hear me. I didn't say I'd wake you in two hours."

* * * * *

It was shortly afterwards that news of the coming invasion was made public. And with the news came the wild panics, even mad, licentious outbreaks all over the world. Man saw himself helpless before mighty enemies whom he could not resist. Never had such a complete disruption of business taken place in so short a time. Things were done that night in a terrible spirit of "we die tomorrow, we play today." The terrible jams in the cities caused the deaths of hundreds of thousands. They wanted to flee the cities, get into the woods and hide like some animal. Within an hour no news could reach most of them, and though Waterson had told of his ship, told immediately, given every government official announcements concerning it, still the mad dance went on. But to those that had stayed near the radio sets, this news brought relief. No television pictures of it could be broadcast for many hours, as there was no portable equipment within several hundreds of miles, and the men were working on the ship.

That night the three men took turns watching by the radio set for news. The Martians were due to land somewhere on Earth that morning. It would probably be a temporary landing in some land that was just at dawn. And it was so. But the "Terrestrian" must not be taken by surprise.

Waterson was to have the morning watch. Unlike the others, he did not sit by the radio set. He answered the few messages he received, but the entire four hours of his watch he spent working with Bartholemew. The equations he was working with seemed new, strange, and they had terrific import to the understanding. It was but a few minutes before the Martians landed when he had gotten the final result. At once he called the two others.

"Wright, if that equation means what I think it does, we have something that will give us a tremendous advantage! I feel sure that the Martians have actually worked out the problem of the atom by pure brain power--no machines aided them, else they too would have discovered the secret of matter. That machine has made it possible for us to work out problems to meet them. But as they may land any minute now, let's begin on this. We need two of these projectors in front, and two at the stern. If you will start on the actual projectors, I'll start the instrument end. Come on Dave."