III

Swiftly Arcot's sleek cruiser sped toward New York and the Arcot

Laboratories. They had halted briefly at the headquarters ship of the

Earth-Venus forces to report on their experience; and alone again, the

three scientists were on their way home.

With their course set, Arcot spoke to the others. "Well, fellows, what

are your opinions on--what we've seen? Wade, you're a chemist--tell us

what you think of the explosion of the ship, and of the strange color of

our molecular ray in their air."

Wade shook his head doubtfully. "I've been trying to figure it out, and

I can't quite believe my results. Still, I can't see any other

explanation. That reddish glow looked like hydrogen ions in the air. The

atmosphere was certainly combustible when it met ours, which makes it

impossible for me to believe that their air contained any noticeable

amount of oxygen, for anything above twenty per cent oxygen and the rest

hydrogen would be violently explosive. Apparently the gas had to mix

liberally with our air to reach that proportion. That it didn't explode

when ionized, showed the absence of hydro-oxygen mixture.

"All the observed facts except one seem to point to an atmosphere

composed largely of hydrogen. That one--there are beings living in it! I

can understand how the Venerians might adapt to a different climate, but

I can't see how anything approaching human life can live in an

atmosphere like that."

Arcot nodded. "I have come to similar conclusions. But I don't see too

much objection to the thought of beings living in an atmosphere of

hydrogen. It's all a question of organic chemistry. Remember that our

bodies are just chemical furnaces. We take in fuel and oxidize it, using

the heat as our source of power. The invaders live in an atmosphere of

hydrogen. They eat oxidizing fuels, and breathe a reducing atmosphere;

they have the two fuel components together again, but in a way different

from our method. Evidently, it's just as effective. I'm sure that's the

secret of the whole thing."

"Sounds fairly logical." Wade agreed. "But now I have a question for

you. Where under the sun did these beings come from?"

Arcot's reply came slowly. "I've been wondering the same thing. And the

more I wonder, the less I believe they did come from--under our sun.

Let's eliminate all the solar planets--we can do that at one fell swoop.

It's perfectly obvious that those ships are by no means the first crude

attempts of this race to fly through space. We're dealing with an

advanced technology. If they have had those ships even as far away as

Pluto, we should certainly have heard from them by now.

"Hence, we've got to go out into interstellar space. You'll probably

want to ram some of my arguments down my throat--I know there is no star

near enough for the journey to be made in anything less than a couple of

generations by all that's logical; and they'd freeze in the interstellar

cold doing it. There is no _known_ star close enough--but how about

unknowns?"

"What have they been doing with the star?" Morey snorted. "Hiding it

behind a sun-shade?"

Arcot grinned. "Yes. A shade of old age. You know a sun can't radiate

forever; eventually they die. And a dead sun would be quite black, I'm

sure."

"And the planets that circle about them are apt to become a wee bit cool

too, you know."

"Agreed," said Arcot, "and we wouldn't be able to do much about it. But

give these beings credit for a little higher order of intelligence. We

saw machines in that space ship that certainly are beyond us! They are

undoubtedly heating their planets with the same source of energy with

which they are running their ships.

"I believe I have confirmation of that statement in two things. They are

absolutely colorless; they don't even have an opaque white skin. Any

living creature exposed to the rays of a sun, which is certain to emit

some chemical rays, is subject to coloration as a protection against

those rays. The whites, who have always lived where sunlight is weakest,

have developed a skin only slightly opaque. The Orientals, who live in

more tropical countries, where less clothes and more sun is the motto,

have slightly darker skins. In the extreme tropics Nature has found it

necessary to use a regular blanket of color to stop the rays. Now

extrapolating the other way, were there no such rays, the people would

become a pigmentless race. Since most proteins are rather translucent,

at least when wet, they would appear much as these beings do. Remember,

there are very few colored proteins. Hemoglobin, such as in our blood,

and hemocyanin, like that in the blue blood of the Venerians, are

practically unique in that respect. For hydrogen absorption, I imagine

the blood of these creatures contains a fair proportion of some highly

saturated compound, which readily takes on the element, and gives it up

later.

"But we can kick this around some more in the lab."

Before starting for New York, Arcot had convinced the officer in charge

that it would be wise to destroy the more complete of the invaders'

ships at once, lest one of them manage to escape. The fact that none of

them had any rays in operation was easily explained; they would have

been destroyed by the Patrol if they had made any show of weapons. But

they might be getting some ready, to be used in possible escape

attempts. The scientists were through with their preliminary

investigations. And the dismembered sections would remain for study,

anyway.

