The roar of the motor rang loud in the frosty air above a desert of ice. The sky above us was a deep purple-blue; the red sun hung like a crimson eye low in the north. Three thousand feet below, through a hazy blue mist of wind-whipped, frozen vapor, was the rugged wilderness of black ice-peaks and blizzard-carved hummocks of snow--a grim, undulating waste, black and yellow, splotched with crystal white. The icy wind howled dismally through the struts. We were flying above the weird ice-mountains of the Enderby quadrant of Antarctica.

That was a perilous flight, across the blizzard-whipped bottom of the world. In all the years of polar exploration by air, since Byrd’s memorable flights, this area had never been crossed. The intrepid Britisher, Major Meriden, with the daring American aviatrix whom the world had known as Mildred Cross before she married him, had flown into it nineteen years before--and like many others they had never returned.

Faintly, above the purring drone of the motor, I heard Ray Summers’ shout. I drew my gaze from the desolate plateau of ice below and leaned forward. His lean, fur-hooded face was turned back toward me. A mittened hand was pointing, and thin lips moved in words that I did not hear above the roar of the engine and the scream of the wind.

I turned and looked out to the right, past the shimmering silver disk of the propeller. Under the blue haze of ice-crystals in the air, the ice lay away in a vast undulating plain of black and yellow, broken with splotches of prismatic whiteness, lying away in frozen desolation to the rim of the cold violet sky. Rising against that sky I saw a curious thing.

It was a mountain of fire!

Beyond the desert of ice, a great conical peak pointed straight into the amethystine gloom of the polar heavens. It was brilliantly white, a finger of milky fire, a sharp cone of pure light. It shone with white radiance. It was brighter, far brighter, than is the sacred cone of Fujiyama in the vivid day of Japan.

For many minutes I stared in wonder at it. Far away it was; it looked very small. It was like a little heap of light poured from the hand of a fire-god. What it might be, I could not imagine. At first sight, I imagined it might be a volcano with streams of incandescent lava flowing down the side. I knew that this continent of mystery boasted Mt. Erebus and other active craters. But there was none of the smoke or lurid yellow flame which accompanies volcanic eruptions.

I was still watching it, and wondering, when the catastrophe took place--the catastrophe which hurled us into a mad extravaganza of amazing adventure.

Our little two-place amphibian was flying smoothly, through air unusually good for this continent of storms. The twelve cylinders of the motor had been firing regularly since we took off from Byrd’s old station at Little America fifteen hours before. We had crossed the pole in safety. It looked as if we might succeed in this attempt to penetrate the last white spot on the map. Then it Happened.

A sudden crack of snapping metal rang out sharp as a pistol report. A bright blade of metal flashed past the wing-struts, to fall in a flashing arc. The motor broke abruptly into a mad, deep-voiced roar.

Terrific vibration shook the ship, until I feared that it would go to pieces.

Ray Summers, with his usual quick efficiency, cut the throttle.

Quickly the motor slowed to idling speed; the vibration stopped. A last cough of the engine, and there was no sound save the shrill screaming of the wind in the gloomy twilight of this unknown land beyond the pole.

“What in the devil!” I exclaimed.

“The prop! See!” Ray pointed ahead.

I looked, and the dreadful truth flashed upon me. The steel propeller was gone, or half of it at least. One blade was broken off at a jagged line just above the hub.

“The propeller! What made it break? I’ve never heard--”

“Search me!” Ray grinned. “The important thing is that it did. It was all-metal, of course, tested and guaranteed. The guarantee isn’t worth much here. A flaw in the forging, perhaps, that escaped detection.

And this low temperature. Makes metal as brittle as glass. And the thing may have been crystallized by the vibration.”

The plane was coming down in a shallow glide. I looked out at the grim expanse of black ice-crags and glistening snow below us, and it was far from a comforting prospect. But I had a huge amount of confidence in Ray Summers. I have known him since the day he appeared, from his father’s great Arizona ranch, to be a freshman in the School of Mines at El Paso, where I was then an instructor in geology. We have knocked about queer corners of the world together for a good many years. But he is still but a great boy, with the bluff, simple manners of the West.

“Do you think we can land?” I asked.

