"It is that force which for years I have sought and which I have finally found. It is an electromagnetic force which repels light-rays and by curving them around the zone of force can make all matter in that zone invisible. Understand, it does not blot out light in any way, it simply makes the light-rays detour around an object and so makes that object invisible." "So much for theory. I have here a small cabinet of black metal in which is an apparatus for projecting this force upward for a few inches. Any small object placed on top of the cabinet will become invisible when the force from within is put into operation. If the force were more powerful, and radiated out in every direction instead of upward only, the cabinet itself and all around it would be made invisible." Dr. Grantham cast a quick glance around and then picked from the table a small disk-shaped paper-weight of black, opaque glass. "I shall endeavor to make this paper-weight invisible to your eyes--by placing it on the cabinet and using the force within to bend the light-rays around it." He was turning with it to the little cabinet when Carton reached forth a hand. "May I look at the thing first?" he asked. Dr. Grantham handed it to him, smiling. "Of course, and I trust you'll find nothing faked about it." The three reporters examined it closely, as did with evident interest President Ellsworth. It was quite obviously no more than a disk of the black glass used for paper-weights and inkstands. When they handed it back to Dr. Grantham he leaned forward and placed it upright in the little metal framework on the cabinet's top. It stood out there against the brilliant sunlight streaming through the window just behind it, a dead-black disk against that brilliant light. Dr. Grantham turned to the assistant. "All ready, Gray?" he queried, and the other nodded briefly. "Everything on it set," he said. "The batteries are on." "Please watch very closely," the physicist told those behind him. "These tests are rather hard to arrange, and I don't want you to have any doubts." He pressed one of the switches beneath his hands, and from the cabinet came a thin, almost inaudible whining. The three reporters and President Ellsworth were watching spellbound. A half-dozen feet before them the black disk of the paper-weight lay as dark as ever against the sunlight streaming in. But as Dr. Grantham slowly turned a small rheostat control they all uttered something like a sigh. The black disk against the sunlight was becoming translucent, transparent. It was disappearing! [Illustration: As Dr. Grantham turned the rheostat control ... the black disc against the sunlight ... began to disappear.]