“This pendulum,” Robert explained, in response to the compelling and unconcealed curiosity in the professor’s eyes, “contains a rare, and hitherto unknown, element which my father named ‘mythonite.’ A good part of his life was devoted to the accumulation of this small quantity for experimental purposes. It was obtained bit by bit through a difficult and costly process from vast amounts of river-gravel, in conjunction with platinum, to which, strangely enough, it has a strong antipathy. This condition is responsible for the most curious discovery of all. The effect of gravity upon mythonite is almost entirely annulled through platinum!” “Remarkable,” said the professor; but there was a trace of incredulity in his voice which was not lost on Robert’s alert ears. “This casing,” resumed Robert, tapping on the polished side casing of the pendulum, “is a very thin layer of platinum. With the pendulum inverted, the earth’s attraction is intercepted by the casing. At the same time the attraction of any other heavenly body within the radius of the uncovered surface of the mythonite is unchanged. Further, I have discovered that the free attraction of mythonite is greatly intensified by electricity, without any corresponding increase in its gravity through the film of platinum.” He clicked on a small switch attached to the base of the frame. An odd phosphorescence suffused the disk-like surface of the pendulum. “Now, professor, will you raise the pendulum to a vertical position? Take hold of the insulated rod, here.” Professor Palmer raised the pendulum slowly. Its original weight, extraordinary as it had seemed before, was now several times greater, to his astonishment. It now seemed almost as if it were riveted into position. But gradually, as the glowing disk was pointed upward, its weight decreased. At an angle of ninety degrees its weight had virtually ceased to exist. As it neared an upright position it felt as light as a feather. In an upright position it seemed poised between the professor’s fingers as if about to take flight. He released it softly. It wavered unsteadily for a moment like a flower balancing in a light breeze, then steadied. The professor’s fingers, clumsy from pent-up excitement, collided with it. With a sudden swoop, it dropped heavily into its former pendent position, coming to rest abruptly. Professor Palmer drew a sharp breath excitedly. “Young man,” he said, extending his hand, “you have convinced me, even as I hope to convince a lot of other doubting Thomases and scoffers some day. Apparently you have evolved the greatest discovery of all time; I congratulate you.” There was no doubting his distinguished visitor’s sincerity. Robert’s voice was husky as he stammered his appreciation.