“Looks like we’ve got to,” he said, grimly.

“And what after that?”

“How should I know? We have the sledge, tent, furs. Food, and fuel for the primus to last a week. There’s the rifle, but it must be a thousand miles to anything to shoot. We can do our best.”

“We should have had an extra prop.”

“Of course. But it was so many pounds, when every pound counted. And who knew the thing would break?”

“We’ll never get out on a week’s provisions.”

“Not a shot! Too bad to disappoint Captain Harper.” Ray grinned wanly.

“He ought to have the Albatross around there by this time, waiting for us.” The Albatross was the ship which had left us at Little America a few months before, to steam around and pick us up at our destination beyond Enderby Land. “We’re in the same boat with Major Meriden and his wife--and all those others. Lost without a trace.”

“You’ve read Scott’s diary--that he wrote after he visited the pole in 1912--the one they found with the bodies?”

“Yes. Not altogether cheerful. But we won’t be trying to get out. No use of that.” He looked at me suddenly, grinning again. “Say, Jim, why not try for that shining mountain we saw? It looks queer enough to be interesting. We ought to make it in a week.”

“I’m with you,” I said.

I did not speak again, for the jagged ice-peaks were coming rather near. I held my breath as the little plane veered around a slender black spire and dropped toward a tiny scrap of smooth snow among the ice-hummocks. I might have spared my anxiety. Under Ray’s consumately skilful piloting, the skids struck the snow with hardly a shock. We glided swiftly over the ice and came to rest just short of a yawning crevasse.

“Suppose,” said Ray, “that we spend the first night in the plane. We are tired already. We can keep warm here, and sleep. We’ve plenty of ice to melt for water. Then we’re off for the shining mountain.”

I agreed: Ray Summers is usually right. We got out the sledge, packed it, took our bearings, and made all preparations for a start to the luminous mountain, which was about a hundred miles away. The thermometer stood at twenty below, but we were comfortable enough in our furs as we ate a scanty supper and went to sleep in the cabin of the plane.

We started promptly the next morning, after draining the last of the hot chocolate from our vacuum bottles, which we left behind. We had a light but powerful sporting rifle, with telescopic sights, and several hundred rounds of ammunition. Ray put them in the pack, though I insisted that we would never need them, unless a quick way out of our predicament.

“No, Jim,” he said. “We take ‘em along. We don’t know what we’re going to find at the shining mountain.”

The air was bitterly cold as we set out: it was twenty-five below and a sharp wind was blowing. Only our toiling at the sledge kept us warm.

We covered eighteen miles that day, and made a good camp in the lee of a bare stone ridge.

That night there was a slight fall of snow. When we went on it was nearly thirty-five degrees below zero. The layer of fresh snow concealed irregularities in the ice, making our pulling very hard.

After an exhausting day we had made hardly fifteen miles.

On the following day the sky was covered with gray clouds, and a bitterly cold wind blew. We should have remained in the tent, but the shortage of food made it imperative that we keep moving. We felt immensely better after a reckless, generous fill of hot pemmican stew; but the next morning my feet were so painful from frost-bite that I could hardly get on my fur boots.

Walking was very painful to me that day, but we made a good distance, having come to smoother ice. Ray was very kind in caring for me. I became discouraged about going on at all: it was very painful, and I knew there was no hope of getting out. I tried to get some of our morphine tablets, but Ray had them, and refused to be convinced that he ought to go on without me.

On the next march we came in sight of the luminous mountain, which cheered me considerably. It was a curious thing, indeed. A straight-sided cone of light it was, rather steeper than the average volcano. Its point was sharp, its sides smooth as if cut with a mammoth plane. And it shone with a pure white light, with a steady and unchanging milky radiance. It rose out of the black and dull yellow of the ice wilderness like a white finger of hope.

The next morning it was a little warmer. Ray had been caring for my feet very attentively, but it took me nearly two hours to get on my footgear. Again I tried to get him to leave me, but he refused.

We arrived at the base of the shining mountain in three more marches.

On the last night the fuel for the primus was all gone, having been used up during the very cold weather, and we were unable to melt water to drink. We munched the last of our pemmican dry.

A few minutes after we had started on the last morning, Ray stopped suddenly.

