November the eighth, 1895, will ever be memorable in the history of Science. On that day a light，which, so far as human observation goes, never was on land or sea, was first observed. On that day, Roentgen enclosed an all-glass vacuum tube with a light-tight cardboard wrapping. He planned to place a strongly fluorescing substance, barium platinocyanide, close to the tube and observe the effect in a darkened room. In preparation, he first energized the tube to make sure that the power source and its connections did not emit sparks. Suddenly, about a yard from the tube, he saw a weak light that shimmered on a little bench he knew was located near by.... Highly excited, Röntgen lit a match and to his great surprise discovered that the source of the mysterious light was the little barium platinocyanide screen lying on the bench. He repeated the experiment again and again, each time moving the little screen farther away from the tube and each time getting the same result.