The button in the present tube was the result of nearly ten years of intensive labor. If it failed, another five to ten years would be needed to duplicate the experiment. According to his figures, Ploving felt the button capable of sending the tube no more than ten years into the future and return. The professor's plan, based upon that single assumption, was unique. Already the first wing of the new Ploving Laboratories was complete. There, in the building that would absorb nearly his entire fortune, the carefully assembled corps of young experimenters would work night and day to perfect the Ploving Button, although they could only guess at its ultimate purpose. Within ten years, if things went well, Ploving felt that a button should have been developed capable of opening the entire time-curve to the adventurous exploration of mankind. "But I'm an old man," the professor had snorted in the confidence of the little workshop. "I've no time to be dawdling about for a decade waiting for something to happen." The Ploving plan was as simple as it was astounding. He meant to use that single button already created to go ten years into the future, take the finished products of his laboratories--the Ploving Button of ten years hence--return with them to his own time and proudly present them to their creators, the technicians who were so far only fumbling with the problem of their perfection. The technicians would "save" themselves ten years of labor and the new sweeping highway into the future and the past would be open to mankind within the life of its discoverer. Only cold, inexorable logic kept the old man from insisting that he should be at the controls when the Ploving Tube met its first test. But logic was a god to whom the professor could always bow gracefully, if grudgingly, and logic certainly dictated the need for youthful co-ordination and strength during those fateful moments that could advance the scope of man's knowledge by a decade. Ploving had conveyed his decision to his younger colleague only the day before in his characteristic way. "You're elected, young man, by a unanimous vote of two." * * * * * Steve Darville, gazing past Professor Ploving to the moonlit scene beyond the window, wondered what changes ten years would have wrought. There could be little alteration in the immediate vicinity of the workshop, he knew, for the cautious professor had taken no chances. His iron law had decreed that nothing be erected or remodeled or torn away in the vicinity of the workshop; the provision, as an added precaution, being incorporated as the first item in his will. The professor fumbled with his spectacles, managed at last to place them upon his nose at an unaccustomed angle, and coughed hesitatingly. "Ready?" he asked. "Ready," Darville told him, and turned to the tube.