“Look at that!” he cried.

I saw what he had seen--the wreck of an airplane, the wings crumpled up and blackened with fire. We limped up to it.

“A Harley biplane!” Ray exclaimed. “That is Major Meriden’s ship! And look at that wing! It looks like it’s been in an electric furnace!”

I examined the metal wing; saw that it had been blackened with heat.

The metal was fused and twisted.

“I’ve seen a good many wrecks, Jim. I’ve seen planes that burned as they fell. But nothing like that. The fuselage and engines were not even afire. Jim, something struck out from that shining mountain and brought them down!”

“Are they--” I began.

Ray was poking about in the snow in the cockpits.

“No. Not here. Probably would have been better for them if they had been killed in the plane. Quick and merciful.”

He examined the engines and propellers.

“No. Seems to be nothing wrong. Something struck them down!”

Soon we went on.

The shining mountain rose before us like a great cone of fire. It must have been three thousand feet high, and about that in diameter at the bottom. Its walls were as smooth and straight as though turned from milky rock crystal in a gigantic lathe. It shone with a steady, brilliantly white radiance.

“That’s no natural hill!” Ray grunted beside me as we limped on.

We were less than a mile from the foot of the cone of fire. Soon we observed another remarkable thing about it. It seemed that a straight band of silvery metal rose from the snow about its foot.

“Has it a wall around it?” I exclaimed.

“Evidently,” said Ray. “Looks as if it’s built on a round metal platform. But by whom? When? Why?”

We approached the curious wall. It was of a white metal, apparently aluminum, or a silvery alloy of that metal. In places it was twenty-five feet high, but more usually the snow and ice was banked high against it. The smooth white wall of the gleaming mountain stood several hundred yards back from the wall.

“Let’s have a look over it.” Ray suggested. “We can get up on that hummock, against it. You know, this place must have been built by men!”

We clambered up over the ice, as he suggested, until our heads came above the top of the wall.

“A lake of fire!” cried Ray.

Indeed, a lake of liquid fire lay before us. The white aluminum wall was hardly a foot thick. It formed a great circular tank, nearly a mile across, with the cone of white fire rising in the center. And the tank was filled, to within a foot of the top, with shimmeringly brilliant white fluid, bright and luminous as the cone--liquid light!

Ray dipped a hand into it. The hand came up with fingers of fire, radiant, gleaming, with shining drops falling from them. With a spasmodic effort, he flung off the luminous drops, rubbed his hand on his garments, and got it back into its fur mitten.

“Gee, it’s cold!” he muttered. “Freeze the horns off a brass billy-goat!”

“Cold light!” I exclaimed. “What wouldn’t a bottle of that stuff be worth to a chemist back in the States!”

“That cone must be a factory to make the stuff.” Ray suggested, hugging his hand. “They might pump the liquid up to the top, and then let it trickle down over the sides: that would explain why the cone is so bright. The stuff might absorb sunlight, like barium sulphide. And there could be chemical action with the air, under the actinic rays.”

“Well, if somebody’s making cold light, where does he use it?”

“I’d like to find out, and strike him for a hot meal,” Ray said, grinning. “It’s too cold to live on top of the ground around here.

They must run it down in a cave.”

“Then let’s find the hole.”

“You know it’s possible we won’t be welcome. This mountain of light may be connected with the vanishing of all the aviators. We’d better take along the rifle.”

We set off around just outside the white metal wall. The snow and ice was irregularly banked against it, but the wall itself was smooth and unbroken. We had limped along for some two miles, or more than halfway around the amazing lake of light. I had begun to doubt that we would find anything.

Then we came to a square metal tower, ten feet on a side, that rose just outside the silvery wall, to a level with its top. The ice was low here; the tower rose twenty feet above its unequal surface. We found metal flanges riveted to its side, like the steps of a ladder.

They were most inconveniently placed, nearly four feet apart; but we were able to climb them, and to look down the shaft.

It was a straight-sided pit, evidently some hundreds of feet deep. We could see a tiny square of light at the bottom, very far away. The flanges ran down the side forming the rungs of a ladder that gave access to whatever lay at the bottom.

