The Collected Stories of Arthur C. Clarke (16 page)

It was much clearer now. The bright nucleus
was
pulsating, and faint knots of light were moving slowly outward along the radiating filaments. As he stared, fascinated, Lindsey suddenly remembered a glimpse he had once of an amoeba under the microscope. Apparently the same thought had occurred to the Sub-Lieutenant.

‘It—it looks alive!’ he whispered incredulously.

‘I know,’ said Lindsey. ‘What do you think it is?’

The other hesitated for a while. ‘I remember reading once that Appleton or someone had detected patches of ionisation low down in the atmosphere. That’s the only thing it can be.’

‘But its structure! How do you explain that?’

The other shrugged his shoulders. ‘I can’t,’ he said bluntly.

It was vertically beneath them now, disappearing into the blind area at the centre of the screen. While they were waiting for it to emerge again they had another look at the ocean below. It was uncanny; there was still absolutely nothing to be seen. But the radar could not lie. Something
must
be there—

It was fading fast when it reappeared a minute later, fading as if the full power of the radar transmitter had destroyed its cohesion. For the filaments were breaking up, and even as they watched the ten-mile-long oval began to disintegrate. There was something awe-inspiring about the sight, and for some unfathomable reason Lindsey felt a surge of pity, as though he were witnessing the death of some gigantic beast. He shook his head angrily, but he could not get the thought out of his mind.

Twenty miles away, the last traces of ionisation were dispersing to the winds. Soon eye and radar screen alike saw only the unbroken waters of the Atlantic rolling endlessly eastwards as if no power could ever disturb them.

And across the screen of the great indicator, two men stared speechlessly at one another, each afraid to guess what lay in the other’s mind.

The Fires Within

First published in
Fantasy
, August 1947, as by ‘E. G. O’Brien’

Collected in
Reach for Tomorrow

‘This,’ said Karn smugly, ‘will interest you. Just take a look at it!’

He pushed across the file he had been reading, and for the
nth
time I decided to ask for his transfer or, failing that, my own.

‘What’s it about?’ I said wearily.

‘It’s a long report from a Dr Matthews to the Minister of Science.’ He waved it in front of me. ‘Just read it!’

Without much enthusiasm, I began to go through the file. A few minutes later I looked up and admitted grudgingly: ‘Maybe you’re right—this time.’ I didn’t speak again until I’d finished….

My dear Minister (the letter began). As you requested, here is my special report on Professor Hancock’s experiments, which have had such unexpected and extraordinary results. I have not had time to cast it into a more orthodox form, but am sending you the dictation just as it stands.

Since you have many matters engaging your attention, perhaps I should briefly summarise our dealings with Professor Hancock. Until 1955, the Professor held the Kelvin Chair of Electrical Engineering at Brendon University, from which he was granted indefinite leave of absence to carry out his researches. In these he was joined by the late Dr Clayton, sometime Chief Geologist to the Ministry of Fuel and Power. Their joint research was financed by grants from the Paul Fund and the Royal Society.

The Professor hoped to develop sonar as a means of precise geological surveying. Sonar, as you will know, is the acoustic equivalent of radar, and although less familiar is older by some millions of years, since bats use it very effectively to detect insects and obstacles at night. Professor Hancock intended to send high-powered supersonic pulses into the ground and to build up from the returning echoes an image of what lay beneath. The picture would be displayed on a cathode ray tube and the whole system would be exactly analogous to the type of radar used in aircraft to show the ground through cloud.

In 1957 the two scientists had achieved a partial success but had exhausted their funds. Early in 1958 they applied directly to the government for a block grant. Dr Clayton pointed out the immense value of a device which would enable us to take a kind of X-ray photo of the Earth’s crust, and the Minister of Fuel gave it his approval before passing on the application to us. At that time the report of the Bernal Committee had just been published and we were very anxious that deserving cases should be dealt with quickly to avoid further criticisms. I went to see the Professor at once and submitted a favourable report; the first payment of our grant (S/543A/68) was made a few days later. From that time I have been continually in touch with the research and have assisted to some extent with technical advice.

