THE MAD PLANET

by Murray Leinster

The Argosy

June 12, 1920

In All His lifetime of perhaps twenty years, it had never occurred to Burl to wonder what his grandfather had thought about his surroundings. The grandfather had come to an untimely end in a rather unpleasant fashion which Burl remembered vaguely as a succession of screams coming more and more faintly to his ears while he was being carried away at the top speed of which his mother was capable.

Burl had rarely or never thought of the old gentleman since. Surely he had never wondered in the abstract of what his great grandfather thought, and most surely of all, there never entered his head such a purely hypothetical question as the one of what his many-times-great-grandfather—say of the year 1920—would have thought of the scene in which Burl found himself.

He was treading cautiously over a brownish carpet of fungus growth, creeping furtively toward the stream which he knew by the generic title of "water." It was the only water he knew. Towering far above his head, three man-heights high, great toadstools hid the grayish sky from his sight. Clinging to the foot-thick stalks of the toadstools were still other fungi, parasites upon the growth that had once been parasites themselves.

Burl himself was a slender young man wearing a single garment twisted about his waist, made from the wing-fabric of a great moth the members of his tribe had slain as it emerged from its cocoon. His skin was fair, without a trace of sunburn. In all his lifetime he had never seen the sun, though the sky was rarely hidden from view save by the giant fungi which, with monster cabbages, were the only growing things he knew. Clouds usually spread overhead, and when they did not, the perpetual haze made the sun but an indefinitely brighter part of the sky, never a sharply edged ball of fire. Fantastic mosses, misshapen fungus growths, colossal molds and yeasts, were the essential parts of the landscape through which he moved.

Once as he had dodged through the forest of huge toadstools, his shoulder touched a cream-colored stalk, giving the whole fungus a tiny shock. Instantly, from the umbrella-like mass of pulp overhead, a fine and impalpable powder fell upon him like snow. It was the season when the toadstools sent out their spores, or seeds, and they had been dropped upon him at the first sign of disturbance.

Furtive as he was, he paused to brush them from his head and hair. They were deadly poison, as he knew well.

Burl would have been a curious sight to a man of the twentieth century. His skin was pink, like that of a child, and there was but little hair upon his body. Even that on top of his head was soft and downy. His chest was larger than his forefathers' had been, and his ears seemed almost capable of independent movement, to catch threatening sounds from any direction. His eyes, large and blue, possessed pupils which could dilate to extreme size, allowing him to see in almost complete darkness.

He was the result of the thirty thousand years' attempt of the human race to adapt itself to the change that had begun in the latter half of the twentieth century.

At about that time, civilization had been high, and apparently secure. Mankind had reached a permanent agreement among itself, and all men had equal opportunities to education and leisure. Machinery did most of the labor of the world, and men were only required to supervise its operation. All men were well-fed, all men were well-educated, and it seemed that until the end of time the earth would be the abode of a community of comfortable human beings, pursuing their studies and diversions, their illusions and their truths. Peace, quietness, privacy, freedom were universal.

Then, just when men were congratulating themselves that the Golden Age had come again, it was observed that the planet seemed ill at ease. Fissures opened slowly in the crust, and carbonic acid gas—the carbon dioxide of chemists—began to pour out into the atmosphere. That gas had long been known to be present in the air, and was considered necessary to plant life. Most of the plants of the world took the gas and absorbed its carbon into themselves, releasing the oxygen for use again.

Scientists had calculated that a great deal of the earth's increased fertility was due to the larger quantities of carbon dioxide released by the activities of man in burning his coal and petroleum. Because of those views, for some years no great alarm was caused by the continuous exhalation from the world's interior.

Constantly, however, the volume increased. New fissures constantly opened, each one adding a new source of carbon dioxide, and each one pouring into the already laden atmosphere more of the gas—beneficent in small quantities, but as the world learned, deadly in large ones.

The percentage of the heavy, vapor-like gas increased. The whole body of the air became heavier through its admixture. It absorbed more moisture and became more humid. Rainfall increased. Climates grew warmer. Vegetation became more luxuriant—but the air gradually became less exhilarating.

Soon the health of mankind began to be affected. Accustomed through long ages to breathe air rich in oxygen and poor in carbon dioxide, men suffered. Only those who lived on high plateaus or on tall mountaintops remained unaffected. The plants of the earth, though nourished and increasing in size beyond those ever seen before, were unable to dispose of the continually increasing flood of carbon dioxide.

By the middle of the twenty-first century it was generally recognized that a new carboniferous period was about to take place, when the earth's atmosphere would be thick and humid, unbreathable by man, when giant grasses and ferns would form the only vegetation.

When the twenty-first century drew to a close the whole human race began to revert to conditions closely approximating savagery. The low-lands were unbearable. Thick jungles of rank growth covered the ground. The air was depressing and enervating. Men could live there, but it was a sickly, fever-ridden existence. The whole population of the earth desired the high lands and as the low country became more unbearable, men forgot their two centuries of peace.

They fought destructively, each for a bit of land where he might live and breathe. Then men began to die, men who had persisted in remaining near sea-level. They could not live in the poisonous air. The danger zone crept up as the earth-fissures tirelessly poured out their steady streams of foul gas. Soon men could not live within five hundred feet of sea level. The low-lands went uncultivated, and became jungles of a thickness comparable only to those of the first carboniferous period.

Then men died of sheer inanition at a thousand feet. The plateaus and mountaintops were crowded with folk struggling for a foothold and food beyond the invisible menace that crept up, and up—

These things did not take place in one year, or in ten. Not in one generation, but in several. Between the time when the chemists of the International Geophysical Institute announced that the proportion of carbon dioxide in the air had increased from .04 per cent to .1 per cent and the time when at sea-level six per cent of the atmosphere was the deadly gas, more than two hundred years intervened.

Coming gradually, as it did, the poisonous effects of the deadly stuff increased with insidious slowness. First the lassitude, then the heaviness of brain, then the weakness of body. Mankind ceased to grow in numbers. After a long period, the race had fallen to a fraction of its former size. There was room in plenty on the mountaintops—but the danger-level continued to creep up.

There was but one solution. The human body would have to inure itself to the poison, or it was doomed to extinction. It finally developed a toleration for the gas that had wiped out race after race and