Without hesitation, Ray climbed over the side and started down. I followed him, feeling a great relief in getting out of the freezing wind. Ray had the rifle and ammunition strapped to his back, along with a few other articles; and I had a small pack. We had abandoned the sledge, with the useless stove and the most of our instruments.

Our food was all gone.

The metal flanges were fully four feet apart, and it was not easy to scramble down from one to another; certainly not easy for one who was cold, hungry, thirsty, worn out with a week of exhausting marches, and suffering the torture of frozen feet.

“You know, this thing was not built by men,” Ray observed.

“Not built by men? What do you mean?”

“Men would have put the steps closer together. Jim, I’m afraid we are up against something--well--that we aren’t used to.”

“If men didn’t build this, what did?” I was astounded.

“Search me! This continent has been cut off from the rest of the world for geologic ages. Such life as has been found here is not common to the rest of the earth. It is not impossible that some form of life, isolated here, has developed intelligence and acquired the power to erect that cone of light--and to burn the wing off a metal airplane.”

My thoughts whirled madly as we clambered down the shaft.

It must have taken us an hour to reach the bottom. I did not count the steps, but it must have been at least a thousand feet. The air grew rapidly warmer as we descended. We both took off most of our heavy fur garments, and left them hanging on the rungs.

I was rather nervous. I felt the nearness of an intelligent, hostile power. I had a great fear that the owners of those steps would use them to find us, and then crush us ruthlessly as they had brought down Meriden’s plane.

The little square of white light below grew larger. Finally I saw Ray swing off and stand on his feet in a flood of white radiance below me.

The air was warm, moist, laden with a subtle unfamiliar fragrance that suggested growing things. Then I stood beside Ray.

We stood on the bare stone floor of a huge cavern. It must have been of volcanic origin. The walls glistened with the sparkling smoothness of volcanic glass. It was a huge space. The black roof was a hundred feet high, or more; the cave was some hundreds of feet wide. And it sloped away from us into dim distance as though leading into huger cavities below.

The light that shone upon us came from an amazing thing--a fall of liquid fire. From the roof plunged a sheer torrent of white brilliantly luminous fluid, falling a hundred feet into a shimmering pool of moon-flame. Shining opalescent mists swirled about it, and the ceaseless roar of it filled the cave with sound. It seemed that a stream of the phosphorescent stuff ran off down the cave from the pool, to light the lower caverns.

“Very clever!” said Ray. “They make the stuff up there at the cone and run it in here to see by.”

“This warm air feels mighty good,” I remarked, pulling off another garment.

Ray sniffed the air. “A curious odor. Smells like something growing.

Where anything is growing there ought to be something to eat. Let’s see what we can find.”

Only black obsidian covered the floor about us. Cautiously we skirted the overflowing pool of white fire, and followed down the stream of it that flowed toward the inner cavern. We had gone but a few hundred yards when suddenly Ray stopped me with a hand on my arm.

“Lie flat!” he hissed. “Quick!”

He dived behind a huge mass of fire-born granite. I flung myself down beside him.

“Something is coming up the trail by the shining river. And it isn’t a man! It’s between us and the light; we should be able to see it.”

Soon I heard a curious scraping sound, and a little tinkle of metal. I caught a whiff of a powerful odor--a strange, fishy odor--so strong that it almost knocked me down.

The thing that made the scraping and the tinkle and the smell came into view. The sight of it sickened me with horror.

It was far larger than a man; its body was heavy as a horse’s, but nearer the ground. In form it suggested a huge crab, though it was not very much like any crustacean I had ever seen. It was mostly red in color, and covered with a huge scarlet shell. It had five pairs of limbs. The two forward pairs had pinchers, seemingly used as hands; it scraped along on the other three pairs. Yard-long antennae, slender and luminously green, wavered above a grotesque head. The many facets of compound eyes stood on the end of foot-long stalks.

The amazing crab-thing wore a metal harness. Bands of silvery aluminum were fastened about its shell, with little cases of white metal dangling to them. In one of its uplifted claws it carried what seemed to be an aluminum bar, two feet long and an inch thick.

It scraped lumberingly past, between us and the racing stream of white fire. It passed less than a dozen feet from us. The curious fishy smell of it was overpowering, disgusting.