The ships had finally been rayed apart, and when the three had left,

their burning atmosphere had been sending mighty tongues of flame a mile

or more into the air. The light gas of the alien atmosphere tended to

rise in a great globular cloud, a ball that quickly burned itself out.

It had not taken long for the last of the machines to disintegrate under

the rays. There would be no more trouble from them, at any rate!

Now Morey asked Arcot if he thought that they had learned all they could

from the ships; would it not have been wiser to save them, and

investigate more fully later, taking a chance on stopping any sudden

attack by surviving marauders by keeping a patrol of Air Guards there.

To which Arcot replied, "I thought quite a bit before I suggested their

destruction, and I conferred for a few moments with Forsyth, who's just

about tops in biology and bacteriology. He said that they had by no

means learned as much as they wished to, but they'd been forced to leave

in any event. Remember that pure hydrogen, the atmosphere we were

actually living in while on the ship, is quite as inert as pure

oxygen--when alone. But the two get very rough when mixed together. The

longer those ships lay there the more dangerously explosive they became.

If we hadn't destroyed them, they would have wrecked themselves. I still

think we followed the only logical course.

"Dr. Forsyth mentioned the danger of disease. There's a remote

possibility that we might be susceptible to their germs. I don't believe

we would be, for our chemical constitution is so vastly different. For

instance, the Venerians and Terrestrians can visit each other with

perfect freedom. The Venerians have diseases, and so do we, of course;

but there are things in the blood of Venerians that are absolutely

deadly to any Terrestrian organism. We have a similar deadly effect on

Venerian germs. It isn't immunity--it's simply that our respective

constitutions are so different that we don't need immunity. Similarly,

Forsyth thinks we would be completely resistant to all diseases brought

by the invaders. However, it's safer to remove the danger, if any,

first, and check afterward."

The three men sped rapidly back to New York, flying nearly sixty miles

above the surface of the Earth, where there would be no interfering

traffic, till at length they were above the big city, and dropping

swiftly in a vertical traffic lane.

Shortly thereafter they settled lightly in the landing cradle at the

Arcot Laboratories. Arcot's father, and Morey's, were there, anxiously

awaiting their return. The elder Arcot had for many years held the

reputation of being the nation's greatest physicist, but recently he had

lost it--to his son. Morey Senior was the president and chief

stockholder in the Transcontinental Air Lines. The Arcots, father and

son, had turned all their inventions over to their close friends, the

Moreys. For many years the success of the great air lines had been

dependent in large part on the inventions of the Arcots; these new

discoveries enabled them to keep one step ahead of competition, and as

they also made the huge transport machines for other companies, they

drew tremendous profits from these mechanisms. The mutual interest,

which had begun as a purely financial relationship, had long since

become a close personal friendship.

As Arcot stepped from his speedster, he called immediately to his

father, telling of their find, the light-matter plate.

"I'll need a handling machine to move it. I'll be right back." He ran to

the elevator and dropped quickly to the heavy machinery lab on the lower

floor. In a short time he returned with a tractor-like machine equipped

with a small derrick, designed to get its power from the electric mains.

He ran the machine over to the ship. The others looked up as they heard

the rumble and hum of its powerful motor. From the crane dangled a

strong electro-magnet.

"What's that for?" asked Wade, pointing to the magnet. "You don't expect

this to be magnetic, do you?"

"Wait and see!" laughed Arcot, maneuvering the handling machine into

position. One of the others made contact with the power line, and the

crane reached into the ship, lowering the magnet to the plate of

crystal. Then Arcot turned the power into the lifting motor. The hum

rose swiftly in volume and pitch till the full load began to strain the

cables. The motor whined with full power, the cables vibrating under the

tension. The machine pulled steadily, until, to Arcot's surprise, the

rear end of the machine rose abruptly from the floor, tipping forward.

"Well--it _was_ magnetic, but how did you know?" asked the surprised

Wade. Since the ship was made of the Venerian metal, coronium, which was

only slightly magnetic, the plate was obviously the magnet's only load.

"Never mind. I'll tell you later. Get an I-beam, say about twenty feet

long, and see if you can't help lift that crazy mass. I think we ought

to manage it that way."

