First there was the blackness of an utter void, with the cold winds of cosmic space blowing through it. Then shapes, vague, monstrous and evanescent, rolled in dim panorama through the expanse of nothingness, as if the darkness were taking material form. The winds blew and a vortex formed, a whirling pyramid of roaring blackness. From it grew Shape and Dimension; then suddenly, like clouds dispersing, the darkness rolled away on either hand and a huge city of dark green stone rose on the bank of a wide river, flowing through an illimitable plain. Through this city moved beings of alien configuration. Cast in the mold of humanity, they were distinctly not men. They were winged and of heroic proportions; not a branch on the mysterious stalk of evolution that culminated in man, but the ripe blossom on an alien tree, separate and apart from that stalk. Aside from their wings, in physical appearance they resembled man only as man in his highest form resembles the great apes. In spiritual, esthetic and intellectual development they were superior to man as man is superior to the gorilla. But when they reared their colossal city, man's primal ancestors had not yet risen from the slime of the primordial seas. These beings were mortal, as are all things built of flesh and blood. They lived, loved and died, though the individual span of life was enormous. Then, after uncounted millions of years, the Change began. The vista shimmered and wavered, like a picture thrown on a windblown curtain. Over the city and the land the ages flowed as waves flow over a beach, and each wave brought alterations. Somewhere on the planet the magnetic centers were shifting; the great glaciers and ice-fields were withdrawing toward the new poles. The littoral of the great river altered. Plains turned into swamps that stank with reptilian life. Where fertile meadows had rolled, forests reared up, growing into dank jungles. The changing ages wrought on the inhabitants of the city as well. They did not migrate to fresher lands. Reasons inexplicable to humanity held them to the ancient city and their doom. And as that once rich and mighty land sank deeper and deeper into the black mire of the sunless jungle, so into the chaos of squalling jungle life sank the people of the city. Terrific convulsions shook the earth; the nights were lurid with spouting volcanoes that fringed the dark horizons with red pillars. After an earthquake that shook down the outer walls and highest towers of the city, and caused the river to run black for days with some lethal substance spewed up from the subterranean depths, a frightful chemical change became apparent in the waters the folk had drunk for millenniums uncountable.