Sweat of horror chilled my limbs. The monster emanated power, sinister, malevolent power, power intelligent, alien and hostile to man.

I trembled with the fear that it would see us, but it scrambled grotesquely on. When it was twenty yards past, Ray picked up a block of black lava that lay beneath his hand and hurled it silently and swiftly. It crashed splinteringly on the rocks far beyond the creature, on the other side of the stream of light.

In fascination I watched the monster as it paused as if astonished.

The glittering compound eyes twisted about on their stalks, and the long shining green tentacles wavered questioningly. Then the knobbed limbs snapped the white metal tube to a level position. A metallic click came from it.

And a ray of red light, vivid and intense, burst from the tube. It flashed across the river of fire. With a dull, thudding burst it struck the rocks where the stone had fallen. It must have been a ray of concentrated heat. Rocks beneath it flashed into sudden incandescence, splintered and cracked, flowed in molten streams.

In a moment the intensely brilliant ruby ray flashed off. The rocks in the circle where it had struck faded to a dull red and then to blackness, still cracking and crumbling.

To my intense relief, the monstrous crab lumbered on.

“That,” Ray whispered, “is what got Major Meriden’s airplane wing.”

When we could hear its scraping progress no longer, we climbed up from behind our boulder and continued cautiously down the cavern, beside the rushing luminous river. In half a mile we came to a bend. Rounding it, we gazed upon a remarkable sight.

We looked into a huge cavity in the heart of the earth. A vast underground plain lay before us, with the black lava of the roof arching above it. It must have been miles across, though we had no way to measure it, and it stretched down into dim hazy distance. Its level was hundreds of feet below us.

At our feet the glistening river of fire plunged down again in a magnificent flaming fall. Below, its luminous liquid was spread out in rivers and lakes and canals, over all the vast plain. The channels ran through an amazing jungle. It was a forest of fungus, of mushroom things with great fleshy stalks and spreading circular tops. But they were not the sickly white and yellow of ordinary mushrooms, but were of brilliant colors, bright green, flaming scarlet, gold and purple-blue. Huge brilliant yellow stalks, fringed with crimson and black, lifted mauve tops thirty feet or more. It was a veritable forest of flame-bright fungus.

In the center of this weirdly forested subterranean plain was a great lake, filled, not with the flaming liquid, but with dark crystal water. And on the bottom of that lake, clearly visible from the elevation upon which we stood, was a city!

A city below the water! The buildings were upright cylinders in groups of two or three, of dozens, even of hundreds. For miles, the bottom of the great lake was covered with them. They were all of crystal, azure-blue, brilliant as cylinders turned from immense sapphires. They were vividly visible beneath the transparent water. Not one of them broke the surface.

Through the clear black water we saw moving hundreds, thousands of the giant crabs. The crawled over the hard, pebbled bottom of the lake, or swam between the crystal cylinders of the city. They were huge as the one we had seen, with red shells, great ominous looking stalked eyes, luminous green tentacular antennae and knobbed claws on forelimbs.

“Looks as if we’ve run on something to write home about,” Ray muttered in amazement.

“A whole city of them! A whole world! No wonder they could build that cone-mountain for a lighting plant!”

“When they got to knocking down airplanes with that heat-ray,” he speculated, “they were probably surprised to find that other animals had developed intelligence.”

“Do you suppose those mushroom things are good to eat?”

“We can try and see--if the crabs don’t get us first with a heat-ray.

I’m hungry enough to try anything!”

Again we cautiously advanced. The river of light fell over a sheer precipice, but we found a metal ladder spiked to the rock, with rungs as inconveniently far apart as those in the shaft. It was five hundred feet, I suppose, to the bottom; it took us many minutes to descend.

At last we stepped off in a little rocky clearing. The forest of brilliant mushrooms rose about us, great fleshy stalks of gold and graceful fringes of black and scarlet about them, with flattened heads of purple.

We started eagerly across toward the fungoid forest. I had visions of tearing off great pieces of soft, golden flesh and filling my aching stomach with it.

We were stopped by a sharp, poignantly eager human cry.