And so it proved. With two of them straddling the I-beam, the leverage

was great enough to pull the plate out. Running it over to the elevator,

they lowered the heavy mass, disconnected the cable, and rode down to

Arcot's laboratory. Again the I-beam and handling machine were brought

into play, and the plate was unloaded from the car. The five men

gathered around the amazing souvenir from another world.

"I'm with Wade in wondering how you knew the plate was magnetic, son,"

commented the elder Arcot. "I can accept your explanation that the stuff

is a kind of matter made of light, but I know you too well to think it

was just a lucky guess. How did you know?"

"It really was pretty much of a guess, Dad, though there was some logic

behind the thought. You ought to be able to trace down the idea! How

about you, Morey?" Arcot smiled at his friend.

"I've kept discreetly quiet," replied Morey, "feeling that in silence I

could not betray my ignorance, but since you ask me, I can guess too. I

seem to recall that light is affected by a powerful magnet, and I can

imagine that that was the basis for your guess. It has been known for

many years, as far back as Clerk Maxwell, that polarized light can be

rotated by a powerful magnet."

"That's it! And now we may as well go over the whole story, and tell Dad

and your father all that happened. Perhaps in the telling, we can

straighten out our own ideas a bit."

For the next hour the three men talked, each telling his story, and

trying to explain the whys and wherefores of what he had seen. In the

end all agreed on one point: if they were to fight this enemy, they

_must_ have ships that could travel though space with speed to match

that of the invaders, ships with a self-contained source of power.

During a brief lull in the conversation, Morey commented rather

sarcastically: "I wonder if Arcot will now kindly explain his famous

invisible light, or the lost star?" He was a bit nettled by his own

failure to remember that a star could go black. "I can't see what

connection this has with their sudden attack. If they were there, they

must have developed when the star was bright, and as a star requires

millions of years to cool down, I can't see how they could suddenly

appear in space."

Before answering, Arcot reached into a drawer of his desk and pulled out

an old blackened briar pipe. Methodically he filled it, a thoughtful

frown on his face; then carefully lighting it, he leaned back, puffing

out a thin column of gray smoke.

"Those creatures must have developed on their planets before the sun

cooled." He puffed slowly. "They are, then, a race millions of years

old--or so I believe. I can't give any scientific reason for this

feeling; it's merely a hunch. I just have a feeling that the invaders

are old, older than our very planet! This little globe is just about two

billion years old. I feel that that race is so very ancient they may

well have counted the revolutions of our galaxy as, once every twenty or

thirty million years, it swung about its center.

"When I looked at those great machines, and those comparatively little

beings as they handled their projectors, they seemed out of place. Why?"

He shrugged. "Again, just a hunch, an impression." He paused again, and

the slow smoke drifted upward.

"If I'm granted the premise that a black, dead star is approaching the

Solar System, then my theorizing may seem more logical. You agree?" The

listeners nodded and Arcot continued. "Well--I had an idea--and when I

went downstairs for the handling machine, I called the Lunar

Observatory." He couldn't quite keep a note of triumph out of his voice.

"Gentlemen--some of the planets have been misbehaving! The outermost

planets, and even some of those closer to the sun have not been moving

as they should. A celestial body of appreciable mass _is_ approaching

the System; though thus far nothing has been seen of the visitor!"

A hubbub of excited comment followed this startling revelation. Arcot

quieted them with an upraised hand. "The only reason you and the world

at large haven't heard about this as yet is the fact that the

perturbation of the planets is so very slight that the astronomers

figured they might have made an error in calculation. They're

rechecking now for mistakes.

"To get back to my visualization--It must have been many millions of

years ago that life developed on the planets of the black star, a warm

sun then, for it was much younger. It was probably rather dim as suns go

even its younger days. Remember, our own sun is well above average in

brilliance and heat radiation.

"In those long-gone ages I can imagine a race much like ours developing,

differing chemically, in their atmosphere of hydrogen; but the chemical

body is not what makes the race, it's the thought process. They must

have developed, and then as their science grew, their sun waned. Dimmer

and dimmer it became, until their planets could not maintain life

naturally. Then they had to heat them artificially. There is no question

as to their source of power; they had to use the energy of matter--so

called atomic energy--for no other source would be great enough to do

what had to be done. It is probable that their science had developed

this long before their great need arose.

"With this must also have come the process of transmutation, and the

process they use in driving their interstellar cruisers. I am sure those

machines are driven by material energy.

"But at last their star was black, a closed star, and their cold, black

planets must circle a hot, black sun forever! They were trapped for

eternity unless they found a way to escape to some other stellar system.

