Henri Poincare, 1854-1912.(Courtesy of AlP Emilio Segre Visual Archives, importance for the diagnosis of kidney stones and cirrhotic livers and commented that" The surgical imagination can pleasurably lose it- self in devising endless applications of this wonderful process. "(The New-York Times, Feb 15, 1896, p 9) In the first six months after their dis. covery viennese mummies were un- dressed, doctors claimed to have pho- tographed their own brains, and the transverse ethereal vibrations: light, human heart was uncovered. By 1897 uranium rays, X rays. Uranium rays the rays'dangerous side began to were given off by certain minerals, be reported: examples included loss and they needed no apparatus to pro of hair and skin burns of varying duce them, but they shared certain everity properties with X rays. They exposed Electricians and physicists specu- photographic plates and they caused lated on the nature of these X rays. gases to conduct electricity Albert Michelson thought they British physicists weighed in on might be vortices in the ether. the side that X rays were impulses in Thomas Edison and Oliver Lodge the ether rather than continuous suggested acoustical or gravitation- waves. Lucasian Professor of Math al waves. But the rays ability to pho- ematics at Cambridge, Sir george tograph was decisive, and serious Gabriel Stokes, and his colleague and thinkers settled on three possibili- director of the Cavendish Laborato- ties, all of them of electromagnetic ry, J.J. Thomson, committed them origin: the waves were very high fre- selves to the impulse hypothesis in quency light; they were longitudinal 1896. It was consistent with their waves(Roentgens initial suggestion); conception of cathode rays as parti or they were transverse, discontin- cles(Thomson was to announce the uous impulses of the ether discovery of the corpuscle or electron Quite early on the hypothesis that one year later. )The abrupt stop of a they were longitudinal waves was charged particle would result, after a discarded, despite the support of tiny delay, in the propagation out Henri Poincare and Lord Kelvin. The ward of an electromagnetic pulse crux of the question was whether the With Thomsons exact measurement waves were polarizable. If so they of the charge-to-mass ratio and HA could not be longitudinal waves. Lorentz' successful theory of the Although the early experiments on electron, which explained many polarization were negative or unclear, intriguing phenomena, Continen- with the discovery of another ray, tal physicists began to accept, to Henri Bequerel's uranium rays for Lenard's dismay, cathode rays as which he claimed to have found po- material particles and X rays as First X ray made in public. Hand of the famed larization, those on the Continent impulses in the ether anatomist. Albert von Kolliker made durin set up a convincing typology. It went Soon new results began to Roentgen's initial lecture before the Wurzburg from lower to higher frequency come in. Two Dutch physicists, Physical Medical Society on January 23,1896 BEAM LINE 15BEAM LINE 15 importance for the diagnosis of kidney stones and cirrhotic livers and commented that “The surgical imagination can pleasurably lose it￾self in devising endless applications of this wonderful process.” (The New-York Times, Feb. 15, 1896, p. 9). In the first six months after their dis￾covery Viennese mummies were un￾dressed, doctors claimed to have pho￾tographed their own brains, and the human heart was uncovered. By 1897 the rays’ dangerous side began to be reported: examples included loss of hair and skin burns of varying severity. Electricians and physicists specu￾lated on the nature of these X rays. Albert Michelson thought they might be vortices in the ether. Thomas Edison and Oliver Lodge suggested acoustical or gravitation￾al waves. But the rays ability to pho￾tograph was decisive, and serious thinkers settled on three possibili￾ties, all of them of electromagnetic origin: the waves were very high fre￾quency light; they were longitudinal waves (Roentgen’s initial suggestion); or they were transverse, discontin￾uous impulses of the ether. Quite early on the hypothesis that they were longitudinal waves was discarded, despite the support of Henri Poincaré and Lord Kelvin. The crux of the question was whether the waves were polarizable. If so they could not be longitudinal waves. Although the early experiments on polarization were negative or unclear, with the discovery of another ray, Henri Bequerel’s uranium rays for which he claimed to have found po￾larization, those on the Continent set up a convincing typology. It went from lower to higher frequency transverse ethereal vibrations: light, uranium rays, X rays. Uranium rays were given off by certain minerals, and they needed no apparatus to pro￾duce them, but they shared certain properties with X rays. They exposed photographic plates and they caused gases to conduct electricity. British physicists weighed in on the side that X rays were impulses in the ether rather than continuous waves. Lucasian Professor of Math￾ematics at Cambridge, Sir George Gabriel Stokes, and his colleague and director of the Cavendish Laborato￾ry, J.J. Thomson, committed them￾selves to the impulse hypothesis in 1896. It was consistent with their conception of cathode rays as parti￾cles (Thomson was to announce the discovery of the corpuscle or electron one year later.) The abrupt stop of a charged particle would result, after a tiny delay, in the propagation out￾ward of an electromagnetic pulse. With Thomson’s exact measurement of the charge-to-mass ratio and H.A. Lorentz’ successful theory of the electron, which explained many intriguing phenomena, Continen￾tal physicists began to accept, to Lenard’s dismay, cathode rays as material particles and X rays as impulses in the ether. Soon new results began to come in. Two Dutch physicists, First X ray made in public. Hand of the famed anatomist, Albert von Kölliker, made during Roentgen's initial lecture before the Würzburg Physical Medical Society on January 23, 1896. Henri Poincaré, 1854–1912. (Courtesy of AIP Emilio Segrè Visual Archives)