The equipment used in the experiments is complex, but its principles are simple. Very short but extremely powerful pulses of supersonic waves are generated by a special transmitter which revolves continuously in a pool of a heavy organic liquid. The beam produced passes into the ground and ‘scans’ like a radar beam searching for echoes. By a very ingenious time-delay circuit which I will resist the temptation to describe, echoes from any depth can be selected and so pictures of the strata under investigation can be built up on a cathode ray screen in the normal way.

When I first met Professor Hancock his apparatus was rather primitive, but he was able to show me the distribution of rock down to a depth of several hundred feet and we could see quite clearly a part of the Bakerloo Line which passed very near his laboratory. Much of the Professor’s success was due to the great intensity of his supersonic bursts; almost from the beginning he was able to generate peak powers of several hundred kilowatts, nearly all of which was radiated into the ground. It was unsafe to remain near the transmitter, and I noticed that the soil became quite warm around it. I was rather surprised to see large numbers of birds in the vicinity, but soon discovered that they were attracted by the hundreds of dead worms lying on the ground.

At the time of Dr Clayton’s death in 1960, the equipment was working at a power level of over a megawatt and quite good pictures of strata a mile down could be obtained. Dr Clayton had correlated the results with known geographical surveys, and had proved beyond doubt the value of the information obtained.

Dr Clayton’s death in a motor accident was a great tragedy. He had always exerted a stabilising influence on the Professor, who had never been much interested in the practical applications of his work. Soon afterward I noticed a distinct change in the Professor’s outlook, and a few months later he confided his new ambitions to me. I had been trying to persuade him to publish his results (he had already spent over £50,000 and the Public Accounts Committee was being difficult again), but he asked for a little more time. I think I can best explain his attitude by his own words, which I remember very vividly, for they were expressed with peculiar emphasis.

‘Have you ever wondered,’ he said, ‘what the Earth really is like inside? We’ve only scratched the surface with our mines and wells. What lies beneath is as unknown as the other side of the Moon.

‘We know that the Earth is unnaturally dense—far denser than the rocks and soil of its crust would indicate. The core may be solid metal, but until now there’s been no way of telling. Even ten miles down the pressure must be thirty tons or more to the square inch and the temperature several hundred degrees. What it’s like at the centre staggers the imagination: the pressure must be thousands of tons to the square inch. It’s strange to think that in two or three years we may have reached the Moon, but when we’ve got to the stars we’ll still be no nearer that inferno four thousand miles beneath our feet.

‘I can now get recognisable echoes from two miles down, but I hope to step up the transmitter to ten megawatts in a few months. With that power, I believe the range will be increased to ten miles; and I don’t mean to stop there.’

I was impressed, but at the same time I felt a little sceptical.

‘That’s all very well,’ I said, ‘but surely the deeper you go the less there’ll be to see. The pressure will make any cavities impossible, and after a few miles there will simply be a homogeneous mass getting denser and denser.’

‘Quite likely,’ agreed the Professor. ‘But I can still learn a lot from the transmission characteristics. Anyway, we’ll see when we get there!’

That was four months ago; and yesterday I saw the result of that research. When I answered his invitation the Professor was clearly excited, but he gave me no hint of what, if anything, he had discovered. He showed me his improved equipment and raised the new receiver from its bath. The sensitivity of the pickups had been greatly improved, and this alone had effectively doubled the range, altogether apart from the increased transmitter power. It was strange to watch the steel framework slowly turning and to realise that it was exploring regions, which, in spite of their nearness, man might never reach.

When we entered the hut containing the display equipment, the Professor was strangely silent. He switched on the transmitter, and even though it was a hundred yards away I could feel an uncomfortable tingling. Then the cathode ray tube lit up and the slowly revolving timebase drew the picture I had seen so often before. Now, however, the definition was much improved owing to the increased power and sensitivity of the equipment. I adjusted the depth control and focused on the Underground, which was clearly visible as a dark lane across the faintly luminous screen. While I was watching, it suddenly seemed to fill with mist and I knew that a train was going through.