They could not travel as fast as light, and they could escape only if

they found some near-by solar system. Their star was dead--black. Let's

call it Nigra--the Black One--since like every other star it should have

a name. Any objection?"

There was none, so Arcot continued:

"Now we come to an impossibly rare coincidence. That two suns in their

motion should approach each other is beyond the point of logic. That

both suns have a retinue of planets approaches the height of the

ridiculous. Yet that is what is happening right now. And the Nigrans--if

that's the correct term--have every intention of taking advantage of

the coincidence. Since our sun has been visible to them for a long, long

time, and the approaching proximity of the suns evident, they had lots

of time to prepare.

"I believe this expedition was just an exploratory one; and if they can

send such huge machines and so many of them, for mere exploration, I'm

sure they must have quite a fleet to fight with.

"We know little about their weapons. They have that death ray, but it's

not quite as deadly as we might have feared, solely because our ships

could outmaneuver them. Next time, logically, they'll bring with them a

fleet of little ships, carried in the bellies of those giants, and

they'll be a real enemy. We'll have to anticipate their moves and build

to circumvent them.

"As for their ray, I believe I have an idea how it works. You're all

familiar with the catalytic effects of light. Hydrogen and chlorine will

stand very peacefully in the same jar for a long time, but let a strong

light fall on them, and they combine with terrific violence. This is the

catalytic effect of a vibration, a wave motion. Then there is such a

thing as negative catalysis. In a certain reaction, if a third element

or compound is introduced, all reaction is stopped. I believe that's the

principle of the Nigran death ray; it's a catalyst that simply stops the

chemical reactions of a living body, and these are so delicately

balanced that the least resistance will upset them."

Arcot halted, and sat puffing furiously for a moment. During his

discourse the pipe had died to an ember; with vigorous puffing he tried

to restore it. At last he had it going and continued.

"What other weapons they have we cannot say. The secret of invisibility

must be very old to them. But we'll guard against the possibility by

equipping our ships against it. The only reason the patrol ships aren't

equipped already is that invisibility is useless with modern criminals;

they all know the secret and how to fight it."

Morey interrupted with a question.

"Arcot, it's obvious that we have to get out into space to meet the

enemy--and we'll have to have freedom of movement there. How are we

going to do it? I was wondering if we could use Wade's system of storing

the atomic hydrogen in solution. That yields about 100,000 calories for

every two grams, and since this is a method of storing heat energy, and

your molecular motion director is a method of converting heat into

mechanical work with 100 per cent efficiency, why not use that? All we

need, really, is a method of storing heat energy for use while we're in

space."

Arcot exhaled slowly before answering, watching the column of smoke

vanish into the air.

"I thought of that, and I've been trying to think of other, and if

possible, better, cheaper, and quicker ways of getting the necessary

power.

"Let's eliminate the known sources one by one. The usual ones, the ones

men have been using for centuries, go out at once. The atomic hydrogen

reaction stores more energy per gram than any other chemical reaction

known. Such things as the storage battery, the electro-static condenser,

the induction coil, or plain heat storage, are worthless to us. The only

other method of storing energy we know of is the method used by the

Kaxorians in driving their huge planes.

"They use condensed light-energy. This is efficient to the ultimate

maximum, something no other method can hope to attain. Yet they need

huge reservoirs to store it. The result is still ineffective for our

purpose; we want something we can put in a small space; we want to

condense the light still further. That will be the ideal form of energy

storage, for then we will be able to release it directly as a heat ray,

and so use it with utmost efficiency. I think we can absorb the released

energy in the usual cavity radiator."

A queer little smile appeared on Arcot's face. "Remember--what we want

is light in a more condensed form, a form that is naturally stable, and

that does not need to be held in a bound state, but actually requires

urging to bring about the release of energy. For example--"

A shout from Wade interrupted him. "That's really rare! _Whoo_--I have

to hand it to you! That takes all the prizes!" He laughed delightedly.

In puzzled wonder Morey and the two older men looked at him, and at

Arcot who was grinning broadly now.

"Well, I suppose it must be funny," Morey began, then hesitated. "Oh--I

see--say, that _is_ good!" He turned to his father. "I see now what he's

been driving at. It's been right here under our noses all the time.

"The light-matter windows we found in the wrecked enemy ships contain

enough bound light-energy to run all the planes we could make in the

next ten years! We're going to have the enemy supply us with power we

can't get in any other way. I can't decide, Arcot, whether you deserve a

prize for ingenuity, or whether we should receive booby-prizes for our

stupidity."