A human being, a girl, darted from among the mushroom stalks and ran across to us. Sobbing out great incoherent cries, she dropped at Ray’s feet, wrapped her arms about his knees and clung to him, while her slender body was wracked with sobbing cries.

My first impression was that she was very beautiful--and that impression I was never called upon to revise. About her lithe young body she had the merest scrap of some curious green fabric--ample in the warm air of the great cavern. Luxuriant brown hair fell loose about her white shoulders. She was not quite twenty years old, I supposed; her body was superbly formed, with the graceful curves and the free, smooth movements of a wild thing.

Ray stood motionless for a moment, thunder-struck as I was, while the sobbing girl clung to his knees. Then the astonishment on his face gave place to pity.

“Poor kid!” he murmured.

He bent, took her tenderly by the shoulder, helped her to her feet.

Her beauty burst upon us like a great light. Smoothly white, her skin was, perfect. Wide blue eyes, now appealing, even piteous, looked from beneath a wealth of golden brown hair. White teeth, straight and even, flashed behind the natural crimson of her lips.

She stood staring at Ray, in a sort of enchantment of wonder. An eager light of incredible joy flamed in her amazing eyes; red lips were parted in an unconscious smile of joy. She looked like the troubled princess in the fairy tale, when the prince of her dreams appeared in the flesh.

“God, but you’re beautiful!” Ray’s words slipped out as if he were hardly conscious of them. He flushed quickly, stepped back a little.

The girl’s lips opened. She voiced a curious cry. It was deep toned, pealing with a wonderful timbre. A happy burst of sound, like a baby makes. But strong, ringing, musically golden. And pathetically eager, pitifully glad, so that it brought tears to my eyes, cynical old man that I am.

I saw Ray wipe his eyes.

“Can you talk?” Ray put the question in a clear, deliberate voice, with great kindness ringing in it.

“Talk?” The chiming, golden voice was slow, uncertain. “Talk? Yes. I talked--with mother. But for long--I have had no need to talk.”

“Where is your mother?” Ray’s voice was gentle.

“She is gone. She was here when I was little.” The clear, silvery voice was more certain now. “Once, when I was almost as big as she--she was still. She was cold. She did not move when I called her.

The Things took her away. She was dead. She told me that sometime she would be dead.”

Bright tears came in the wide blue eyes, trickled down over the perfect face. A pathetic catch was in the deliberate, halting voice. I turned away, and Ray put a handkerchief to his face.

“What is your name? Who are you?” Ray spoke kindly.

“I am Mildred. Mildred Meriden.”

“Meriden!” Ray turned to me. “I bet this is a daughter of the major and his wife!”

“Father was the major,” the girl said slowly. “He and mother came in a machine that flew, from a far land. The Things burned the machine with the red fire. They came here and the Things kept them. They made mother sing over the water. They killed father. I never saw him.”

“I know,” Ray, said gently. “We came from the same land. We saw your father’s machine above.”

“You came from outside! And you are going back? Oh, take me with you!

Take me!” Piteous pleading was in her voice. “It is so--lonely since the Things took Mother away. Mother told me that sometime men would come, and take me away to see the people and the outside that she told me of. Oh, please take me!”

“Don’t worry! You go along whenever we leave--if we can get out.”

“Oh, I am so glad! You are very good!”

Impulsively, she threw her arms around Ray’s neck. Gently, he disengaged himself, flushing a little. I noticed, however, that he did not seem particularly displeased.

“But can we get out?”

“Mother and I tried. We could never get out. The Things watch. They make me come to the water to sing, when the great bell rings.”

“Are these things goods to eat?” I motioned to the brilliant fungal forest. I had begun to fear that Ray would never get to this very important topic.

Blue eyes regarded me. “Eat? Oh, you are hungry! Come! I have food.”

Like a child, she grasped Ray’s hand, pulled him toward the mushroom jungle. I followed, and we slipped in between the brilliantly golden, fleshy stalks. They rose to the tangle of bright feathery fringes above, huge and substantial as the trunks of trees.

In a few minutes we came to a wide, shallow canal, metal-walled, through which a slow current of the opalescent, luminous liquid was flowing. We crossed this on a narrow metal foot-bridge, and went on through the brilliant forest.