RONTGEN, WILHELM KONRAD VON German physicist, was born at Lennep on March 27, 1845. He received his early education in Holland, and then went to study at Zurich. He then became assistant to Mundt at Wiirzburg and afterwards at Strasbourg, becoming Privatdozent at the latter university in 1874. Next year he was appointed professor of math ematics and physics at the Agricultural Academy of Hohenheim, and in 1876 he returned to Strasbourg as extraordinary professor. In 1879 he was chosen ordinary professor of physics and director. of the Physical Institute at Giessen, whence in 1885 he removed in the same capacity to Wiirzburg. It was at the latter place that he made the discovery for which his name is chiefly known, the Röntgen rays. In 1895, while experimenting with a highly ex hausted vacuum tube on the conduction of electricity through gases, he observed the fluorescence of a barium platinocyanide screen which happened to be lying near. Further investigation showed that this radiation had the power of passing through various substances which are opaque to ordinary light, and also of affecting a photographic plate. Its behaviour being curious in
several respects, particularly in regard to reflection and refraction, doubt arose in his mind whether it was to be looked upon as light or not, and he was led to put forward the hypothesis that it was due to longitudinal vibrations in the ether, not to transverse ones like ordinary light ; but in view of the uncertainty existing as to its nature, he called it X-rays. For this discovery he received the Rumford medal of the Royal Society in 1896, jointly with Philip Lenard, who had already shown, as also had Hertz, that a portion of the cathode rays could pass through a thin film of a metal such as aluminium. Röntgen also conducted researches in various other branches of physics, including elasticity, capillarity, the ratio of the specific heats of gases, the conduction of heat in crystals, the absorption of heat-rays by different gases, piezo electricity, the electromagnetic rotation of polarized light, etc. Röntgen received the Nobel Prize for physics in 1901. He died at Munich on Feb. 1o, 1923. See also X-RAYS, NATURE OF.