Arcot Senior smiled at first, then looked dubiously at his son.

"There's definitely plenty of the right kind of energy stored there--but

as you suggested, the energy will need encouragement to break free. Any

ideas?"

"A couple. I don't know how they'll work, of course; but we can try."

Arcot puffed at his pipe, serious now as he thought of the problems

ahead.

Wade interposed a question. "How do you suppose they condense that light

energy in the first place, and, their sun being dead, whence all the

light? Back to the atom, I suppose."

"You know as much as I do, of course, but I'm sure they must break up

matter for its energy. As for the condensation problem, I think I have a

possible solution of that too--it's the key to the problem of release.

There's a lot we don't know now--but we'll have a bigger store of

knowledge before this war is over--if we have anything at all!" he added

grimly. "It's possible that man may lose knowledge, life, his planets

and sun--but there's still plenty of hope. We're not finished yet."

"How do you think they got their energy loose?" asked

Wade. "Do you think those big blocks of what appeared to be silver were

involved in the energy release?"

"Yes, I do. Those blocks were probably designed to carry away the power

once it was released. How the release was accomplished, though, I don't

know. They couldn't use material apparatus to start their release of

material energy; the material of the apparatus might 'catch fire' too.

They had to have the disintegrating matter held apart from all other

matter. This was quite impossible, if you are going to get the energy

away by any method other than by the use of fields of force. I don't

think that is the method. My guess is that a terrific current of

electricity would accomplish it if anything would.

"How then are we going to get the current to it? The wires will be

subject to the same currents. Whatever they do to the matter involved,

the currents will do to the apparatus--except in one case. If that

apparatus is made of _some other kind of matter_, then it wouldn't be

affected. The solution is obvious. Use some of the light-matter. What

will destroy light-matter, won't destroy electricity-matter, and what

will destroy electricity-matter, won't disturb light-matter.

"Do you remember the platform of light-metal, clear as crystal? It must

have been an insulating platform. What we started as our assumptions in

the case of the light-metal, we can now carry further. We said that

electricity-metals carried electricity, so light-metals would carry or

conduct light. Now we know that there is no substance which is

transparent to light, that will carry electricity by metallic

conduction. I mean, of course, that there is no substance transparent to

light, and at the same time capable of carrying electricity by

electronic transmission. True, we have things like NaCl solutions in

ordinary H_{2}O which will carry electricity, but here it's ionic

conduction. Even glass will carry electricity very well when hot; when

red hot, glass will carry enough electricity to melt it very quickly.

But again, glass is not a solid, but a viscous liquid, and it is again

carried by ionic conduction. Iron, copper, sodium, silver, lead--all

metals carry the current by means of electron drift through the solid

material. In such cases we can see that no transparent substance

conducts electricity.

"Similarly, the reverse is true. No substance capable of carrying

electricity by metallic conduction is transparent. All are opaque, if in

any thickness. Of course, gold is transparent when in leaf form--but

when it's that thin it won't conduct very much! The peculiar condition

we reach in the case of the invisible ship is different. There the

effects are brought about by the high frequency impressed. But you get

my point.

"Do you remember those wires that we saw leading to that little box of

the reflecting material? So perfectly reflecting it was that we didn't

see it. We only saw where it must be; we saw the light it reflected.

That was no doubt light-matter, a non-metal, and as such, non-conductive

to light. Like sulphur, an electric non-metal, it reflected the base of

which it was formed. Sulphur reflects the base of which it was formed.

Sulphur reflects electricity and--in the crystalline form--passes light.

This light-non-metal did the same sort of thing; it reflected light and

passed electricity. It was a conductor.

"Now we have the things we need, the matter to disintegrate, and the

matter to hold the disintegrating material in. We have two different

types of matter. The rest is obvious--but decidedly not easy. They have

done it, though; and after the war is over, there should be many of

their machines drifting about in space waiting to give up their

secrets."

Arcot Senior clapped his son on the back. "A fair foundation on which to

start, anyway. But I think it's time now that you got working on your

problem; and since I'm officially retired, I'm going downstairs. You

know I'm working in my lab on a method to increase the range and power

of your projector for the molecular motion field. Young Norris is

helping me, and he really has ideas. I'll show you our math later."

The party broke up, the three younger men staying in their own labs, the

older men leaving.