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.