In late October 1895, a few months after Halsted had unveiled the radical mastectomy in Baltimore, Wilhelm Röntgen, a lecturer at the Würzburg Institute in Germany, was working with an electron tube—a vacuum tube that shot electrons from one electrode to another—when he noticed a strange leakage. The radiant energy was powerful and invisible, capable of penetrating layers of blackened cardboard and producing a white phosphorescent glow on a barium screen accidentally left on a bench in the room.