Presently I continued the descent. Although I had watched this picture many times before, it was always uncanny to see great luminous masses floating toward me and to know that they were buried rocks—perhaps the debris from the glaciers of fifty thousand years ago. Dr Clayton had worked out a chart so that we could identify the various strata as they were passed, and presently I saw that I was through the alluvial soil and entering the great clay saucer which traps and holds the city’s artesian water. Soon that too was passed, and I was dropping down through the bedrock almost a mile below the surface.

The picture was still clear and bright, though there was little to see, for there were now few changes in the ground structure. The pressure was already rising to a thousand atmospheres; soon it would be impossible for any cavity to remain open, for the rock itself would begin to flow. Mile after mile I sank, but only a pale mist floated on the screen, broken sometimes when echoes were returned from pockets or lodes of denser material. They became fewer and fewer as the depth increased—or else they were now so small that they could no longer be seen.

The scale of the picture was, of course, continually expanding. It was now many miles from side to side, and I felt like an airman looking down upon an unbroken cloud ceiling from an enormous height. For a moment a sense of vertigo seized me as I thought of the abyss into which I was gazing. I do not think that the world will ever seem quite solid to me again.

At a depth of nearly ten miles I stopped and looked at the Professor. There had been no alteration for some time, and I knew that the rock must now be compressed into a featureless, homogeneous mass. I did a quick mental calculation and shuddered as I realised that the pressure must be at least thirty tons to the square inch. The scanner was revolving very slowly now, for the feeble echoes were taking many seconds to struggle back from the depths.

‘Well, Professor,’ I said, ‘I congratulate you. It’s a wonderful achievement. But we seem to have reached the core now. I don’t suppose there’ll be any change from here to the centre.’

He smiled a little wryly. ‘Go on,’ he said. ‘You haven’t finished yet.’

There was something in his voice that puzzled and alarmed me. I looked at him intently for a moment; his features were just visible in the blue-green glow of the cathode ray tube.

‘How far down can this thing go?’ I asked, as the interminable descent started again.

‘Fifteen miles,’ he said shortly. I wondered how he knew, for the last feature I had seen at all clearly was only eight miles down. But I continued the long fall through the rock, the scanner turning more and more slowly now, until it took almost five minutes to make a complete revolution. Behind me I could hear the Professor breathing heavily, and once the back of my chair gave a crack as his fingers gripped it.

Then, suddenly, very faint markings began to reappear on the screen. I leaned forward eagerly, wondering if this was the first glimpse of the world’s iron core. With agonising slowness the scanner turned through a giant angle, then another. And then—

I leaped suddenly out of the chair, cried ‘My God!’ and turned to face the Professor. Only once before in my life had I received such an intellectual shock—fifteen years ago, when I had accidentally turned on the radio and heard of the fall of the first atomic bomb. That had been unexpected, but this was inconceivable. For on the screen had appeared a grid of faint lines, crossing and recrossing to form a perfectly symmetrical lattice.

I know that I said nothing for many minutes, for the scanner made a complete revolution while I stood frozen with surprise. Then the Professor spoke in a soft, unnaturally calm voice.

‘I wanted you to see it for yourself before I said anything. That picture is now thirty miles in diameter, and those squares are two or three miles on a side. You’ll notice that the vertical lines converge and the horizontal ones are bent into arcs. We’re looking at part of an enormous structure of concentric rings; the centre must lie many miles to the north, probably in the region of Cambridge. How much further it extends in the other direction we can only guess.’

‘But what
is
it, for heaven’s sake?’

‘Well, it’s clearly artificial.’

‘That’s ridiculous! Fifteen miles down!’

The Professor pointed to the screen again. ‘God knows I’ve done my best,’ he said, ‘but I can’t convince myself that Nature could make anything like that.’

I had nothing to say, and presently he continued: ‘I discovered it three days ago, when I was trying to find the maximum range of the equipment. I can go deeper than this, and I rather think that the structure we can see is so dense that it won’t transmit my radiations any further.