In all the history of scientific discovery there has never been, perhaps, so general, rapid, and dramatic an effect wrought on the scientific centres of Europe as has followed, in the past four weeks, upon an announcement made to the Würzburg Physico-Medical Society, at their December meeting, by Professor William Konrad Röntgen, professor of physics at the Royal University of Würzburg. The first news which reached London was by telegraph from Vienna to the effect that a Professor Röntgen, until then the possessor of only a local fame in the town mentioned, had discovered a new kind of light, which penetrated and photographed through everything. This news was received with a mild interest, some amusement, and much incredulity; and a week passed. Then, by mail and telegraph, came daily clear indications of the stir which the discovery was making in all the great line of universities between Vienna and Berlin. Then Röntgen's own report arrived, so cool, so business-like, and so truly scientific in character, that it left no doubt either of the truth or of the great importance of the preceding reports. To-day, four weeks after the announcement, Röntgen's name is apparently in every scientific publication issued this week in Europe; and accounts of his experiments, of the experiments of others following his method, and of theories as to the strange new force which he has been the first to observe, fill pages of every scientific journal that comes to hand. And before the necessary time elapses for this article to attain publication in America, it is in all ways probable that the laboratories and lecture-rooms of the United States will also be giving full evidence of this contagious arousal of interest over a discovery so strange that its importance cannot yet be measured, its utility be even prophesied, or its ultimate effect upon long-established scientific beliefs be even vaguely foretold. [Illustration: PICTURE OF AN ALUMINIUM CIGAR-CASE, SHOWING CIGARS WITHIN. From a photograph by A.A.C. Swinton, Victoria Street, London. Exposure, ten minutes.] [Illustration: PHOTOGRAPH OF A LADY'S HAND SHOWING THE BONES, AND A RING ON THE THIRD FINGER, WITH FAINT OUTLINES OF THE FLESH. From a photograph taken by Mr. P. Spies, director of the "Urania," Berlin.] [Illustration: THE PHYSICAL INSTITUTE, UNIVERSITY OF WÜRZBURG, WHERE PROFESSOR RÖNTGEN HAS HIS RESIDENCE, DELIVERS HIS LECTURES, AND CONDUCTS HIS EXPERIMENTS. From a photograph by G. Glock, Würzburg.]